Biology and Conservation of the Common Murre in California, Oregon, Washington, and British Columbia Volume 1: Natural History and Population Trends Information and Technology Report USGS/BRD/ITR-2000-0012 L USGS science for a changing world U.S. Department of the Interior U.S. Fish and Wildlife Service U.S. Geological Survey Technical Report Series The Biological Resources Division publisFies scientific and technical articles and reports resulting from the research performed by our scientists and partners. These articles appear in professional journals around the world. Reports are published in two report series: Biological Science Reports and Information and Technology Reports. Biological Science Reports Series Descriptions ISSN 1081-292X Information and Technology Reports ISSN 1081-2911 This series records the significant findings resulting from sponsored and co-sponsored research programs. They may include extensive data or theoretical analyses. Papers in this series are held to the same peer-review and high quahty standards as their journal counterparts. These reports are intended for publication of book-length monographs; synthesis documents; compilations of conference and workshop papers; important planning and reference materials such as strategic plans, standard of)erating procedures, protocols, handbooks, and manuals; and data compilations such as tables and bibliographies. Papers in this series are held to the same peer-review and high quality standards as their journal counterparts. Front cover photograph: Common murre (Uria aalge californica) in breeding plumage at the South Farallon Islands, California (U.S. Fish and Wildlife Service, Farallon National Wildlife Refuge). Back cover photograph: Parent-chick pair of common murres (Uria aalge californica) at sea just minutes after departing from the colony at Three Arch Rocks, Oregon, 11 July 1989 (Photo by R. W. Lowe). ^p Printed on recycled paper Suggested citation: Manuwal, D. A., H. R. Carter, T. S. Zimmerman, and D. L. Orthmeyer, Editors. 2001. Biology and conservation of the common murre in California, Oregon, Washington, and British Columbia. Volume 1 : Natural history and population trends. U.S. Geological Survey, Biological Resources Division, Information and Technology Report USGS/BRD/ITR- 2000-0012, Washington, D.C. 132 pp. Additional copies of this report may be obtained from the National Technical Information Service, 5285 Port Royal Road, Springfield, VA 22161 (1-800-553-6847 or 703-487-4650). Also available to registered users from the Defen.se Technical Infomiation Center, Attn: Help Desk, 8725 Kingman Road, Suite 0944, Fort Belvoir, VA 22060-6218 (1-800-225-3842 or 703-767-9050). Information and Technology Report 2000-001 2 December 2001 Biology and Conservation of the Common Murre in California, Oregon, Washington, and British Columbia Volume 1: Natural History and Population Trends Editors David A. Manuwal', Hany R. Carter, Tara S. Ziminennan\ and Dennis L Orthmeyer' ' University of Washington, College of Forest Resources. Wildlife Science Group Seattle, Washington 98195 ^ Humboldt State University, Department ofWildlife, Areata, California 95521 ' U.S. Fish and Wildlife Service, Division of Migratory Binds. 911 N.E. 11* Avenue Portland Oregon 97232 * U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 6924 TremontRoad, Dixon, Califomia 95620 U.S. Department of the Interior U. S. Geological Survey Washington, D. C. 20240 From the collection of International Bird Rescue Research Center Cordelia, California m association with n oP: U V m re linger ibrary efin h San Francisco, California 2006 Contents Page Contents iii Executive Summary vii Chapter 1. Natural history of the common murre {Una aalge califomica) 1 Abstract 1 Methods 3 Overview of the biology of the common murre 4 Reproductive ecology 5 Breeding habitat 5 Seasonal and daily colony attendance patterns 5 Timing of breeding 7 Egg laying 7 Incubation and hatching 8 Chick rearing and colony departure 8 Demography 9 Adult and subadult survival 9 Proportion of adults that breed 9 Hatching success 9 Fledging success 10 Breeding success 12 At-sea chick rearing 13 Philopatry, recruitment, and intercolony movements 14 Colony formation and irregular attendance 14 Predators 15 Foraging ecology 16 Diet 17 At-sea distributions 18 California 18 Oregon 19 Washington 19 British Columbia 19 Movements 20 Acknowledgments 22 Literature cited 22 Additional references 30 Unpublished data and personal communications 32 Chapter 2. Population trends of the common murre (Uria aalge califomica) 33 Abstract 33 Methods 36 Summary of population data 38 California 38 Historical background on breeding colonies in California. 1800-1978 38 Current population size and distribution of breeding colonies in California 39 Population trends in central California, 1979-1995 42 Population trends in northern California, 1979-1995 45 Oregon 48 Historical background on breeding colonies in Oregon, prior to 1980 48 Current population size and distribution of breeding colonies in Oregon 51 Population trends in Oregon, 1988-1995 52 Hi Washington 54 Historical background on breeding colonies in Washington, 1905-1978 54 Current population size and distribution of breeding colonies in Washington 56 Population trends in southern Washington, 1979-1995 59 Population trends in northern Washington, 1979-1995 60 British Columbia 61 Historical background on breeding colonies in British Columbia, 1900-1979 61 Current population size and distribution of breeding colonies in British Columbia 65 Population trends in British Columbia 65 Overall population assessment 66 Current population size and distribution of breeding colonies 66 Recent and historical population trends 68 Acknowledgments 70 Literature cited 71 Additional references 81 Unpublished data and personal communications 84 Appendix A. Techniques for aerial and other photographic surveys of common murre {Uria aalge californica) colonies in California, Oregon, Washington, and British Columbia 87 Appendix B. Histories of common murre {Uria aalge californica) colonies in California, 1800-1978 93 Appendix C. Population data for common murre {Uria aalge californica) colonies in California, 1979-1986 109 Appendix D. Population data for common murre {Uria aalge californica) colonies in California, 1987-1995 113 Appendix E. Population data for common murre {Uria aalge californica) colonies in Oregon, 1987-1995 117 Appendix F. Population data for common murre {Uria aalge californica) colonies in Washington, 1979-1989 119 Appendix G. Population data for common murre {Uria aalge californica) colonies in Washington, 1990-1995 121 Appendix H. Summary of regression analyses 123 Appendix I. Photographs of selected breeding colonies of common murres in California, Oregon, Washington, and British Columbia 129 Tables Number -; Page 1 . 1 Reproductive success of first and replacement clutches of the common murre on the South Farallon Islands, California, 1972-1983 8 1.2 Reproductive success of the common murre in the Pacific and Atlantic Oceans 1 1 1 .3 Summary of reproductive and other characteristics of the common murre in California, Oregon, Washington, and British Columbia 12 1 .4 Seasonal projected total number of common murres in the protected marine waters of Washington and southern British Columbia during 1978-1979 19 2. 1 Average and maximum sizes for nine breeding colonies of common murres in central California, 1979-1995 41 2.2 Average and maximum sizes for eight breeding colonies of common murres in northern California, 1979-1995 41 2.3 Summary of museum egg specimens of common murres in Oregon 5 1 2.4 Numbers of common murre counted at seven colonies formed in Oregon between 1989 and 1995 52 2.5 Average and maximum sizes for 15 selected breeding colonies of common murres in Oregon, 1988-1995 52 2.6 Numbers of common murres counted during replicate aerial surveys at 15 selected colonies in Oregon in 1995 53 iv 2.7 Summary of most-recent surveys of common murres at colonies in British Columbia, 1977-1997 64 2.8 Comparison of counts of common murres at subcolony sites on Triangle Island in 3 years from 1982 to 1989 65 2.9 Total sum of common murres counted and numbers of breeding adults estimated in California, Oregon. Washington, and British Columbia in 1988-1989 66 Figures Number Page 1 . 1 Common murre (Una aalge califomica) in breeding plumage at the South Farallon Islands, California 3 1 .2 Distribution of the conrunon murre on the Pacific coast of the continental United States and Canada 3 1 .3 Breeding colony of common murres in the Upper Shubrick Point study plot at the South Farallon Islands. California, May 1995 5 1 .4 Breeding colony of common murres at Puffin Rock near Triangle Island, British Columbia, 16 July 1985 5 1 .5 Reproductive success for first eggs of the conmion murre in the Upper Shubrick Point study plot at the South Farallon Islands. California. 1972-1983 10 1 .6 Parent-chick pair of common murres at sea just minutes after departing from the colony at Three Arch Rocks. Oregon. 11 July 1989 13 1 .7 Variation in diet composition of the common murre between three marine habitats and three times of year in the Gulf of the Farallones in central California. 1985-1988 17 2.1 Distribution of common murre colonies in northern California (Del Norte to Sonoma Counties) 40 2.2 Distribution of common murre colonies in central California (Marin to Monterey Counties) and southern California (Santa Barbara County) 40 2.3 Trends in whole-colony counts for six colony complexes of common murres in central California, 1979-1995 43 2.4 Trends in whole-colony counts for common murres in central California, 1979-1995 43 2.5 Changes in whole-colony counts of common murres at selected colonies in northern California, 1979-1995 46 2.6 Changes in whole-colony counts of cotmnon murres in northern California, 1979-1989, excluding the Castle Rock colony 46 2.7 Distribution of common murre colonies in Oregon (Clatsop to Curry Coimties) 49 2.8 Changes in whole-colony counts for 15 sample colonies of coirmion murres in Oregon, 1988-1995 ... 53 2.9 Distribution of common murre colonies in Washington (Clallam to Pacific Counties) 55 2.10 Trends in whole-colony counts for cotrmion murres in Washington. 1979-1995, excluding Tatoosh colonies 57 2.11 Trends in whole-colony counts for four colony complexes of common murres in Washington. 1979-1995 58 2.12 Trends in whole-colony counts for common murres in southern Washington. 1979-1995 59 2.13 Changes in whole-colony counts for common murres in northern Washington. 1979-1995 61 2.14 Distribution of common murre colonies in northern British Columbia and the southern edge of Alaska 62 2.15 Distribution of common murre colonies in southern British Columbia 62 2.16 Changes in whole-colony counts of common murres at breeding colonies in central California (all colonies), northern California (excluding the Castle Rock colony). Oregon (15 sample colonies). and Washington (excluding Tatoosh colonies), 1979-1995 68 Digitized by the Internet Archive in 2007 with funding from IVIicrosoft Corporation http://www.archive.org/details/biologyconservat01geolrich Executive Summary Over the past 30 years, the common murre (Uria aalge califomica) has been recognized as a prominent indicator of marine conservation issues in California, Oregon, Washington, and British Columbia, especially regarding oil pollution, certain fisheries, and human disturbance. To assist the effective management of the conmion murre and the marine environments in which they Uve, this summary of available information on the biology and regional status of the common murre has been sponsored by the U.S. Fish and Wildlife Service (Division of Migratory Bird Management). In Volume 1 (Chapter 1 ), the natural history of the common murre is summarized, drawing heavily on breeding studies from the South Farallon Islands. California, plus a host of detailed breeding studies from the North Atlantic Ocean. Population trends of the common murre are summarized in Volume 1 (Chapter 2), focusing on changes in whole-colony counts determined from aerial photographs between the late 1970s and 1995 in California, Oregon and Washington. Historical data and human impacts to murre colonies since the early nineteenth century are also summarized. Volume 2 will sunmiarize population threats, conservation, and management Information presented in Volume 1 has been obtained and recorded by a large number of researchers and natural historians over two centimes. From the 1960s to 1995, most work in California, Oregon, and Washington was sponsored by the U.S. Fish and WildUfe Service, Minerals Management Service, and California Department of Fish and Game. Important breeding biology studies were conducted at the South Farallon Islands (Farallon National Wildlife Refuge) by the Point Reyes Bird Observatory, in coordination with the U.S. Fish and Wildlife Service (San Francisco Bay National Wildlife Refuge). Colony siuveys in California were conducted mainly by the U.S. Fish and Wildhfe Service (San Francisco Bay National Wildlife Refuge), U.S. Geological Survey (Western Ecological Research Center, Dixon Field Station), Humboldt State University, and University of California (Santa Cruz). Colony surveys in Oregon and Washington were conducted mainly by the U.S. Fish and Wildlife Service (Oregon Coast National Wildlife Refuge and Washington Maritime National Wildhfe Refuges). In British Columbia, most work from the 1960s to 1995 was sponsored and conducted by the Canadian Wildlife Service and Royal British Columbia Museum. Key words: Alcidae. British Columbia, California, common murre, conservation, natural history, Oregon, populations, seabird, trends, Uria aalge, Washington Project Sponsor: U.S. Fish and Wildlife Service Brad J. Bortner and Tara S. Zimmerman Division of Migratory Bird Management Portland, Oregon Editorial Assistance: U.S. Geological Survey Dennis L. Orthmeyer Western Ecological Research Center Dixon Field Station Dixon, California Jerry D. Cox Upper Midwest Environmental Sciences Center Onalaska, Wisconsin Publication Costs: U.S. Fish and Wildlife Service Division of Migratory Bird Management U.S. Geological Survey Western Ecological Research Center Apex Houston Trustee Council California Department of Fish and Game, Office of Spill Prevention and Response U.S. Fish and Wildlife Service. Ecological Services, Sacramento, California National Oceanic and Atmospheric Administration Gulf of the Farallones National Marine Sanctuary USGS science for a changing world CALIFORNIA -__ I *fff9 FISH&GAME ^'^^ttEHXaf IX Chapter 1 Natural History of the Common Murre (Uria aalge californica) by David A. Manuwal' and Harry R. Carter ^University ofWashington, College of Forest Resources Wildlife Science Group Seattle. Washington 98195 ^Humboldt State University. Department of Wildlife Areata, California 95521 Abstract: This natural history of the common murre ( Uria aalge californica) in California, Oregon, Washington, and British Columbia was summarized from published and unpublished information. This information was augmented with results from studies conducted in the North Atlantic and Alaska. Substantial information on breeding biology was obtained at the South Farallon Islands in central California, and additional studies at Tatoosh Island, Washington, and Triangle Island, British Columbia. Little demographic information was available from banded populations, except at the South Farallon Islands. At-sea distribution and diet have been studied widely in California, Oregon, Washington, and British Columbia, but data were available for only a few years in many locations. Common murres breed in dense colonies on die surface of rocky islands or on cliffledges. Breeding sites are inaccessible to predatory land mammals and have low levels of human disturbance. Murres lay a single, large, pointed egg on the ground, and can lay a replacement egg if the first egg fails to hatch. The egg is incubated by both parents for 32-33 days. The chick is attended (brooded for the first few days) and fed by both parents for its first 23-24 days before it jumps into the ocean accompanied by the male parent. The parent-chick pair swims away from the colony and the chick is further raised at sea for 1-2 months by the male. At-sea chick rearing overlaps with the flightless, prebasic molt for male parents, but not for female parents or subadults. Egg laying occurs earliest (late April to early June) in California and Oregon, and later (late May to mid- August) in Washington and British Columbia. Colony attendance patterns during the prebreeding period, and early or late portions of the breeding period, tend to be more variable than between peak egg laying and peak fledging. In California, murres sporadically attend colonies in winter, and also attend colonies earlier in the prebreeding period than in Oregon, Washington, and British Columbia. Murres typically return to attend natal colonies and breed in the same locations each year. Subadult murres visit natal colonies for several years Suggested citation: Manuwal. D. A., and H. R. Carter. 2(X)1. Natural history of the conmion murre (Uria aalge californica). Pages 1-32 in D. A. Manuwal. H. R. Carter. T. S. Zimmerman, and D. L. Orthmeyer. editors. Biology and conservation of the common murre in California. Oregon. Washington, and British Columbia. Volume 1 : Namral history and population trends. U.S. Cjeological Survey, Biological Resources Division. Information and Technology Report USGS/BRD/1TR2(XX)-(X) 1 2, Washington. D.C. 2 USGS/BRD/ITR-2000-0012 before breeding for the first time at about 4—9 years of age. Annual survival rates range from 87 to 94% for adults and from 1 7 to 41 % for juveniles. Mean hatching and fledging success of first clutches at the South Farallon Islands are about 85 and 95%, respectively. Overall breeding success at this colony averages about 0.8 chicks fiedged per pair (i.e.. chicks that depart from the colony per breeding site). Additional chick mortality (not well quantified) occurs after colony departure and before chicks are independent of parental care and can fly. Harassment and predation by bald eagles (Haliaeetus leucocephalus) and peregrine falcons (Falco peregrinus) and human disturbance have reduced breeding success at some colonies. Murres are abundant at sea near major breeding colonies along the coast of central and northern California and Oregon during the breeding season, with smaller numbers (but still common) off the coast of Washington and the western and northern coasts of Vancouver Island, British Columbia. In winter, murres are most abundant in northern Washington and southern British Columbia, as well as off the coa,sts of central and northern California. Murres are uncommon in southern California and northern British Columbia during the breeding season, but are more common during winter. After departing the colony, large numbers of murres (including parent-chick pairs, females, and subadults) move northward from Oregon and Washington colonies to complete at-sea chick rearing and prebasic molt, and winter in Juan de Fuca Strait, Strait of Georgia, Puget Sound, and along the west coast of Vancouver Island. Murres from British Columbia colonies also may winter in these areas. Murres return to breeding colonies in Oregon, Washington, and British Columbia in late winter and early spring. In California, murres are largely resident year-round near breeding colonies, but some birds disperse to southern California in winter. Insufficient evidence is available to determine whether murres from Alaskan colonies winter in the area from southern British Columbia to California, although some Alaskan murres (especially from the Forrester Island colony) are present in northern British Columbia in summer and winter. Murres feed in various marine habitats on the continental shelf, from estuarine areas near shore to offshore areas. Prey varies with season and location, with fish predominating during breeding, and more euphausiids and squid during winter and prebreeding periods. Common prey species include northern anchovy (Engraulis mordax), rockfish (Sebastes spp.). Pacific sand lance (Ammodytes hexapterus), Pacitlc herring (Clupea harengus). Pacific whiting (Merluccius productus), market squid (Loligo opalescens), and euphausiids (e.g., Euphausia pacifica. Thysanoessa spinifera). Key words: Alcidae, at-sea chick rearing, at-sea distribution, breeding, British Columbia, California, colony formation, common murre, demography, diet, Farallon Islands, foraging, movements, natural history, nonbreeding, Oregon, predators, seabird, Uria aalge, Washington The common murre {Uria aalge) is a large, diving 1993). In the nineteenth and early twentieth centuries, seabird of the family Alcidae that breeds and feeds the southern subspecies was often referred to as the widely along the coasts of the northern Pacific and "California murre," either because it was then considered northern Atlantic Oceans (Figure 1 . 1 ). On the Pacific to be a separate species ( U. califomica) or the subspecies coast of North America, two subspecies currently are U. a. californica was thought to be restricted to the type recognized that breed widely from northwestern Alaska locality at the Farallon Islands, California (Sharpe 1 897; to central California (American Ornithologists' Union Coues 1903; Salomonsen 1944). Bent (1919) lumped 1 983). Some morphological differences have been noted both Pacific subspecies under Uria troille californica between the two Pacific and five Atlantic subspecies, and referred to them as "California Murres". but much overlap in measurements occurs, museum g^^^^^ (,952) assigned all breeding murres in specimens examined may be biased, and most California, Oregon and Washington to U a. californica subspecies primarily represent major world populations ^^^ remarked further that the "breeding birds of Oregon of murres in different geographic areas (Salomonsen ^^^ British Columbia are both intermediate between U. 1944; Storer 1952; Bedard 1985; Gaston and Jones ^ californica and U. a. inomata, and the amount of 1998). In the Pacific Ocean, population sizes of the overlap in size between populations is too great to permit northern subspecies {U. a. inomata) in Alaska and subspecific identification of birds of the mixed northeastern Asia are much larger than those of the wintering population. Consequently, all wintering birds southern subspecies ([/. a. californica) that ranges from ta^gn in British Columbia have been arbitrarily listed British Columbia to California (Figure 1.2; Byrd et al. under U. a. inomata/' Several other sources have BIOLOGY AND CONSERVATION OF THE COMMON MURRE 3 assigned British Columbia murres to U. a. inomata. but without additional substantiation (Guiguet 1950. 1972; Jewett et al. 1953; Gabrielson and Lincoln 1959; Drent and Guiguet 1961; Tuck 1961; Campbell et al. 1990; Morgan et al. 1991). Given poor evidence of the presence of U. a. inomata in British Columbia and little geographic separation of British Columbia and Washington colonies, we considered British Columbia breeding murres to belong to the subspecies U. a. califomica. Small numbers of murres also breed in southeast Alaska (Sowls et al. 1978). Geographic gaps are present north of southeast Alaska and between Forrester Island and British Columbia colonies; thus, we considered that breeding murres in southeast Alaska might belong to either subspecies. In this chapter, we summarize the natural history of the common murre {U. a. califomica) in California. Oregon. Washington, and British Columbia. Our goal is to provide a general summary of natural history for this species, with emphasis on basic aspects of murre biology in this geographic area. Several detailed summaries of murre biology are available or in progress (e.g.. Tuck 1961 ; Nettleship and Birkhead 1985; Gaston and Jones 1998; Ainley et al., in preparation). However, these excellent summaries focused on available published research that, for the most part, has been more extensive in the North Atlantic and Alaska and focused on certain well-studied aspects of natural history. Our intent is to provide ( 1 ) a general summary of published research with reference to representative studies, (2) information on aspects of natural history that have not been well studied, and (3) a collation of scanered unpublished information on natural history from this geographic area. We hope this approach will provide a general background on the natural history of the common murre and generate additional research in California, Oregon, Washington, and British Columbia. Methods We collated information about the natural history of the common murre from published and unpublished sources with emphasis on information from California, Oregon, Washington, and British Columbia. In this part of the range of the common murre. extensive study of the breeding biology and demography has been conducted only at the South Farallon Islands, California Rgure 1.1. Common mme{Uriaaalge califomica) in breeding plumage at the South Farallon Islands, Califomia (U.S. Fish and Wildlife Service. Farallon National Wildlife Refuge). PACIFIC OCEAN I r~1 WinlBriiig Only ! i i JYgr-round Hgure 1 2. Distribution of the common murre on the Pacific coast of the continental United States and Canada. Small numbers extend south into northern Baja Califomia. Mexico. 4 USGS/BRD/ITR-2000-0012 where the Point Reyes Bird Observatory and U.S. Fish and Wildlife Service (USFWS) have operated a long- term seabird research and monitoring program since 1972 (e.g., Ainley and Boekelheide 1990; Boekelheide et al. 1990; Sydeman 1993). Studies of breeding colonies of murres also have been conducted at Tatoosh Island, Washington, by the University of Washington during the 1990s (e.g., Parrish 1995; Parrish and Paine 1996); and Triangle Island, British Columbia, by the Canadian Wildlife Service and Simon Fraser University during some years since the 1 970s (e.g., Rodway 1 990). In addition, the USFWS, Humboldt State University, and National Audubon Society initiated studies in 1996 in central California at three colony complexes — Point Reyes, Devil's Slide, and Castle-Hurricane (Parker et al. 1997, 1998, 1999). Many important studies of the breeding biology of the common murre have been conducted in northern Europe, eastern Canada, and Alaska (see summaries in Nettleship and Birkhead 1 985; Murphy and Schauer 1994; Gaston and Jones 1998; Ainley et al., in preparation). Where necessary, we rely on studies from other parts of the range of the common murre to describe known breeding biology and demography. During the 1970s and 1980s, several Federal agencies (especially Minerals Management Service, National Oceanic and Atmospheric Administration, and the Environmental Protection Agency) sponsored major at-sea survey programs conducted by the University of California, University of Washington, and Ecological Consulting Incorporated to describe the overall abundance and distribution of seabirds in California, Oregon, and Washington in marine habitats (e.g., Wahl et al. 1981; Briggs et al. 1987, 1992). In British Columbia, at-sea surveys have been conducted in many parts of the province in the 1970s and 1980s, mainly by the Canadian Wildlife Service (e.g., Vermeer et al. 1 983; Morgan et al. 1991). We have relied extensively on these major sources to describe at-sea distribution and movements. To describe foraging ecology, diet, and other aspects of the at-sea biology of the common murre, we collated information from available studies in this geographic area and elsewhere in the world. Overview of the Biology of the Common Murre Alcids exhibit a suite of morphological, behavioral, and life-history traits characterized by wing-propelled diving, high adult survivorship, delayed maturity, and a low clutch size of one egg (except for two eggs in the genera Cepphus and Synthliboramphus). Wing-propelled diving likely evolved in alcids for efficient exploitation of subsurface marine fish and invertebrates, which are often abundant during the breeding season, may be sparse during other times of the year, and can show a high degree of annual variation. Alcids probably originated in the North Pacific Ocean (Udvardy 1963; Be'dard 1969, 1985) and radiated extensively, although there are only 23 extant species within 5 tribes (after Strauch 1985): (I) Alcini (genera Uria, Alca, and Alle), (2) Cepphini (genera Cepphus and Synthliboramphus), (3) Brachyramphini (genus Brachyramphus), (4) Aethiini (genera Aethia and Ptychoramphus), and (5) Fraterulini (genera Fratercula and Cerorhinca). Alcids have been ecologically successful and form a dominant component of breeding seabird communities in subarctic and arctic waters in the North Pacific and North Atlantic Oceans. The common murre and the thick-billed murre {Uria lomvia) are among the most abundant alcids that breed and winter throughout most of these northern waters. Alcids have strong bills for capturing, carrying, and holding prey, small wings as a compromise adaptation for diving and flying, and specialized breeding plumage (exhibited in most species). Similar to most alcids, murres exhibit a common "black above and white below" body plumage of pursuit-diving seabirds with a striking blackish-brown head plumage during the breeding season (Figure 1.1). This body plumage type may have evolved to reduce conspicuousness to potential prey when feeding in midwater, although the dark back also may assist thermal regulation along with large body size for surface breeding or retard feather wear from solar radiation (Ashmole 1971; Birkhead and Harris 1985; Cairns 1986). Unlike most alcids but like other species in the genera Uria, Cepphus, and Brachyramphus, common murres carry single prey items to their chicks and have a long bill with large palatal denticles for capturing, holding, and carrying fish (Bedard 1969). Although common murres share many similarities with other alcids, they also have evolved several different adaptations, largely related to feeding, which have produced a unique life history pattern. Three main adaptations are large body size, intermediate pattern of post-hatching development, and surface breeding in dense colonies. Common murres are the largest (800- 1300 g) of the extant alcids (Nettleship 1996). The extinct Great Auk (Piuguinus impennis) and other extinct alcids were larger but flightless. Large body size allows murres to exploit deeper water (for fish and invertebrate prey) than most other alcids. They have been recorded to dive as deep as 180 m (Piatt and Nettleship 1985). Chicks are raised partly at the colony and partly at sea, a pattern intermediate between most other alcids (Sealy 1973; Gaston 1985; Nettleship 1996; Gaston and Jones 1998). In contrast, "precocial" alcids BIOLOGY AND CONSERVATION OF THE COMMON MURRE 5 (e.g.. Ancient Murrelet Synthliboramphus antiquus) raise their chicks almost entirely at sea. and "semi- precocial" alcids (e.g., Opsin's Auklet Ptychoramphus aleuiicus) raise their chicks entirely at protected breeding sites. Common murres often breed "shoulder- to-shoulder" in large, dense colonies on the flat or sloping surface of the ground (Figure 1.3) or on cliff ledges (Figure 1 .4). Most other alcids breed in large or Figure 13. Breeding colony of common murres in the Upper Shubrick Point study plot at the South Farallon Islands. California. May 1995 (Photo by M.W.Parlcer). Figure 1.4. Breeding colony of common r. r.^ ;: -jffin Rock near Tnangle island. British Columbia, 1 6 July 1 985 (Photo by M. S. Rodway). small colonies where individual breeding sites are present on cliff ledges, in rock crevices or other cavities. or in excavated burrows. Reproductive Ecology Breeding Habitat The common murre breeds on the surface of the ground in colonies on flat, sloping, or cliff habitats on islands, or occasionally on the mainland, where breeding sites are inaccessible to mammalian predators and have low levels of human disturbance. Hat or gently sloping habitats are used only where mammalian predation is rare. For example, such habitats on small rock islands are used extensively for breeding in California, Oregon, and parts of Washington (Figure 1 .3: Boekelheide et al. 1990; Takekawa et al. 1990: Carter et al. 2001). Mammalian predation or human disturbance often limit breeding to cliff habitats in certain areas. For example, in Alaska, where foxes have been introduced to islands or are present naturally, cliff breeding predominates (Bailey 1993). Cliff-face and cliff-top breeding occurs widely and is well kno\vn at Tatoosh Island, Washington, and Triangle Island, British Columbia (Figure 1.4; Guiguet 1950; Campbell et al. 1990; Parrish 1995; Caner et al. 2001 ). In some years, cliff-top subcolonies at Tatoosh Island were subject to greater egg predation by glaucous-winged gulls (Larus glaucescens) and northwestern crows (Con'us caurinus) and greater harassment by bald eagles {Haliaeetus leucocephalus) and peregrine falcons (Falco peregrinus) than cliflf-face subcolonies (Parrish 1995, 1996). In California, Oregon, Washington, and British Columbia, breeding habitat is very stable and does not change substantially between years. However, erosion of breeding habitats has been noted at certain colonies. At the Double Point Rocks colony in central California, a small natural arch used by small numbers of breeding murres fell into the ocean between 1982 and 1985 (Takekawa et al. 1990). At the long-inactive Sea Lion Rock colony in northern California, breeding by murres has not been reported since the southern half of the rock fell into the water sometime before the 1950s (Osborne 1972). Human degradation of breeding habitats has occurred at several colonies of U. a. califomica, especially at the South Farallon Islands, Whaler Island, Rockport Rocks, and Tillamook Rock (Carter et al. 2001). Seasonal and Daily Colony Attendance Patterns The annual cycle of colony anendance is divided into three distinct periods, the breeding season, the at-sea chick-rearing period, and the nonbreeding or winter 6 USGS/BRD/ITR-2000-0012 season. Like many other seabirds, murres live entirely at sea, except for breeding-related activities at the colony, which include breeding-site prospecting and defense; courtship, pairing, and copulation; egg laying and incubation; and chick rearing. During the breeding season, breeding adults (i.e., after reaching sexual maturity and breeding for the first time) obtain a mate and breeding site, lay and incubate eggs, and brood and feed chicks at the colony. However, during severe El Nino-Southern Oscillation (hereafter "El Nino") conditions, or in response to other factors (e.g., human disturbance or severe disruption by predators), many or all murres may abandon colonies before or after egg laying. During incubation, steady numbers of birds attend breeding sites although some daily variation occurs (Boekelheide et al. 1990; Takekawa et al. 1990). At Triangle Island, British Columbia, murre numbers peaked in early evening with another lower peak in the early morning during the incubation period (Rodway 1 990). Lowest numbers occurred around mid-day ( 1 300- 1 600 h PDT). The number of murres attending colonies may decline after the median hatching date if parents spend more time away from the colony foraging for chicks. Numbers attending colonies drop sharply as chicks leave the colony (Boekelheide et al. 1990). This general pattern of attendance during the breeding season also has been observed at eastern Canadian and Alaskan colonies (Tuck 1961 ; Piatt and McLagan 1987; Hatch and Hatch 1989). At some colonies, nonbreeding subadult murres (2- 6 years old) congregate on land in "clubs" adjacent to breeding areas (Birkhead and Hudson 1977). Attendance patterns vary more at clubs than breeding areas, both within and between years, and clubs may not be present at certain colonies. Virtually nothing is known about colony attendance patterns of nonbreeding murres (i.e., subadults and nonbreeding adults) along the west coast of the United States and British Columbia. At the end of the colony chick-rearing period, successful breeding males and their partly-grown chicks depart the colony. During the at-sea chick-rearing period, chicks are fed at sea until independence. Other adults (i.e., females, failed breeders, and subadults) also cease colony attendance once male-chick pairs have departed. However, female adults may linger at breeding sites for some time, probably to defend the breeding site against prospecting birds if present (Birkhead and Nettleship 1987a). Adults and subadults undergo a flightless, prebasic molt at sea within 1-2 months of leaving the colony and develop a "mottled" or white head plumage (Birkhead and Taylor 1977). Younger subadults molt earlier than older birds in captivity and the wild (Swennen 1 977; H. R. Carter and S. G. Sealy, unpublished data). No colony attendance occurs during the at-sea chick rearing period, although sporadic attendance of breeding sites by birds that are not feeding chicks can occur at the South Farallon Islands for a short period after the colony has been largely evacuated. In the nonbreeding season, adults and possibly subadults may resume colony attendance and perform breeding-related behaviors such as site or pair-bond maintenance, or prospecting (Harris and Wanless 1988, 1989, 1990a,b). The degree of colony attendance in the nonbreeding season varies between geographic areas. No attendance occurs when murres move to wintering areas that are disjunct from colonies. A partial prealtemate molt occurs in late fall and winter when adults and subadults redevelop black head plumage, although molt in adults and older subadults precedes younger subadults (Swennen 1977). Almost all murres attending the South Farallon Islands in December- March have black heads but a few have mottled heads (Small et al. 1972). Thus, few or no younger subadults visit the colony during winter and stay at sea. In winter, California colonies are visited periodically by varying numbers of birds, starting as early, as October and extending through the winter (Ainley 1976; Sowls et al. 1980; DeGange and Sowls 1981; Boekelheide etal. 1990; Parker etal. 1997, 1998; Hastings et al. 1998; Carter et al. 2001). At the South Farallon Islands, much variation in winter attendance occurs between years because of local prey availability, weather conditions, and behavioral factors related to breeding-site attendance (Boekelheide et al. 1990; H. R. Carter, unpublished data). Fairly regular attendance begins as early as February but murres do not stay overnight at breeding sites until April, shortly before egg laying. In Oregon, murres sometimes attend colonies as early as mid-December (Bayer and Ferris 1988), but regular attendance does not occur until March-April. No information is available about winter colony attendance in Washington and British Columbia where it may not occur regularly. Murres started attending the Tatoosh Island colony area in March- April (Parrish 1995). In winter, murres often raft in waters around the South Farallon Islands before landing on the colony and, at times, rafting occurs without subsequent landings. Similar behavior also has been noted at nearshore colonies in central California (M. W. Parker, unpublished data). In spring, murres often raft in association with frequent landings on and evacuations BIOLOGY AND CONSERVATION OF THE COMMON MURRE 7 of the colony, prior to developing regular attendance during the pre-egg stage (Parrish 1995). Daily attendance patterns vary depending on the year, time of year, weather, stage of the reproductive cycle, and location of breeding colony. Variation mainly reflects the amount of time spent on the colony for breeding-related purposes versus time spent at sea. In Newfoundland, incubation shifts of common murres averaged 17 h, whereas daytime brooding shifts averaged 4 h and overnight brooding shifts averaged 12 h (Verspoor et al. 1987). Incubation and brooding shift durations did not differ between males and females, females incubated more at night than males, breeding pairs did not change over at night, and breeding pairs did not change over at the same time each day. However, shifts during chick rearing and feeding rates varied between years in response to differences in food availability (Birkhead and Nettleship 1987c; Verspoor et al. 1987). On the South Farallon Islands during 1971- 72, attendance was consistently higher in the morning than midday throughout winter and spring prior to breeding and peaked again in the evening (Boekelheide et al. 1990), although some sites were occupied all day. In winter, murres were usually absent on days with high winds or heavy rain, which is a pattern also observed in the United Kingdom (Birkhead 1978a). Attendance by thick-billed murres in arctic Canada appears linked to barometric pressure but high winds are associatedwith the approach of low pressure systems (Gaston and Nettleship 1981). Murres rarely visited colony sites on the South Farallon Islands on days with large swells, which were often associated with the passage of storm systems when air pressure changed radically (Boekelheide et al. 1990). Timing of Breeding In California, the breeding season generally occurs between late April and early August when prey are abundant in the California Current upwelling system (Briggs et al. 1988; Ainley et al. 1990; Boekelheide et al. 1990; Tyler et al. 1993). On the South Farallon Islands, first egg dates for 1972-83 were 26 April-23 May with mean dates for first eggs 9 May-9 June (Boekelheide et al. 1990). The timing of breeding in Oregon is similar to that in California with egg laying starting in early to mid-May and peaking in late May to early June (Scott 1973; R. W. Lowe, unpublished data). Breeding occurs somewhat later in Washington and British Columbia with egg laying occurring from late May to mid-August, reaching a peak in early July (Jewett et al. 1953; Vallee and Carter 1987; Campbell et al. 1990; Rodway 1990; Parrish 1995). The later breeding phenology in Washington and British Columbia may be partly related to a later availability of abundant prey resources than farther south in the California Current upwelling system (Tyler et al. 1993; Wahl et al. 1993; Murphy and Schauer 1994). Colony departure begins in late June or early July in most years at the South Farallon Islands, but did not occur until late July in 1983 during severe El Nifio conditions (Boekelheide et al. 1990; Takekawa et al. 1990). Peak departure typically occurs in early to mid-July. Colony departure begins in late June and continues during July in Oregon (Bayer et al . 1 99 1 ). At Yaquina Head, Oregon, peak fledging occurred in late July from 1969 to 1971 (Scott 1973). At Tatoosh Island, Washington, colony departure occurred from late July to early September 1991 (Parrish 1995). At Triangle Island, British Columbia, colony departure begins in mid-August and peaks in late August to early September (Vallee and Carter 1987; Rodway 1990). Egg Laying The breeding site typically is located in a depression or crack in rock, guano, or soil, and can be bordered by adjacent rocks (Figure 1 .3). On occasion, birds breed in small caves, under boulders, or under ledges. The common murre has a large single medial brood patch and incubates the single egg on the bare substrate or, at times, between and on top of its feet. No nest is built, although small stones, feathers, or other materials can be present at breeding sites. The large egg (about 1 08 g or about 1 1 % adult weight; Mahoney and Threlfall 1981; Nettleship 1996; Gaston and Jones 1998) is often brightly colored (blue or green; at times white), marked with variable amounts of dark streaks or blotches, and has a strongly-pointed ("pyriform") shape. The pointed shape of murre eggs is often cited as an apparent adaptation for breeding on narrow rock cliff ledges by reducing egg loss from accidental displacement. These eggs roll in a tight circle compared with more ovate egg shapes, especially during the late incubation period when the embryo is partly developed (Tschanz et al. 1969). Even so, many murre eggs roll away from breeding sites, sometimes accounting for most breeding failures (Tuck 1961). Other research suggests that breeding-site characteristics and incubating behavior also are important adaptations preventing egg loss (Ingold 1980; Harris and Birkhead 1985; Birkhead and Nettleship 1987b). A replacement egg will be laid by some females, if the first egg is lost. Replacement eggs are about 5-10% lighter than first eggs (Mahoney and Threlfall 1981; Gaston and Jones 1998). Replacement eggs were laid by 32% of Farallon murres that lost first eggs 8 USGS/BRD/ITR-2000-0012 (Boekelheide et al. 1990). Replacement rates of 52% and 40% have been reported in the United Kingdom and Alaska, respectively (Birkhead and Hudson 1977; Byrd et al. 1993; Murphy 1995). Eggs laid and lost early in the season are more likely to be replaced than those laid later (Uspenski 1958; Tuck 1961; Gaston and Nettleship 1981; Harris and Birkhead 1985; Boekelheide et al. 1990). The interval between loss and replacement is 14-15 days (range, 13-23 days; Boekelheide et al. 1990; Murphy 1995). On the South Farallon Islands, more than 50% of replacement eggs were laid in only 3 years (i.e., 1973, 1977, and 1981) between 1972 and 1983 (Boekelheide etal. 1990; Table 1 . 1 ). In the latter 2 years, high loss of first eggs occurred early in the season and favorable conditions for relaying extended late into the season. Incubation and Hatching Both members of a breeding pair incubate the egg. Incubating birds typically face inwards toward the face of vertical cliffs, upslope, or rock walls (Figure 1 .3), which allows for effective incubation conditions on small breeding sites on narrow ledges or within larger groups of densely-breeding birds on flat surfaces. In addition, incubating and brooding postures reduce jostling between neighboring birds and limit access by avian predators of murre eggs and chicks (e.g., gulls and corvids). Adults will retrieve eggs that roll a short distance away from breeding sites and birds occasionally incubate an egg which is not their own (Tschanz 1959). The incubation period shows little annual variation in Newfoundland ( Verspoor et al. 1987), but the incubation period was shorter for later eggs in Alaska (Murphy 1995). From 1973 through 1983, murre incubation periods at the South Farallon Islands averaged 32-33 days but ranged from 26 to 39 days (Boekelheide et al. 1990). Similar incubation periods were found for common murres in Alaska (Murphy 1 995) and for thick- billed murres in arctic Canada (Gaston and Nettleship 1 98 1 ). Based on chromosome analyses, a female to male ratio of 25: 1 7 was found for chicks at about day 20 but this ratio did not differ significantly from equality (Parker etal. 1991). Ctiicl< Rearing and Colony Departure Common murre chicks are constantly attended by at least one parent at the breeding site. During the first few days after hatching, the chick must be brooded constantly by an adult until it is able to thermoregulate. Murre chicks, on rare occasions, are brooded and fed by a nonparent adult or "helper," often a failed breeder from a neighboring site whose relationship to the chick and parents is unknown (Tschanz 1968, 1979; Birkhead 1977a; Birkhead and Nettleship 1984; Wanless and Harris 1 985 ). Tuck ( 1 96 1 ) noted that the greatest source of chick mortality was exposure during the first 6 days of life. Murre chicks develop a specialized plumage and onset of thermoregulation occurs by 10 days (Johnson and West 1975). Older chicks are not brooded constantly but attending adults protect the chick from Table 1.1. Reproductive success of first and replacement clutches of the common murre on the South Farallon Islands, California, 1 972-1 983 (from Boekelheide et al. 1990; see Figure 1 .5).' First eqqs Replacement eqfls HS Lost Addled FS HS Lost Addled FS Breeding success Year n (%) (%) (%) (%) n (%) (%) (%1 (%) (mean + SD) 1972 116 80 17 3 97 1 0 100 0 0 0.8 + 0.4 1973 135 82 18 0 93 9 67 33 0 50 0.8 ± 0.4 1974 173 88 9 3 97 3 100 0 0 100 0.9 ± 0.3 1975 137 93 4 3 98 1 100 0 0 100 0.9 ± 0.3 1976 163 90 9 2 94 3 33 66 0 0 0.8 + 0.4 1977 123 80 15 4 96 11 64 27 9 57 0.8 + 0.4 1978 123 81 15 4 85 2 50 50 0 100 0.7 ± 0.5 1979 135 83 8 9 100 5 60 20 20 66 0.8 ± 0.4 1980 144 88 9 3 98 5 60 40 0 100 0.9 ± 0.3 1981 146 89 8 3 94 9 100 0 0 78 0.9 + 0.3 1982 70 91 7 1 95 2 100 0 0 100 0.9 ± 0.3 1983 41 32 63 5 15 3 0 100 0 0 0.1 ±0.2 Total" 1,506 85 12.2 3.2 95 54 67 30 4 72 0.8 ± 0.4 "Codes: HS, hatching success (percent of eggs laid that hatch); Lost (i.e., disappeared before hatch); Addled (i.e., eggs that fail to hatch although incubated for at least 32 days); FS, fledging success (i.e., percent of chicks hatched that depart from the colony); Breeding success (i.e., number of fledglings per breeding site). "Mean percent values for 1972-82 (« = 1 1 years) excluded data in 1983 during severe El Nino conditions; however, total n values included 1983 data (/i = 12 years). BIOLOGY AND CONSERVATION OF THE COMMON MURRE 9 predators and facilitate chick feeding in dense colonies. Protection from predators also is afforded by adjacent birds in the colony that attack nearby potential predators of murre eggs and chicks (Birkhead 1977a, 1978b). Immediately after hatch, chicks grasp fish by the head end and swallow fish head first, avoiding injury from fish spines (Oberholzer and Tschanz 1%8). In the late incubation and early chick-rearing periods, parent- chick vocal recognition and chick breeding-site recognition become strongly developed which facilitates brooding, feeding, and chick return to the site if dislodged (Tschanz 1968; Wehrlin 1977). On the South Farallon Islands, a murre chick spent an average of 23-24 days at the breeding site before departing from the colony with an adult (usually the male) to complete its development at sea (see below; Boekelheide et al. 1990). Chicks hatching later and those at colonies at higher latitudes have shorter chick-rearing periods (Boekelheide et al. 1990; Murphy 1 995 ). Reduction in the time spent at the colony before departure (i.e.. chick departure from the colony when only partly grown) could have evolved in relation to decreased prey availability around the colony as the breeding season progresses, increased predation on later-hatched chicks, and reduced time remaining for the parents to complete a prebasic molt before winter (Birkhead and Harris 1985; Harris and Birkhead 1985; Wanless and Harris 1988). Several other selective pressures such as high wing loading, small prey load-carrying capacity, chick provisioning rates of breeding adults, chick growth rates on the colony and at sea, and availability of prey resources far from the colony also may have helped forge this life history pattern (Stettenheim 1959; Sealy 1973; Gaston 1985; Ydenberg 1989; Gaston and Jones 1998). Demography Adult and Subadult Survival The only long-term demographic study of the common murre in the Pacific Ocean has been conducted at the South Farallon Islands, California, where a banded sample of murres has been studied since 1985 (Sydeman 1993). Murres from a large subcolony (n = 2,500 breeding pairs) had an annual survivorship of 94%, whereas birds from a much smaller, new subcolony (n = 50 breeding pairs) survived at a rate of only 77% . This difference was attributed to high predation by peregrine falcons in winter at the latter subcolony. Annual survival rates for males and females were 99% and 93%, respectively (Sydeman 1993). Studies on common murres in the Atlantic Ocean provide demographic information that may be generally applicable to Pacific Ocean murres, despite significant differences in prey resources, hunting of miures in certain areas of the Atlantic, and various conservation issues. Band returns at or away from the colony have been used to determine adult and subadult survival rates in Europe (Birkhead 1974; Mead 1974; Hudson 1985; Hatchwell and Birkhead 1991). Adult annual survival rates of common murres ranged from 87 to 94% in five European studies. Survival rates of juveniles from the time of colony departure to breeding age varied from 17 to 41 % in 10 European studies, based mainly on band recoveries. Many hatching-year juveniles die between colony departure and during their first autumn (Birkhead 1974; Stenzel et al. 1988; Bayer et al. 1991 ). At the Isle of May, Scotland, survival of post-fledging murres decreased with later hatching date in 2 of 6 years studied (Harris et al. 1992). In diis study. \2-Al% of chicks survived to at least six months of age. which indicates that juvenile mortality also may be great in mid- to late winter. Proportion of Adults that Breed Murres breed for the first time between the ages of 4—9, with most birds recruiting between ages 5 and 7 (Hudson 1985; Harris et al. 1994; Halley et al. 1995; W. J. Sydeman, unpublished data). After reaching sexual maturity, most murres lay eggs each year, unless unusual circumstances occur. Harris and Wanless ( 1 995a) found that 5-10% of adult murres did not breed each year, owing mainly to mate loss. Sydeman (1993) noted that banded adults did not breed in 4.5% of years studied at the South Farallon Islands. During severe El Niiio events in 1982-83 and 1992-93, a large proportion of breeding adults likely did not attend colonies or attended colonies without laying eggs in California, Oregon, and Washington (Boekelheide et al. 1990; Carteret al. 2001 ). Extensive colony disturbances by humans or predators also might increase the proportion of adults that do not breed, although some birds may delay breeding or move to and breed at other colonies in response to such problems (Parrish 1995; Carter et al. 2001). Hatching Success Mean "hatching success" (i.e., percentage of eggs laid that hatch) for first eggs of Farallon murres from 1972 to 1983 was 85% (range, 80-93% in 1972-82), but was much lower in 1983 (32%) because of severe El Nino conditions (Table 1.1; Figure 1.5; Boekelheide et al. 1 990). Replacement eggs had lower hatching success, averaging 67% (range, 0-100% in 1972-82). Of 249 eggs (including first and replacement eggs) that failed in 1972-83, 58% disappeared. 20% did not hatch (after 39 days of incubation), 8% rolled away from the site. 10 USGS/BRD/ITR-2000-0012 Hatching Success AAA * rii r^ 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 Fledging Success 1*1 JH 1 972 1 973 1 974 1 975 1 976 1 977 1 978 1 979 1 980 1 98 1 1 982 1 983 Breeding Success * rh rh 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 Figure 1.5. Reproductive success for first eggs of the common murre in the Upper Shubrick Point study plot at the South Farallon Islands, California, 1972-1 983 (adapted from Boekelheideetal. 1990; see Table 1.1). Mean (± 2 standard errors) values are presented. 6% were abandoned, 3% were broken, 2% were depredated by western gulls (Larus occidentalis), 2% were dislodged during fights or interference with other murres or Brandt's cormorants {Phalacrocorax penicillatus), and 1% were wedged in rocks (Boekelheide et al. 1990). Losses from eggs rolling away from breeding sites were rarely observed at the study plot, whereas predation by western gulls was noted frequently (Spear 1993). In general, 12.2% of first eggs (n = 1,506 eggs from 1972 to 1983) and 30% of replacement eggs (n = 54 eggs from 1 972 to 1 983) were lost during incubation (Boekelheide et al. 1990). About 3.2% of all eggs {n - 1 ,560 first and replacement eggs from 1972 to 1983) failed to hatch despite being fully incubated. For 1 1 colonies in North Pacific Ocean, Byrd et al. (1993) reported mean hatching success values per colony. For first eggs, 1 1 colonies ranged between 34 and 81%. For replacement eggs, four colonies ranged between 47 and 65%. For 1 2 colonies in the Pacific and Atlantic Oceans, Murphy and Schauer (1994) also reported mean hatching success values per colony. For first eggs, 1 2 colonies ranged between 60 and 85%. For replacement eggs, eight colonies ranged between 43 and 72% (Table 1 .2). Reasons for egg loss vary between colonies, owing to many different natural and anthropogenic factors that affect breeding and feeding (e.g., Harris and Wanless 1988). A summary of reproductive and other characteristics of the common murre is presented in Table 1.3. Fledging Success Most chick deaths occur in the few days after hatching when very small chicks can be dislodged or roll away from breeding sites, especially if disturbed by humans. After six days of age, murre chicks are better able to avoid the detrimental effects of colony disturbances and are increasingly more capable of returning to natal sites if dislodged a short distance (Tuck 1961 ). In Newfoundland, chicks reaching 13 days of age had high survivorship until colony departure (greater than 80%; Burger and Piatt 1990). At the South BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 1 Farallon Islands, high "fledging success" (i.e., percent of hatched chicks that depart from the colony) occurred for chicks hatched from first eggs between 1972 and 1982 (mean = 95%; 1972-82 range, 85-100%; Table 1.1: Figure 1.5; Boekelheide et al. 1990). Chicks from replacement eggs had lower fledging success (mean = 68%; 1972-82 range. 0-100%). Very low success in 1983 (15% for first eggs with no replacement eggs laid) coincided with severe El Nino conditions and high gull predation (Boekelheide et al. 1990; Spear 1993). For 1 1 colonies in the North Pacific Ocean. Byrd et al. (1993) reported mean fledging success values per colony. For chicks hatched from first eggs. 1 1 colonies ranged between 67 and 91%. For chicks hatched from replacement eggs, four colonies ranged between 1 7 and 83%. For 12 colonies in the Pacific and Atlantic Oceans. Murphy and Schauer (1994) also reported mean fledging success values per colony (Table 1 .2). For chicks hatched from first eggs. 1 2 colonies ranged between 60 and 85%. For chicks hatched from replacement eggs, eight colonies ranged between 43 and 72%. Little quantification of chicks lost during colony departure has been attempted in available studies. Most chick losses are from predation by gulls or other avian species or injury from hitting rocks or ledges as the chicks jump off cliffs or steep slopes when leaving the colony (Tuck 1 % 1 ). Most murre fledging occurs during evening twilight, which reduces predation during colony departure and the first few hours at sea. When breeding on cliffs or steep slopes, fledging chicks flutter down from a cliff to the water at a steep angle. From low-lying or flat breeding habitats, chicks walk to the water, at times accompanied for all or a portion of the journey by an adult. At the water, they are met by an adult, usually the male parent (Scott 1990). At Three Arch Rocks, Oregon, chicks are often accompanied by an adult during their descent from the rock and immediately dive on reaching the water (R. W. Lowe, personal observation). Parent-chick recognition occurs through intense vocalizing at this time by parents and chicks. Failure to link up with the male also may contribute to chick losses at this time. Occasionally, chicks face aggression from nonparental adults on the water (Fisher and Lockley 1954: Kenyon 1959: R. W. Lowe, personal observation). At the South Farallon Islands. California sea lions (ILalophus califomianus) also may harass and prey on fledging Table 1 .2. Reproductive success of the common murre in the Pacific and Atlantic Oceans (from Murphy and Schauer 1994).' Latitude Years First Eggs Replacemen' teggs Breeding success Colony (°N) of data HS(%) FS(%) HS (%) FS \S\ (%) Source^' NE Atlantic Skomer Island 52 4 77 ±7 88 ±8 59 ±13 59 ± 18 71 ±9 1,2,3,4 Isle of May 56 6 79 ±2 94±4 55 ±8 77 ±7 78 ±4 5 Stora Karlso' 57 4 72 71 45 67 80 6 NW Atlantic Gannet Islands 54 3 85 ±4 95 ±0 43 ±7 72 ±5 83 ±3 7 E Pacific S. Farallon Islands'* 38 12 81 ± 16 89 ±23 61 ±36 63 ±42 77 ±24 8 N Pacific Chowiet Island 56 3 69 ±5 82 ±6 47 ±50 17 ±29 58 ±8 9 Agattu Island 52 2 76 + 8 88 ±10 nd nd 68 ±16 10 St. George Island*^ 57 8 73 ± 10 78 ± 19 nd nd 57 ±17 11 St. Paul Island' 57 9 73 ±8 79 ± 10 nd nd 57 ±8 12 Cape Pierce' 59 3 60±9 89 ±5 nd nd 53 ±6 13, 14 St. Lawrence Island 63 1 68 94 57 50 66 15 Bluff 65 5 65 ±4 91 ±3 72 ± \5 82 ±6 68 ± 10 16 'Values reflect means and standard deviations. Codes: HS. hatching success (i.e.. percent of eggs laid that hatch): FS. fledging success (i.e.. percent of chicks hatched that depart from the colony): breeding success (i.e., percent of chicks that depart from the colony from sites where eggs were laid); nd. no data. "Sources: 1 (Birkhead 1976b);2(Birkhead 1980):3(Hatchwell 1988):4(HatchwellandBirkhead 1991); 5 (Harris and Wanless 1988); 6 (Hedgren 1980); 7 (Birkhead and Nettleship 1987b); 8 (Boekelheide et al. 1990); 9 (Hatch and Hatch 1990): 10 (Byrd et al. 1993): 1 1 (Dragoo and Sundseth 1993); 12 (Climo 1993): 13 (Haggblom and Mendenhall 1991): 14 (Haggblom and Mendenhall 1993): 15 (Piatt etal. 1988); 16 (Murphy and Schauer 1994). 'At Stora Karlso, data were pooled between years. '^'alues for the S. Farallon Islands included all 1 2 years of data from 1 972 to 1 983 ( Boekelheide et al. 1 990; see Table 1.1). 'At St. George Island, St. Paul Island, and Cape Pierce, success was reported per site and thus included first and replacement eggs. 12 USGS/BRD/ITR-2000-0012 Table 1.3. Summary of reproductive and other characteristics of the common murre in California, Oregon, Washington, and British Columbia. Attribute Description Breeding habitat Colony attendance Breeding site Clutch size Brood patch type Replacement clutch Second clutch Incubation period Hatching success" Nestling period Fledging success" Breeding success' Colony departure At-sea rearing period Prebasic molt Prealtemate molt Adult diet Chick diet (at colony) Age at first breeding Adult survival'' Movements Open slopes and cliffs on islands; cliffs on mainland; occasionally small caves Regular attendance during breeding season; no attendance during at-sea chick rearing and prebasic molt; regular but punctuated winter attendance in central and California, rare or not known in Oregon, Washington, and British Columbia Depression or crack in surface of rock, guano, or soil 1 Single, medial Common No mean 32 days (range, 26-39; South Farallon Islands) mean 86% (range, 80-93; South Farallon Islands) mean 23 days (range, 17-35; South Farallon Islands) range 85-l(X)% (South Farallon Islands) mean 0.85 chicks per pair (range, 0.78-0.91 ; South Farallon Islands) Chick jumps off cliff, flutters, or walks to sea, accompanied by male parent Probably 1-2 months; fed and accompanied by male parent; learns to dive and capture fish before independence 1-2 months between July and November; overlaps breeding for males rearing chicks at sea; complete; remiges lost rapidly causing flightlessness 1 month between December and March; partial; black head plumage attained; flight not affected Mostly fish, some invertebrates, and squid; variable by location, sea.son, and year Fish or squid 4—15 cm in length; variable species by location and year 4-9 years; mostly 5-7 years 94% (South Farallon Islands) Oregon-Washington populations winter in northern Washington and southern British Columbia; central and northern California populations resident year-round in California; British Columbia population probably winters in British Columbia, and possibly northern Washington. ■' First egg data from 1972 to 1983,excludingyearsof poor success in 1983 or 1978 (Table 1 . 1 ; Boekelheide et al. 1990). '' Data for a new subcolony (77%) were excluded. murre chicks on occasion (W. J. Sydeman, personal communication). Gull predation at some colonies can be high during fledging. Often, however, the number of deaths has been difficult to ascertain because of low light levels. Breeding Success For 10 colonies in the North Pacific Ocean, Byrd et al. (1993) reported mean breeding success values (i.e., percent of chicks that depart from the colony from sites where eggs were laid or fledglings per breeding pair or site), which ranged between 27 and 77%. For 12 colonies in the Pacific and Atlantic Oceans, Murphy and Schauer ( 1 994) also reported mean breeding success values per colony, which ranged between 53 and 83% (Table 1 .2). Breeding success did not appear to vary much with latitude. At the South Farallon Islands, relatively high average success has been found compared to other locations. Murres averaged 0.8 chicks per site (or about 80%) from 1972 to 1982 (range, 0.7-0.9 chicks per site), but much lower site success occurred in 1 983 (0. 1 chicks per site) during severe El Nino conditions (Table 1.1; Figure 1.5; Boekelheide et al. 1990). Breeding success is affected by many natural and anthropogenic factors, including prey resources within foraging distances of colonies, predators, other breeding seabirds at the colony, human disturbance, and mortality. High breeding success of murres at the South Farallon Islands in 1972-82 reflected adequate prey resources and low impacts from natural predators, human disturbance, and human-caused mortality at sea (Boekelheide et al. 1990; Takekawa et al. 1990; Carter et al. 2001 ). In contrast, heavy predation and disturbance by eagles and falcons as well as other factors resulted in lower breeding success at Tatoosh Island, Washington. (Parrish 1995). Reduced breeding success during severe El Niiio events in 1982-83 and 1992-93 occurred widely at murre colonies in California, Oregon, Washington, and British Columbia (Boekelheide et al. 1990; Takekawa et al. 1990; Bayer et al. 1991; Wilson 1991; Carter et al. 2001). Severe El Nino events apparently resulted in poor prey conditions, which greatly impacted the proportion of adults that breed and breeding conditions for adults that laid eggs. Extensive colony disturbances by humans and predators also has reduced breeding success at certain BIOLOGY AND CONSERVATION OF THE COMMON MURRE 13 colonies in the last two decades (Parrish 1995; Carter et al. 2001). In addition to the factors noted above, breeding success probably increases with age, at least up to ages 6-9, as found in the thick-billed murre (Gaston et al. 1994). The size and density of murre colonies or breeding groups also are known to affect the reproduction of murres. At Skomer Island, Wales, breeding success was higher in dense breeding groups than small scattered groups because of high egg-laying synchrony and lower exposure to gull predation (Birkhead 1977b, 1978b). However, consistent negative relations between colony size and chick growth rate, fledging weight, and breeding success have been shown at the Pribilof Islands, Alaska, possibly because of competition and interference at breeding sites, and possibly competition for prey (Hunt et al. 1986). Whereas resource depletion around large seabird colonies has not been well demonstrated (e.g., Birkhead and Furness 1985), competition among foraging murres in dense aggregations might contribute to decreased chick growth, lower fledging weight, and possibly decreased post-fledging survival (Gaston et al. 1983; Schneider and Hunt 1984). At-sea Chick Rearing Flightless chicks leave the colony at about one quarter adult mass, before attaining complete juvenile plumage. Murre chicks are usually accompanied to sea by a single adult (Figure 1 .6), rarely by two adults (Tuck 1961; Varoujean et al. 1979; Gaston and Nettleship 1 981; Harris etal. 1990; Scott 1990). Usually, only males care for chicks at sea (Scott 1973, 1990; Birkhead 1976b; Harris and Birkhead 1985). Why male murres guard and raise chicks at sea has not been well studied and remains one of the more interesting questions in alcid biology. Figure 1.6. Parent-chick pair of common murres at sea just minutes after departing from tfie colony at Tfiree Arcfi Rocks, Oregon, 1 1 July 1989 (Photo by R.W.Lowe). Males are slightly larger than females on average (Gaston and Jones 1998) but differential chick-guarding or foraging abilities have not been demonstrated. However, females collected during the early at-sea rearing period exhibit low body weights, which may indicate poorer condition by this time (CroU 1990; H. R. Carter and S. G. Sealy, unpublished data). Females occasionally may still accompany male-chick groups (Harris et al. 1990). In 1969-73 near Yaquina Head, Oregon, Scott (1990) found that chicks were accompanied by a single adult (86.6%), two adults (2.3%), one adult and another chick (less than 1%), or were unaccompanied when observed (10.7%). Of 18 adult murres collected with chicks, 17 were male. In Barkley Sound, British Columbia, in 1979-80, 32 single adults that were accompanying chicks at sea were collected and all adults were male, based on gonad examination (H. R. Carter and S. G. Sealy, unpublished data). In two instances, another adult or subadult was strongly associated with the male-chick pair for a period of time — one was a female and the other a male (i.e., possibly the female parent or both may have been "helpers"). In 1995, USFWS personnel collected 10 adult murres that were accompanying chicks at sea off Yaquina Head and all adults were male, based on gonad examination (R. W. Lowe, unpublished data). When not feeding, chicks usually remain behind but within 2 m of an accompanying adult. Adults feed the chick for 1-2 months after fledging, although chicks learn to dive and supplement parental feeding in the latter part of the at-sea rearing period (Oberholzer and Tschanz 1969; H. R. Carter and S. G. Sealy, unpublished data). When adults dive for food, they usually surface within 75 m of the chick. Adults and chicks communicate frequently by loud calls to facilitate rapid feeding, prevent separation, and reduce kleptoparasitism or predation during feedings. Many dead chicks are washed up on beaches in the late summer and fall (Stenzel et al. 1988; Bayer et al. 1 99 1 ; Carter 1 996). South of Alaska, the largest numbers of dead chicks on beaches are found in Oregon, probably reflecting the large breeding population (Carter et al. 2001), onshore winds, and many accessible beaches. From June to September 1978-90, an annual average of 421 (range, 33-1,236) dead hatching-year murres were recorded on a 7.5-km long beach south of Newport (Bayer et al. 1991). High mortality of hatching-year murres also is sometimes recorded along the Washington coast (U. W. Wilson, personal observation). On 5 September 1979, 39 dead murres were found floating in Barkley Sound, British Columbia, after an intense storm; 36 (92.3%) were dependent chicks (none had yet achieved independence by this date), which suggests 14 USGS/BRD/ITR-2000-0012 greater susceptibility of chicks to inclement conditions than adults (H. R. Carter and S. G. Sealy, unpublished data). Overall, many of the deaths of first-year birds compared to adults (see later) seem to occur before the end of the at-sea chick-rearing period. Philopatry, Recruitment, and Intercolony Movements Like all alcids studied to date, common murres show a strong tendency to return to their natal colony to breed (Hudson 1985). Once having bred, a murre normally tends to return to the same or adjacent breeding site each year (Birkhead 1977a; Harris and Wanless 1988; Harris et al. 1 996b), and rarely moves to another colony. The process of recruitment is not well understood. Studies in Scotland (Swann and Ramsey 1983; Halley et al. 1995; Harris et al. 1996a) have shown that (I) subadults (2-7 years old) visit several parts of their natal colony before selecting a breeding site for their first breeding, usually in the same subcolony but rarely close to their natal site; (2) immatures tend to arrive progressively earlier as they become older, and are present more frequently; (3) immatures that previously visited a colony are more likely to make future visits and eventually breed at the colony site; and (4) younger immatures (i.e., 2-3 years old) mostly attended "clubs" on intertidal rocks. Over 2 years of study, 64-67% of immatures visited their natal subcolony, and 57% of murres breeding for the first time did so at their natal subcolony. For six cohorts, an average of 42-54% of chicks recruited within their natal group of 50-200 breeding pairs (Harris et al. 1996a). Little attention has been devoted to banding and resighting or retrapping murres in the Pacific Ocean. Intercolony movements have been documented at the Isle of May, Scotland. During 1987-91, Halley and Harris (1993) recorded 61 murres (2 adults and 59 immatures) on the Isle of May that had been banded elsewhere. Only one or two of these birds actually bred at the Isle of May, which suggests some inter-colony visitation, but low natal dispersal. Habitat saturation or loss, mate or site loss, colony increase or decrease, close proximity of other colonies, or human disturbance may lead to higher rates of emigration for common murres (less than 30%) or Atlantic Puffins (Fratercula arctica; less than 50%) at certain colonies (Harris and Wanless 1991; Lyngs 1993; Harris et al. 1996a). Colony Formation and irregular Attendance Since adult murres exhibit high breeding-site fidelity, high philopatry, and high annual survival rates, adult and subadult murres tend to return to and attend natal colonies each year at traditional colony locations. However, under certain circumstances, adult or subadult murres will attend other locations with suitable breeding habitats. Under favorable population conditions, murres may attempt "colony formations" (i.e., the establishment of colonies at "new" locations or the reestablishment or "recolonization" of colonies at previously-used locations). A primary hindrance to murre colony formations seems to be social factors, especially the initial process of attracting sufficient numbers of conspecifics over a period of time to encourage breeding attempts (i.e., pairing, copulation, and egg laying) at locations with suitable breeding habitat (Buckley and Buckley 1980). In addition, colony formations require adequate prey resources plus relatively low levels of human disturbance, interspecific interference, and predation. Rarely have colony formations been documented in the Pacific or Atlantic Oceans because of the infrequency of this behavior and the difficulty of detecting such events as they occur. With incomplete or unavailable information on past breeding or lack of breeding at specific colony sites, it is often impossible to distinguish between the formation of new colonies and recolonization events. Though the historical information is incomplete, it seems that natural recolonization events have occurred in northern California and Oregon, but not in central or southern California (Carter et al. 2001). Formation of colonies in northern California and Oregon have been noted mainly within "colony complexes" (Carter et al. 200 1 ) where murres apparently expanded from long-used colony sites or subcolonies to breed on nearby (i.e., within a few kilometers) unoccupied breeding habitats. Many fewer examples of colony formation away from nearby existing colonies are known. However, apparent recolonizations in Mendocino County, California, and intermittent formation of small colonies on the west coast of Vancouver Island, British Columbia, occurred long distances away from existing colonies. Murre colony formations in California and Oregon often have been associated with nesting Brandt's cormorants. In fact, murres often breed in association with nesting Brandt's cormorants in California. Oregon, and Washington (e.g., Sowls et al. 1980; Speich and Wahl 1989;Boekelheideetal. 1990; Carter etal. 1992). Cormorants may facilitate murre colony formations by providing added protection to murres from potential gull and corvid predation, as well as providing stimuli for murre breeding (McChesney et al. 1998, 1999; Sydeman et al. 1998; Carter et al. 2001). BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 5 Colony formations also can be facilitated with the use of social attraction techniques. In 1996-2000, murre decoys and broadcasted murre vocalizations were successfully used as social attraction methods at Devil's Slide Rock, California, to recolonize this previously- extirpated "colony complex" where murres no longer bred within 35^W) km of this location (Graham 1996; Parker et al. 1997. 1998, 1999; Helmuth 1999; Parker 1999; Carter etal. 2001). Several namral and anthropogenic factors can affect breeding conditions at an active colony and may contribute to colony formations by providing impetus for adults or subadults to attend other breeding habitats. Colony sites suffering from chronic impacts or persistent low numbers of attending birds may be abandoned. If such abandonment has resulted from anthropogenic factors, these colonies have been referred to as "extirpated," even though suitable breeding substrates remain. Colony extirpation has occurred for many decades at certain locations in California because of human disturbance, breeding habitat changes, and egging (Carter et al. 2001). However, it was not determined whether any surviving murres moved to other colonies or no longer bred. More recently, extirpation or abandonment of several murre colonies has occurred along the southern Washington coast, evidently because of a combination of natural and anthropogenic factors (Wilson 1991 ; Carteret al. 2001). Corresponding changes in numbers on adjacent colonies also has been noted in Washington and California, suggesting that murres will move, either temporarily or permanently, to adjacent colonies under certain circumstances (Carter et al. 2001). However, such movements and subsequent breeding have not been verified with banded birds. Irregular attendance at potential breeding habitats (and, at times, nonbreeding habitats) also has been recorded at many locations from California to British Columbia (Carter et al. 2001). Such attendance was considered to be sporadic (i.e., attendance interspersed with periods of absence) during the breeding season when regular attendance typically occurs at colonies (see above; McChesney et al. 1998). At potential breeding habitats, such behavior may reflect attendance (with or without attempted breeding) at a colony site in the process of being abandoned, extirpated, colonized, or recolonized. In Washington, irregular attendance at several colony sites and nonbreeding habitats may reflect attempts to change breeding sites, or to continue breeding at low levels under conditions of population decline (Carter et al. 2001). Predators Common murres usually breed in colonies on islands or mainland cliffs that are free of mammalian predators. On flat areas, slopes, or cliffs, murres breed in dense concentrations which reduce predation of eggs and chicks by avian predators. Other ecological adaptations which can reduce predation include large body size, constant attendance of breeding sites, and active defense of breeding sites against predators. However, surface breeding makes murres susceptible to predation of eggs and chicks by various avian predators. In California. Oregon, Washington, and British Columbia, chief predators of eggs and chicks include western gulls, glaucous-winged gulls, common ravens (Corvus corax), American crows {Corvus brachyrhynchos), northwestern crows, and occasionally brown pelicans (Pelecanus occidentalis; Boekelheide et al. 1990; Rodway 1990; Spear 1993; Parrish 1995; Parker etal. 1997, 1998: Thayer etal. 1999; R.W.Lowe, unpublished data). In Alaska and Newfoundland, Arctic foxes (Alopex lagopus) and red foxes (Vulpes vulpes) prey on murres at some colonies, which can result in colony abandonment, low reproductive success, delayed breeding, or reduced breeding attempts (Bailey 1993; Birkhead and Nettleship 1995). In California, Oregon, Washington, and British Columbia, adult and subadult murres are taken alive at or near colonies by peregrine falcons, bald eagles, other raptors (e.g., red-tailed hawk [Buteo jamaicensis]), large gulls, and occasionally marine mammals (Bayer 1986; Paine et al. 1990; Rodway 1990; Garcelon 1994; Harding 1994; Parrish 1 995, 1 996; R. W. Lowe, unpubUshed data; M. W Parker, unpublished data). However, some dead murres discovered in raptor nest remains may have been scavenged at sea or from shorelines. At some colonies, disturbances by eagles chasing or capturing murres has severely impacted breeding murres in Washington and Oregon in recent years (Sp)eich et al. 1987; Parrish 1995; Warheit 1997; Carter et al. 2001). In 1999, as much as half of the Oregon murre population may have been affected to varying degrees by eagle disturbance, compared to little if any impact before 1 994 (R. W. Lowe, unpublished data). It is unclear to what extent such disturbances occurred at these murre colonies in historical times when both eagle and murre numbers probably were higher. Current disturbances may reflect recent use by murres of breeding habitats susceptible to such disturbances at certain colonies (e.g., cliff-top habitats at Tatoosh Island) and recent expansion of eagle populations (Parrish 1995; Carteret al. 2001). 16 USGS/BRD/ITR-2000-0012 Most egg and chick predation in Farallon colonies was attributed to "specialist" western gulls that nest in or adjacent to breeding groups of murres (Spear 1 993). These gulls tend to expel other gulls from their territories and, consequently, gull predation does not necessarily increase where large numbers of gulls nest near murres, except during breeding failures and abandonments when egg loss would likely occur regardless of gull predators. Murre-specialist western gulls may not be present at small murre colonies (L. B. Spear, personal communication). Foraging Ecology Common murres forage widely between coastlines and outer parts of the continental shelf, but are most common in inshore waters (Brown 1980; Bradstreet and Brown 1985; Briggs et al. 1987). During the breeding season, foraging by breeding birds and older subadults attending colonies becomes restricted to within foraging distance of colonies, but birds still can forage as far as 200 km away from colonies (Cairns et al. 1990). In central California, murres tend to forage largely within about 35 km of breeding colonies (Briggs et al. 1987, 1988; Ainley et al. 1990, 1993; Allen 1994). However, younger subadults or adults not attending colonies can be found farther from colonies during the breeding season. In winter, murres tend to forage farther from colonies, often at distances that prevent regular colony attendance. However, winter attendance by birds at certain colonies reflects foraging within a short distance from the colony. Feeding areas, both far from and near shore, are predictable to some degree since recent studies strongly link murre at-sea densities to specific oceanographic features (Brown 1980; Woodby 1984; Schneider et al. 1990). For instance, ocean flow gradients are generated from coastline and bathymetric features (Casanady 1982; Allen et al. 1983; Schneider et al. 1990) and lead to prey aggregations at "fronts" between water types. Smaller fronts in nearshore waters can be related to local topographic features, tides, and river plumes. However, many factors contribute to prey abundance, distribution, and availability at fronts or other locations, such as locations of spawning areas and habitats of fish prey, patterns and timing of marine productivity in specific coastal areas, distance from colonies, and various effects of human activity (e.g., fisheries, pollutants, and freshwater outflow from rivers). Because of their ability to dive to great depths (up to about 1 80 m; Piatt and Nettleship 1985), murres have wide access to prey throughout a large portion of the water column and can forage along the bottom in many nearshore areas. However, common murres often forage at midwater depths, perhaps because of prey abundance, vertical distribution of prey during daylight hours, underwater energy expenditure, foraging efficiency, or differing caloric value of prey (Spring 1971; Bradstreet and Brown 1985; Birkhead and Nettleship 1987c; Ainley etal. 1996). Foraging patterns of breeding murres have been studied mainly by observing adults feeding chicks at colonies. To feed chicks, adults typically capture single prey items (usually 4-15 cm fish, but occasionally squid and invertebrates) in at-sea foraging areas and fly back to the breeding site, carrying the fish lengthwise in the bill. As the chick grows larger, feeding rates and size of fish may increase or remain the same (Burger and Piatt 1990; Hatchwell 1991; Harris and Wanless 1995b). Chick feeding rates are largely unaffected by weather, sea conditions, or chick age but high winds and heavy seas can affect adult foraging behavior (i.e., increase foraging time and effort) and reduce the size of fish fed to chicks (Birkhead 1976a; Slater 1980; Burger and Piatt 1990; Finney et al. 1999). The response of breeding murres to prey availability was studied in the Shetland Islands, Scotland, during years of high and low prey abundance (Uttley et al. 1994). In both years, murres fed on lesser sand lance {Ammodytes marinus). Between years, hatching success was similar, but the rate of chick feeding, chick growth, fledging weight, and fledging success were all higher in the year when prey were most abundant. Chick feeding frequency showed little variation during the early chick-rearing period at the colony when prey were more abundant, but increased as the breeding season progressed and prey were less abundant. When prey abundance was low, adults spent less time at the colony and their foraging trips required more than twice as much time. Murre feeding also was studied concurrently by using radio telemetry (Monaghan et al. 1994). Low prey abundance had a dramatic impact on foraging patterns ( 1 ) feeding trips were longer, (2) birds foraged more than six times farther from breeding sites, (3) birds spent more than five times as much time diving, and (4) their estimated energy expenditure was twice as great. Longer foraging time reduced time at the colony tending the chick. These changes in time allocation and energy expenditure could adversely affect chick survival at the colony and possibly adult survival after breeding. However, murres may compensate for such changes. Zador and Piatt (1999) found little difference between chick feeding rates, chick growth rates, or breeding success between increasing and declining colonies (with higher and lower prey availability, respectively) in Cook Inlet, Alaska, but time spent on the colony was greater at the increasing colony. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 17 Diet Diet information for common murres has been obtained mainly from examination of stomach contents from birds collected at sea (see summaries in Ainley and Sanger 1979; Bradstreet and Brown 1985; Sanger 1987; Vermeer et al. 1987). Even though fish are the primary prey of common murre adults and chicks, adults can feed on other types of prey with different caloric values that are less suitable for carrying to and feeding chicks (e.g.. euphausiids). Adults can eat larger fish (less than 20 cm long) than are fed to chicks with fish size limited by fish body depth (less than 40 mm; Swennen and Duiven 1977). Adult diet tends to be more diverse than chick diet in the breeding and nonbreeding seasons and. in addition to fish and squid, can include molluscs, polychaetes, and fish eggs. Diet composition varies considerably between geographic areas and times of year, including the proportion of fish and crustaceans in the diet. Overall, much less information is available on winter diet than summer diet. Various factors can affect prey abundance, availability, and location on short- and long-time scales (e.g., Ainley et al. 1993, 1994; Veil etal. 1997). In Oregon, northern anchovy (EngrauUs mordax) and rockfish {Sebastes spp.) dominated the diet throughout the year in 3 years studied, but murres consumed more euphausiids and mysids (up to about 27% of the diet by volume) in July-August (Wiens and Scott 1975; Scott 1973, 1990). Matthews (1983) also found a diverse diet in Oregon that varied between years, seasonally, and among individuals foraging in the same area. Individual murres consumed up to seven different taxa during a single foraging session. The most common prey items included anchovies, juvenile rockfish. Pacific tomcod (Microgadus proximus), whitebait smelt (Allosmerus elongatus). Pacific herring (Clupea harengus). Pacific sand lance (Ammodytes hexapterus), speckled sanddab (Citharichthys stigmaeus), mailcet squid (Loligo opalescens), crab megalops {Cancer spp.), and euphausiids. Murre diet was found to vary seasonally (i.e., prebreeding. breeding, and winter), spatially (i.e., coastal, mid-shelf, and outer-shelf waters), and between years in coastal waters near murre colonies in central California (Ainley el al. 1996; Figure 1.7). Diet was most variable during winter and in El Nino periods. During the prebreeding season (March-April), diet was dominated by euphausiids (e.g.. Euphausia pacifica and Thysanoessa spinifera) and juvenile rockfish in outer-shelf habitats. Pacific whiting (also known as Pacific hake; Merluccius pmductus) and rockfish were Figure 1.7. Variation in diet composition of the common murre between ttiree marine habitats and three times of year in the Gulf of the Farallones in central California, 1 985-1 988 (adapted from Ainley et al. 1996). Diet categories are presented as percent of total index of relative abundance (after Sanger 1 987). Diet categories are coded: EU. euphausiids. SQ, market squid [Loligo opalescent, NA, northern anchovy (EngrauUs morda4. PW. Pacific whiting [Merluccius productu^; RK. rockfish (Sebastes spp); and OT, other. Pre- Biceding (Mar-Aprt "g Bleeding g (May-Augj s WiotCT (Sep Feb) Coast ^larine Habitats Mid-Shelf Ouer-Shelf 18 USGS/BRD/ITR-2000-0012 most important in mid-shelf and coast habitats, respectively. During the breeding season (May-August), rockfish predominated in outer-shelf habitats. Pacific whiting and euphausiids were most important in mid-shelf habitats, and northern anchovy and rockfish in coast habitats. In winter (September-February), rockfish, squid, and euphausiids were important in outer-shelf habitats, whereas squid and anchovy predominated in mid-shelf and coast habitats, respectively. Throughout the year, northern anchovy were important in coast habitats, and rockfish were important in outer-shelf and coast habitats. Diet also varied by feeding location, even within a season, which suggested that if primary prey species became unavailable, murres switch feeding locations or change their diet dramatically. Rockfish and northern anchovy also are the primary prey fed to murre chicks at the South Farallon Islands (Ainley et al. 1990, 1993). Farther away from colonies in central California, rockfish, market squid, northern anchovy, night smelt (Spirinchus starksi), and ling cod {Ophiodon elongatus) were important prey in gill-net killed murres in Monterey Bay in spring, summer, and fall, but varied seasonally and between years (CroU 1990). Euphausiids were not important prey in spring and squid dominated during summer 1 983. Fish also were the principal prey in winter in Monterey Bay, although some squid were taken (Baltz and Morejohn 1977). In British Columbia, murres have been reported feeding on Pacific sand lance. Pacific herring, northern anchovy. Pacific whiting, smelts (Osmeridae), other small fish, marine crustaceans, and small squids (Munro and Clemens 1931; Guiguet 1972; H. R. Carter and S. G. Sealy, unpublished data). Murres are well known to use estuarine waters to exploit abundant Pacific herring during spring spawning (e.g.. Straits of Georgia) or in juvenile-herring rearing areas in late summer and fall (e.g., Barkley Sound; Munro and Clemens 1931; Robertson 1972; Vermeer et al. 1987; Campbell et al. 1990; H. R. Carter and S. G. Sealy, unpublished data). In gill-net killed murres in late summer and early fall 1 993- 96 in the San Juan Islands, Washington, murres fed primarily on Pacific herring. Pacific sand lance, salmonid smolts (Oncorhynchus sp.), and Pacific tomcod (Wilson and Thompson 1998). At-sea Distributions California Extensive at-sea surveys were conducted monthly from 1975 to 1978 in southern California and from 1980 to 1982 in central and northern California (Briggs et al. 1981, 1983, 1987; Tyler et al. 1993). Common mun-es were present at high densities in shelf-slope habitats near colonies in central and northern California throughout the year. During the breeding season, densities averaged 6-12 birds per km- but peaked at 20-200 birds per km- near colonies. Highest average densities (12-18 birds per km-) were recorded in late July to September, after departure of chicks and adults from colonies. Two major factors affect the use of these foraging areas: the distribution of suitable breeding habitats and the distribution and abundance of prey. In California, colonies are present in productive coastal areas with localized upwelling often located downstream from coastal promontories. These conditions probably result in abundant prey resources near colonies most of the year, allowing for year-round residency in these areas. Between January and July, small numbers of murres are found between colony areas in northern and central California (i.e., southern Humboldt to southern Sonoma Counties). Densities can increase in this area in winter (Briggs et al. 1983), apparently because of wider foraging by murres from northern California and possibly southern Oregon. In winter, lower densities of murres are present in offshore habitats in central and northern California and shelf-slope habitats in southern California that experience cool, locally upwelled waters. Very small numbers of murres winter in warmer waters in the southern part of the Southern California Bight and northern Baja California, Mexico (Unitt 1984; Howell and Webb 1995). During the breeding season in central California, virtually all murres were observed in waters 200 m or less in depth and adjacent to shore (less than 35 km from colonies; Briggs etal. 1988; Ainley etal. 1990). A large feeding area located 8-25 km northeast of the Farallon Islands was used regularly from mid-April to early June. In early spring, murres fed in deep waters at the shelf edge near the Farallon Islands. However, murres also are widely present in nearshore waters in the Gulf of the Farallones during the breeding season, as far south as northern San Luis Obispo County and as far north as southern Sonoma County (Bolander and Parmeter 1978; Roberson 1985). As the season progressed, murres began to shift toward the shallower coastal waters along the nearby mainland coast. After fledging, adult-chick groups dispersed along the coast, both south (e.g., Monterey Bay) and north (e.g.. Bodega Bay). Late summer movement of murres into Monterey Bay for at-sea chick rearing and prebasic molt are followed with movement out of the bay into offshore waters in fall (Croll 1990). During El Nifio conditions, murres feed closer to shore during summer and some traditional feeding areas BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 9 (i.e., offshore or inshore) may be abandoned when declines in oceanic productivity result in substantially fewer prey (Ainley et al. 1990: CroU 1990). Oregon At-sea distribution of murres was studied in Oregon in 1989 and 1990(Briggsetal. 1992; Tyler etal. 1993). Murres frequented the shelf-edge banks for most of the year and near-shore coastal waters were used in late summer. Numbers of murres peaked during late summer when adults and dependent chicks concentrated in coastal waters as they moved north. Shallow waters with murre concentrations coincided with the mid-shelf thermohaline fronts associated with the southward edge of the Columbia River plume (Landry et al. 1989). Murre densities from boat transects in the early 1 970s ranged from 20 to 60 birds per km- within 25 km of shore (Wiens and Scott 1975). These densities were consistent with those derived by Briggs et al. ( 1992) in southern Oregon and from northern Oregon to Grays Harbor, Washington. In general, few murres are present in Oregon during the nonbreeding season, with small number off southern Oregon and moderate numbers off northern Oregon (R. G. Ford, personal communication). Washington On the outer coast, murres feed close to shore and farther offshore, at times in waters as deep as 1 ,000- 2,500 m (Wahl 1975: Briggs et al. 1992: Wahl et al. 1993; Thompson 1997). In January, April, May, and June, murres were found mainly in water depths of 1 25- 140 m in 1989-90 (Briggs etal. 1992: Tyler etal. 1993). During the breeding season, murres fed 1 8-27 km from known colony sites. From April to May, murres were found mostly along a narrow strip close to shore where local densities varied from 24 to 240 birds per km-. In July, murres were well dispersed over most of the continental shelf. Off Grays Harbor, murres were found commonly in shallow nearshore waters (50-100 m) during summer-fall 1972-88 (Wahl 1975; Wahl et al. 1993). Moderate numbers are found off southwest Washington between November and January (R. G. Ford, personal communication). Peak numbers of murres in the protected marine waters of Washington are present in August through mid-October, after adult-chick pairs from Washington and Oregon colonies have departed from colonies and moved north (Table 1 .4; see below). For example, more than 200,000 mun^es were estimated in September 1978 (Manuwal et al. 1979; Wahl et al. 1981 ). In September 1 989-90, murres were present on the outer coast in lower densities (18-183 birds per km-), but distributed similarly to July (Briggs et al. 1992). By November, murre numbers in protected marine waters had declined substantially, indicating movement northward into Georgia Strait, British Columbia, or to outer coast areas off the entrance to Juan de Fuca Strait (Table 1 .4). British Columbia During outer coast at-sea surveys in 1 972 and 1 973, and 1981 to 1990, common murres were common in all seasons off the west coast of Vancouver Island with a lower number present farther north off the Queen Charlotte Islands (Robertson 1974; Vermeer etal. 1983, 1989: Morgan et al. 1991 ; Vermeer and Morgan 1992). In spring, murres were present in colder, less saline inshore waters, but occasionally fed far offshore. Highest densities occurred in summer-fall in shallow waters (less than 60 m) on the broad continental shelf, as well as inshore and fiord waters, off southwestern Vancouver Island between Barkley and Clayoquot sounds. The Table 1.4. Seasonal projected total number of common murres in the protected marine waters of Washington and southern British Columbia during 1978-1 979 (from Wahl etal. 1981). Spring Summer Fall Winter Area April-May June July-October November-March Western Strait of Juan de Fuca 1,400 1,200 110,000 26,000 Eastern Strait of Juan de Fuca 1,100 1,300 24,000 12,000 Admiralty Inlet 40 ") 450 1,200 Anacortes-Hales Pass 330 40 9,200 5,800 Georgia Strait-F.ast 7,400 460 9,000 17.000 Georgia Strait- West 1,300 20 70 710 Haro Strait 170 10 7,100 1,600 Rosario Strait 610 3 11,000 11,000 Northern Waters 20 — 1.700 5,300 San Juan Passages 50 40 940 2,700 San Juan's Bays 10 4 330 200 Canadian Waters* 70 1 280 2,500 Total 12,500 3,080 174,070 86.010 ' Active Pass. Gulf Islands. Sidney approach. 20 USGS/BRD/ITR-2000-0012 movement of thousands of murres into Barkley Sound, British Columbia, was documented in July-September 1979 and 1980 when this area was used extensively for at-sea chick rearing and prebasic molt (H. R. Carter and S. G. Sealy, unpublished data). At this time, murres often participated in multispecies flocks feeding on schools of Pacific herring and Pacific sand lance (Porter and Sealy 1981). In winter (November to March), murres remained abundant on the continental shelf off southwest Vancouver Island but few murres were present in nearshore and fiord waters in Barkley and Clayoquot sounds (Robertson 1974; Hatler at al. 1978; Morgan et al. 1 99 l;Vermeer and Morgan 1992; H.R.Carter and S. G. Sealy, unpublished data). Only small numbers of breeding and nonbreeding murres remained in nearshore waters in Barkley Sound in May-June (Carter and Sealy 1984; Vermeer and Morgan 1992). In late summer, fall, and winter, murres are common in protected waters and fiords in the Strait of Georgia often at small fronts and near Pacific herring spawning grounds (Brooks and Swarth 1925; Munro and Clemens 1931;Edwards 1965; Vermeer et al. 1983; Campbell et al. 1 990). Murres move out of the Strait of Georgia into either protected waters in Washington or outer coastal waters off the entrance to Juan de Fuca Strait between February and May (Vermeer 1983; Campbell et al. 1990; H. R. Carter and S. G. Sealy, unpublished data). In northern British Columbia, murres were observed in all months, but peaked in Dixon Entrance and Hecate Strait between April and May, and September and October (Vermeer and Rankin 1984, 1985; Morgan et al. 1991; Morgan 1997). Inshore waters around the Queen Charlotte Islands had higher densities in winter than in summer in 1972-73 and October 1976 than from May to June 1977 (Robertson 1974; Vermeer et al. 1983). Movements Common murre movements from specific colonies in California, Oregon, Washington, and British Columbia are poorly known because few banding programs have occurred at colonies. Large numbers of murres (2,820; 94.6% chicks) were banded at Cape Lookout and Three Arch Rocks, Oregon, from 1 930 to 1940 (Storer 1952; Tuck 1961; Bayer and Ferris 1987). Most (73%; n - 53) band recoveries of hatching-year birds occurred north of colonies in Oregon and Washington. Band recoveries began in August in Washington and September in British Columbia. No band recoveries of hatching-year murres occurred in Oregon after September. In central California, murres have been banded annually at the South Farallon Islands since 1985 and sporadically in the 1970s (Sydeman 1993; Sydeman et al. 1997). In addition, many murres that were oiled and cleaned have been banded and released (Sharp 1996). Almost all band recoveries have occurred on the South Farallon Islands (e.g., Sydeman 1993) or on beaches in central California (U.S. Geological Survey, Bird Banding Laboratory, unpublished data). A broad picture of murre movements can be ascertained from at-sea surveys, colony attendance patterns, and observations of parent-chick pairs at sea from California to British Columbia. Hundreds of thousands of murres are present along the outer coast of Washington and southern British Columbia between the Straits of Juan de Fuca and Clayoquot Sound in July-September (Manuwal 1981; Wahl et al. 1981; Speichetal. 1987; Vermeer etal. 1987, 1992; Campbell et al. 1990; Morgan et al. 1 99 1 ; Thompson 1997; H. R. Carter and S. G. Sealy, unpublished data). These large numbers exceed estimates of breeding population sizes in Washington and British Columbia (Carter et al. 200 1 ). Thus, it is clear that a substantial northward movement of Oregon murres (700,000 breeding birds) occurs into this area, as also indicated with the limited banding data noted above. In Barkley Sound, British Columbia, parent-chick groups and other murres arrived in large numbers in July 1979 and 1980, at least a month before chicks depart from the Triangle Island and Cleland Island colonies farther north along the west coast of Vancouver Island (H. R. Carter and S. G. Sealy, unpublished data). Thus, most birds likely originated from Oregon where departure from colonies usually occurs between late June and late July, earlier than at Washington colonies (see above). Small chicks recorded in Barkley Sound in late August and September probably originated from British Columbia or Washington colonies. Some adult-chick pairs from Triangle Island also move into Queen Charlotte Strait. On 2 September 1999, a concentration of 390 common murres and 130 rhinoceros auklets was observed off the Murray Labyrinth, in the south mouth of Schooner Channel, on the eastern side of Queen Charlotte Strait (G. W. Kaiser, personal communication). Unlike smaller groups farther at sea, these birds were flightless and included many chicks noticeably smaller than adults. From October to March, large numbers remain in northern Washington and southern British Columbia, although local movements occur within this area (see above). No evidence exists of a major movement of murres from Alaska into southern British Columbia or northern Washington between July and September, when murres are rearing chicks and undergoing the flightless prebasic molt in Alaska, or from October to March, when murres BIOLOGY AND CONSERVATION OF THE COMMON MURRE 21 are present in high numbers in southern Alaska (e.g., Forsell and Gould 1981: Gould et al. 1982). Breeding murres in California are resident and remain near colonies throughout the year as evidenced by ( 1 ) high at-sea densities near colony areas throughout the year (see earlier); (2) extensive winter attendance of monitored plots in breeding areas at the South Farallon Islands (Boekelheide et al. 1990; Sydeman et al. 1997; Hastings et al. 1998); (3) winter attendance at many other colonies in central and northern California (Ainley 1976; DeGange and Sowls 1981; Parker et al. 1997, 1998; Carter et al. 2001); and (4) at-sea chick rearing and prebasic molt occurring near colony areas (Stenzel et al. 1988; Boekelheide et al. 1990; Croll 1990; Carter 1 9%). Year-round residency of common murres has been demonstrated with banded birds in the Baltic Sea (Olsson et al. 2000). However, some northward movement of murres from northern California may occur after colony departure or after completion of prebasic molt. At-sea densities, total population estimates, and distribution of murres in California in winter are largely consistent with sunmier numbers if adjusted for colony attendance, populations of subadult murres, changes in local at-sea distribution, and survey error. In fact, the overall mean density for northern and central California combined in July (5.14 ± 12.52 birds per km-) was higher than in December (3.54 ±7.71 birds per km^ Tyler et al. 1993). Limited banding data support little or no movement of murres away from central California (see above). Higher winter at-sea numbers in northern California after December may indicate some limited movement of murres from Oregon in January and February in certain years, although colony attendance, populations of subadult murres, changes in at-sea distribution, and survey error also may be involved (Briggs et al. 1983, 1987; Tyler et al. 1993). Such movement may occur as Oregon murres move south and return to colony areas but before regular attendance at colonies. However, if substantial northward movement of northern California murres occurs in early fall, higher numbers in December may simply reflect return of northern California murres. Smail et al. ( 1972) considered that some northern murres (U. a. inomata) were killed in the 1971 San Francisco oil spill; this conclusion was based on morphometric comparisons using data in Storer (1952) but there is now doubt over their approach (Warheit 1995). Movements of large numbers of murres to central California from other populations between December and April are not confirmed with existing data. However, small numbers of common murres from Alaska {U. a. inomata) may be present from southern British Columbia to California in winter. For instance, small numbers of thick-bUled murres have been noted far south of major colonies in Alaska in certain years (e.g., Scott and Nehls 1974; Roberson 1985). In southern California, moderate numbers of murres are present in fall and winter and small numbers during summer (Briggs et al. 1983, 1987; Lehman 1994; Carter et al. 2001 ), presumably from central California colonies. Male-chick groups have been noted in July as far south as northern Santa Barbara County in some years (Lehman 1994). Murres are most common in Santa Barbara and San Luis Obispo Counties from July to January (Briggs et al. 1983, 1987). R. Rowlett (unpublished data), however, recorded 2,030 murres between 5 and 1 2 May 1996 off Point Piedras Blancas. Smaller numbers occur south to San Diego County and northern Baja California mainly in November-January, with stragglers as late as June (Unitt 1984; Howell and Webb 1995). In late summer and early fall (August to October), conmion murres from Triangle Island. British Columbia, probably move south to the northwest or northeast coasts of Vancouver Island. Small numbers of parent- chick pairs observed in Kyuquot Sound and Checleset Bay on northwestern Vancouver Island may originate from Triangle Island or Oregon and Washington colonies, depending on observation date (Guiguet 1972; Campbell et al. 1990). By late fall and winter, these murres may stay in northern Vancouver Island waters or move south and join large numbers in the Straits of Juan de Fuca, Strait of Georgia, Puget Sound, or southwest Vancouver Island. Higher numbers of murres in Hecate Strait and Dixon Entrance in spring and fall likely indicate southward movement of some Alaskan birds, especially from the isolated Forrester Island colony located just north of Dixon Entrance in southeast Alaska (Sowls etal. 1978;Vermeeretal. 1983; Campbell et al. 1990, Morgan et al. 1991 ; Carter et al. 2001). In early October 1986 and 1997, several adult- chick pairs were observed in Skidegate Inlet on the east coast of the Queen Charlotte Islands (S. G. Sealy, personal communication). Other winter movements probably occur, especially by some younger subadults which are known to travel more widely in winter than adults in Europe (e.g., Birkhead 1974; Mead 1974; Olsson et al. 2000). Two murres banded at the South Farallon Islands have been recovered off the Washington and Oregon coasts (U.S. Geological Survey, Bird Banding Laboratory, unpublished data). Three birds banded in Oregon were recovered in central California (Storer 1952; Tuck 1961 ; Bayer and Ferris 1987). 22 USGS/BRD/ITR-2000-0012 Acknowledgments This chapter has benefitted greatly from detailed reviews and editorial comments of various drafts, or portions thereof, by D. G. Ainley, D. Bertram, G. V. Byrd, A. J. Gaston, M. P. Harris, K. Kilbride, R. W. Lowe, G. J. McChesney, D. N. Nettleship, S. Olson-Edge, M. W. Parker, F. L. Paveglio, M. S. Rodway, S. G. Sealy, W. J. Sydeman, J. E. Takekawa, J. L. Trapp, U. W. Wilson, J. L. Yee, and T. S. Zimmerman. Administrative support was provided by T. S. Zimmerman, B. Bortner, and D. L. Orthmeyer. J. L. Yee helped prepare Figures 1 .5 and 1 .7. Unpublished data were provided by G. W. Kaiser, R. W. Lowe, M. W. Parker, S. G. Sealy, and W. J. Sydeman. Studies of the common murre in Barkley Sound, British Columbia, in 1979-80 were funded by grants from the Natural Sciences and Engineering Research Council of Canada to S. G. Sealy and Canadian Wildlife Service Scholarships to H. R. Carter. Photographs were provided by R. W. Lowe, M. W. Parker, and M. S. Rodway. Studies at the South Farallon Islands (Farallon National Wildlife Refuge) are a valuable part of the knowledge of murres in California, Oregon, Washington, and British Columbia. Since 1971, the.se studies have been conducted through a cooperative program between the Point Reyes Bird Observatory (Stinson Beach, California) and USFWS (San Francisco Bay National Wildlife Refuge Complex, Fremont, California). The Point Reyes Bird Observatory has staffed the islands year-round with a series of biologists over the years (including H. R. Carter from 1983 to 1986) who collect monitoring and research data on seabirds, marine mammals, and other aspects of island ecology. The program has been supported partly by private and research funding obtained through the efforts of Point Reyes Bird Observatory Marine Program Directors D. G. Ainley ( 1 97 1-92) and W. J. Sydeman ( 1 993-present), with administrative support from Point Reyes Bird Observatory Executive Directors D. Evans, B. Heneman, L. Waybum, and others. 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Pacific Biological Station, Nanaimo, British Columbia. Robertson, I. 1 974. An inventory of seabirds occurring along the west coast of Canada. Part II: The 32 USGS/BRD/ITR-2000-0012 shoreline and inlet zone. Unpublished report, Canadian Wildlife Service, Pacific and Yukon Region, Delta, British Columbia. Speich, S. M., B. L. Troutman, A. C. Geiger, P. J. Meehan- Martin, and S. J. Jeffries. 1987. Evaluation of military flight operations on wildlife of the Copalis National Wildlife Refuge, 1984-1985. Unpublished final report, U.S. Navy, Western Division, Naval Facilities Engineering Command, San Bruno, California. Stenzel, L. E., G. W. Page, H. R. Carter, and D. G. Ainley. 1988. Seabird mortality in California as witnessed through 14 years of beached bird censuses. Unpublished report. Point Reyes Bird Observatory, Stinson Beach, California. Sydeman, W. J., H. R. Carter, J. E. Takekawa, and N. Nur. 1997. Common murre (Uria aalge) population trends at the South Farallon Islands, California, 1985-1995. Unpublished report. Point Reyes Bird Observatory, Stinson Beach, California, U.S. Geological Survey, Dixon, California, and U.S. Fish and Wildlife Service, Newark, California. Sydeman, W. J., J. A. Thayer, M. M. Hester and N. P. Fairman. 1998. Colony formation and nest site selection of common murres on Southeast Farallon Island, California. Unpublished report. Point Reyes Bird Observatory, Stinson Beach, California. Thompson, C. W. 1997. Distribution and abundance of marbled murrelets and common murres on the outer coast of Washington. Unpublished report, Washington Department of Fish and Wildlife, Olympia. Washington. Vallee, A. J., and H. R. Carter. 1987. Breeding phenology of common murres on Triangle Island, British Columbia, in 1 980 and 1 98 1 . Pacific Seabird Group Bulletin 14:71. Varoujean, D. H., S. D. Sanders, M. R. Graybill, and L. Spear. 1979. Aspects of common murre breeding biology. Pacific Seabird Group Bulletin 6:28 (abstract). Warheit, K. L. 1995. Assessment of the origin of and the demographic impact to common murres {Uria aalge) killed during the 1991 Tenyo Maru oil spill. Unpublished report, Washington Department of Fish and Wildlife, Olympia, Washington. Warheit, K. L. 1997. Common murre {Uria aalge). In E.M. Larson, editor Management recommendations for Washington's priority species. Volume 4: Birds. Washington Department of Wildlife, Olympia. Wilson, M. L., and C. W. Thompson. 1998. Dietary preferences of common murres and rhinoceros auklets in Puget Sound, Washington in late summer and fall 1993-1996. Pacific Seabirds 25:48-49 (abstract). Unpublished data and personal communications Ford, R. Glenn, R. G. Ford Consulting, 2735 N. E. Weidler Street, Portland, Oregon 97232 Kaiser, Gary W., Canadian Wildlife Service, Pacific Wildlife Research Centre, Rural Route 1, 5421 Robertson Road, Delta, British Columbia V4K 3N2 Canada Lowe, Roy W., U.S. Fish and Wildlife Service, Oregon Coast National Wildlife Refuge Complex, 2127 S. E. OSU Drive, Newport, Oregon 97365 Parker, Michael W., U.S. Fish and Wildlife Service, San Francisco Bay National Wildlife Refuge, P.O. Box 524, Newark, California 94560 Rowlett, Richard A., P. O. Box 7386, Bellevue, Washington 98008 Sealy, Spencer G., Department of Zoology, University of Manitoba, Winnipeg, Manitoba R3T 2N2 Canada Spear, Larry B., H. T. Harvey and Associates, 3150 Almaden Expressway, San Jose, California 951 18 Sydeman, William J., Point Reyes Bird Observatory, 4990 Shoreline Highway, Stinson Beach, California 94970 U. S. Geological Survey, Bird Banding Laboratory, 12100 Beech Forest Road, Suite 4037, Laurel, Maryland 20708 Wilson, Ulrich W., U.S. Fish and Wildlife Service, Washington Maritime National Wildlife Refuge Complex, 33 South Barr Road, Port Angeles, Washington 98362 Chapter 2 Population Trends of the Common Murre (Uria aalge californica) by Harry R. Carter", Ulrich W. Wilson^ Roy W. Lx)we\ Michael S. Rodwa/, David A. ManuwaP, Jean E. Takekawa*, and Julie L. Yee^ 'Humboldt Slate University, Department of Wildlife Areata, California 95521 'U.S. Fish and Midlife Service. Washington Maritime National Wildlife Refuge Complex 33 South Barr Road Port Angeles. Washington 98362 ^U.S. Fish and Wildlife Service, Oregon Coast National Wildlife Refuge Complex 2127 S.E. OSU Drive Newport. Oregon 97365 *Simon Fraser University. Department of Biological Sciences Bumaby, British Columbia V5A 1S6 'University of Washington, College of Forest Resources Wildlife Science Group Seattle. Washington 98195 ''U.S. Fish and Wildlife Service, Nisqually National Wildlife Refuge 100 Brown Farm Road Olympia, Washington 98516 ^U.S. Geological Survey. Western Ecological Research Center Dixon Field Station, 6924 Tremont Road Dixon, California 95620 Abstract: Population trends for the common murre (Uria aalge californica) were determined from available whole-colony counts of murres in California, Oregon. Washington, and British Columbia from 1 800 to 1 995. From 1800 to 1978, historical counts were sporadic and not standardized. From 1979 to 1995, standardized whole-colony counts from aerial photographs were conducted in many years in California, Oregon, and Washington. In contrast, no aerial photographs of murre colonies in British Columbia have been taken and only a few other whole-colony counts have been conducted. Direct comparisons and statistical treatment of Suggested Citation: Carter. H. R.. U. W. Wilson, R. W. Lowe, M. S. Rodway, D. A. Manuwal, J. E. Takekawa, and J. L. Yee. 200 1 . Population trends of the common murre (Uria aalge californica). Pages 33-132 in D. A. Manuwal, H. R. Carter, T. S. Zimmerman, and D. L. Orthmeyer. editors. Biology and conservation of the common murre in California, Oregon. Washington, and British Columbia. Volume 1: Natural history and population trends. U.S. Geological Survey, Information and Technology Report USGS/BRD/ITR- 2000-0012. Washington, D.C. 34 USGS/BRD/ITR-2000-0012 whole-colony counts were conducted using 1979-95 data. Complete data for all colonies were available only in 1988-89 when the breeding murre population was estimated to be 1.1 million, about 5-8% of the world population and 13-28% of the Pacific Ocean population. A summary of various natural and anthropogenic factors affecting murre populations in western North America since 1 800, and particularly in 1 979-95, also is provided. A relatively good history exists for murre colonies in central California. The well-known colony at the South Farallon Islands may have numbered 1-3 million birds in the early 1 800s. Egging and human disturbance throughout most of the nineteenth century, plus mortality from oil pollution in the early twentieth century, caused the near extirpation of this colony by the 1 930s. Since the 1 950s. this colony has grown and, by the early 1980s, again was the largest colony in central California. Two other large colonies also are present in central California at the North Farallon Islands and Point Reyes. In the early twentieth century. Prince Island in southern California was the southernmost breeding colony of U. a. califomica, but the colony was extirpated in about 1912. Hurricane Point Rocks in central California is now the southernmost colony. In 1 980-82, the central California breeding population was estimated at 1 94,000-224,000 breeding birds at nine active colonies. From 1979 to 1989, this population declined 9.9% per annum (P = 0.002) because of mortality from gill nets and oil spills, in concert with detrimental effects from the severe 1982-83 El Nifio. All colonies declined significantly and the Devil's Slide Rock colony was extirpated. In 1 989, the population was estimated at 90,200 breeding birds at 8 active colonies (i.e., 8% of the U. a. califomica population). From 1985 to 1995, the population increased 5.9% per annum (P = 0.002), mostly since 1989-90, but had only partly recovered to 1979-82 levels by 1995. Increase since the late 1980s has occurred despite continuing anthropogenic impacts and low reproduction during the severe 1992-93 El Nino. The Devil's Slide Rock colony did not recover between 1986 and 1995, but breeding has been restored in 1996-2000, using social attraction techniques. In northern California, limited historical data indicated that murre colonies were heavily affected by early settlers in the late nineteenth century, as well as oil pollution in the early twentieth century. Only two colonies (i.e.. Castle and Green Rocks) were specifically known prior to the late 1 940s. Detrimental effects apparently lessened in the mid-twentieth century, allowing substantial population growth over several decades since the 1 930s, including many recolonization events prior to the 1 970s. Little change in available population numbers occurred from 1979 to 1989, which suggests a possible leveling of population numbers and little or no long-term detrimental effects from the 1982-83 El Niiio. Lower numbers at Castle Rock in 1986 and 1989 appear related to differences in survey techniques. In 1989, the breeding population was estimated at about 261,400 breeding birds at 1 1 active colonies (i.e., 24% of the U. a. califomica population). The largest colonies were at Castle Rock, False Klamath Rock, Green Rock, Flatiron Rock, and False Cape Rocks. Colonies had lower numbers in 1993 indicating short-term abandonment during the severe 1992-93 El Nino, but with few long-term detrimental effects. Recolonization and population increase have continued since the 1970s at the southern end of this population. The vast majority of murres in western North America, south of Alaska, now breed in Oregon. Numbers of murres in the nineteenth and early twentieth centuries were much lower owing to extensive use of coastal rocks and islands by native peoples, followed by egging and human disturbance by early settlers. However, the population increased for several decades in mid-twentieth century. By 1 988, about 7 1 1 ,900 breeding birds were estimated at 66 active colonies (i.e., 66% of the U. a. califomica population). The largest colonies were at Shag Rock, Finley Rock, Middle Rock, Gull Rock (Cape Blanco). 270-1 10, Cat and Kittens, and 219-018. A sample of 15 colony sites indicated that murre numbers changed little from 1988 to 1995, except for short-term abandonment during the severe 1992-93 El Niiio. Long-term detrimental effects from severe El Niiios in 1982-83 or 1992-93 have not been detected. Historical accounts indicate that murre populations in Washington increased from 1907 to 1979. In 1979, about 53,000 breeding birds were estimated at 18 active colonies. The largest colonies were at Split Rock, Willoughby Rock, Grenville Arch, and Rounded Island. Between 1979 and 1986, a 43.7% per annum {P = 0.006) decline occurred in the number of murres attending breeding colonies in southern Washington. Overall numbers of murres in Washington declined 13.3% per annum (P = 0.003) from 1979 to 1995. By 1988, about 7,000 breeding birds (i.e.. less than 1% of the U. a. califomica population) remained. Declines apparently were related to the 1981 warm water event, the 1982-83 El Nifio, and anthropogenic factors (i.e., human disturbance at colonies and gillnet and oil-spill related deaths). No recovery occurred in southern Washington from 1984 to 1995 but limited increase in the number of murres attending some colonies in northern Washington was documented. Increase at Tatoosh Island from 1984 to 1995 involved intercolony movements and intrinsic growth. The Washington murre population size has recovered little since its decline in the early 1980s, and remained low through 1995. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 35 Small numbers of murres breed in British Columbia and there is no evidence to suggest they are more numerous than in 1900. About 8,300 breeding birds (i.e., less than 1% of the U. a. califomica population) were estimated at two active colonies in 1989, although five other small colonies had been active in the 1970s. The northernmost colony of U. a. califomica is at the Kerouard Islands at the southern tip of the Queen Charlotte Islands. In British Columbia, the vast majority of murres breed at the large colony at Triangle Island off the northern tip of Vancouver Island. Population trends at Triangle Island have not been well assessed. Key words: Alcidae, breeding colony, breeding distribution, British Columbia, California, colony disturbance, colony extirpation, colony formation, common murre, egging. El Niiio. gill net. habitat change, oil spill, Oregon, population size, population trends, predators, seabird, Uria aalge, Washington Information on populations of the common murre {Uria aalge califomica) in California, Oregon, Washington, and British Columbia are of two types, whole-colony counts of birds, which can be adjusted to derive estimates of the number of breeding adults at each colony, and transect counts of birds at sea, which describe at-sea densities. These two types of population data serve as primary baseline information for monitoring and assessing trends in populations of murres in various geographic areas in western North America (Sowls et al. 1980: Briggs et al. 1987, 1992: Speich and Wahl 1989: Takekawa et al. 1990: Rodway 1991: Wilson 1991: Carter et al. 1992, 1995: Byrd et al. 1993; Tyler et al. 1993). Standardized whole-colony counts include a large proportion of breeding birds (i.e., each egg or chick had one or two attending adults) and some nonbreeding individuals attending the colony. Thus, whole-colony counts of all colonies in a geographic area constitute a primary population index wherein most of the population is counted directly rather than sampled. This kind of population index increases our ability to measure trends by greatly reducing potential variation or bias from sampling. At each colony, this index is related directly to the number of breeding adults or the total number of murres (breeding and nonbreeding) attending the colony, but the exact relation has not been determined. Estimates of the number of breeding birds at a colony can be derived from whole-colony counts with the use of a correction factor k (see Appendix A). Similarly, estimates of the numbers of nonbreeding birds can be derived through population modeling. However, k correction factors and demographic variables used in population models have been determined in only a few studies at certain locations and may not apply widely. We considered trends in sums of standardized whole-colony counts from aerial photographs for all or many colonies in a geographic area to best reflect trends in murre populations over time. Within the range of U. a. califomica, whole-colony counts can be conducted at all colonies, which reduces the potential for sampling error (e.g., if one colony were selected for monitoring in an area). Source colonies of birds also are known for colony counts but must be interpreted using various sources of information for at-sea counts. In general, standardized whole-colony counts are less variable, more repeatable, and subject to fewer biases than at-sea counts. However, numbers of murres attending colonies during the breeding season are subject to variation because of several factors, especially time of season, time of day, and colony disruption by human disturbance or interactions with other seabirds or marine mammals. Transect counts of birds at sea also can be extrapolated over large areas to derive estimates of total population (i.e., adults and subadults) in a defined geographic area, but must account for murres attending colonies. At-sea counts and total-population estimates provide important data on the density, distribution, abundance, and movements of murres at sea, which are important in connection with various conservation issues. Significantly more baseline population information useful for monitoring purposes is available for colonies than for at-sea murre distribution and abundance. Since 1979, monitoring of murres in California, Oregon, and Washington has focused primarily on standardized whole-colony counts from aerial photographs of birds attending colonies during the breeding season. The monitoring is so focused because (1) most colonies are comparatively small (fewer than 20,000 breeding birds) and are present on small islands with open habitats that can be aerially photographed on a regular basis, (2) intensive monitoring of plots within most colonies is impractical because most colonies are inaccessible or cannot be accessed without extensive disturbance to breeding birds, (3) potential biases are associated with monitoring plots from the ground (i.e., plot selections, number of plots, variation between plots, and counting error [Harris et al. 1986: Mudge 1988: Harris 1989]), and (4) monitoring plots can involve high cost and effort. The U.S. Fish and 36 USGS/BRD/ITR-2000-0012 Wildlife Service (USFWS) manages and surveys most murre colonies in Washington and Oregon, and important colonies in California, within the National Wildlife Refuge System. In California, however, most colonies are managed by the California Department of Fish and Game and tlie National Park Service, and surveys have been conducted by a combination of personnel from the USFWS, Humboldt State University, U.S. Geological Survey and University of California. Aerial photographic surveys can be conducted by refuge staff or other researchers at a reasonable cost in a short period of time during the breeding season, although the subsequent counting of photographs requires substantial effort. In certain other parts of the breeding range of the common murre, sample plots have been established as the primary method for monitoring where deriving accurate whole-colony counts from aerial photographs of entire colonies is either too difficult, too costly, or impossible. Overall, researchers have used a combination of survey and census techniques to monitor murre populations around the world, with techniques varying between colonies and geographic areas (Birkhead and Nettleship 1980; Gaston and Nettleship 1981). However, standardized or nonstandardized whole-colony counts at one or more colonies over several years have been used by many researchers to describe common murre population trends in various parts of the Atlantic and Pacific Oceans (Hudson 1985; Nettleship and Evans 1985; Vader et al. 1990; Byrd et al. 1993). Aerial photographic surveys of murre colonies at Funk Island, Newfoundland, and several colonies in eastern Canada have been employed since 1972 (D. N. Nettleship, personal communication). Whole-colony counts of murres provide the best available baseline information for analysis of trends in the number of murres attending colonies in California, Oregon, and Washington. Available data sets are hampered, however, by four main factors: (1) incomplete or irregular survey coverage (i.e., surveys not conducted in some years, certain colonies omitted in certain years), (2) incomplete colony coverage (i.e., poor quality or incomplete sets of photographs at certain colonies in certain years), (3) incomplete counting of available aerial photographs in northern California and Oregon, and (4) single counts in most years (i.e., variation in whole-colony counts has not been fully assessed). For central California, Oregon, and Washington, such problems were limited, have been reduced over the past decade, and did not greatly affect the use of whole-colony counts for assessing murre population trends. However, we have identified and accounted for serious problems in certain cases. In northern California and British Columbia, available information was much more limited for assessing recent trends than in other areas. Under unusual circumstances, whole-colony counts may not accurately reflect the actual colony size; for instance, during severe El Nifio-induced weather conditions, large numbers of murres may not attend colonies during annual surveys. Such circumstances must be identified and accounted for in assessments of population trends, using whole-colony count data. In Alaska, common murres often breed sympatrically with thick-billed murres {U. lomvia) and it is often difficult to determine the proportions of each species (Sowls et al. 1978). This problem does not exist throughout most of the geographic area of western North America covered in this chapter. The current southern limit of breeding thick-billed murres is at Triangle Island, British Columbia, where up to 70 thick-billed murres have been recorded attending the colony (Vallee and Cannings 1983; Rodway 1991). In this chapter, we have examined population trends of common murres using available information from whole-colony counts, primarily from aerial photographs, in California, Oregon, Washington, and British Columbia through 1995. In addition, we have reported estimates of the size of breeding populations of U. a. californica in different geographic areas. We have not attempted to collate information on at-sea densities or total-population estimates, but aspects of at-sea distribution, abundance, and movements are summarized in Manuwal and Carter (2001). Methods We used a broad framework for assessing murre population trends within six geographic areas along the west coast of North America: central California, northern California, Oregon, southern Washington, northern Washington, and British Columbia. Information provided for each area includes summaries of (1) qualitative and nonstandardized quantitative historical data from 1800 to 1978 of numbers of murres attending colonies and known or suspected human activities at colonies, (2) current breeding population size and distribution of colonies, and (3) major population changes identified between 1 979 and 1 995 (using standardized whole-colony count methods) and factors known or suspected to be associated with changes observed. Significant events documented after 1995 were noted where appropriate but data used for population trend analysis were restricted to the 1979- 95 period. Historical information on murres at colonies helped to derive a general concept of long-term colony and BIOLOGY AND CONSERVATION OF THE COMMON MURRE 37 regional population trends prior to 1979. To summarize historical information, and without the aid of computerized databases or search processes, we consulted all available published and unpublished sources known to us from prior research as follows: California (H. R. Carter, see Appendix B). Oregon (R. W. Lowe), Washington (U. W. Wilson and H. R. Carter), and British Columbia (M. S. Rodway and H. R. Carter). To augment historical information. H. R. Carter also examined egg records in California, Oregon. Washington, and British Columbia in major museum collections, including Western Foundation of Vertebrate Zoology. Camarillo. California (WFVZ); Humboldt State University. Department of Wildlife Museum. Areata. California (HSUWM): Santa Barbara Natural History Museum. Santa Barbara. California (SBNHM): San Diego Namral History Museum. San Diego. California (SDNHM): University of California Berkeley. Museum of Vertebrate Zoology. Berkeley. California (BMVZ); National Museum of Natural History. Smithsonian Institution. Washington. D.C. (USNM); Museum of Comparative 2^1ogy, Har\'ard University. Cambridge. Massachusetts (MCZ); Royal British Columbia Museum. Victoria. British Columbia (RBCM); and University of British Columbia Zoology Museum, Vancouver. British Columbia (UBCZM). Substantial historical information was rediscovered in these museum collections. Annual survey data for each colony in 1979-95 were collated as follows: California (H. R. Carter and J. E. Takekawa; see Appendices C, D), Oregon (R. W. Lowe; see Appendix E), Washington (U. W. Wilson; see Appendixes F and G), and British Columbia (M. S. Rodway). Regional estimates of the total number of murres attending colonies during surveys were determined by summing single representative whole- colony counts firom aerial photographic surveys for each colony within a particular year in central and northern California and southern and northern Washington (see Appendix A for survey methods and summary ). For these areas, we summed counts only when all or most colonies were judged to have been surveyed in a generally standardized and compatible fashion in the same year. For Oregon, we summed counts for 15 sample colonies that were surveyed and counted atuiually between 1988 and 1995. This sample of colonies is spread along the entire Oregon coast, but several large colonies are not included because of extensive counting time required. Annual sums of whole-colony counts in each geographic area are presented in Appendix H. In keeping with seabird colony catalogs (Sowls et al. 1980; Speich and Wahl 1989: Rodway 1 991; Carter etal. 1992), we referred to specific colonies or subcolonies as they have been previously defined, which allowed easy cross referencing between sources. We also summed whole-colony counts within "colony complexes" in California and Washington. We considered a colony complex to be a geographic subunit, composed of several colonies close together. Such subunits reflected major geographic assemblages of breeding murres that resulted from the distribution of suitable breeding habitat, accounted for the greater potential for interaction between nearby colonies, and accounted for inconsistent definitions of what constituted a colony in seabird colony catalogs (Sowls et al. 1980; Speich and Wahl 1989; Carter et al. 1992). We lumped adjacent rocks, islands or mainland cliffs with groups of breeding murres into colony complexes when they were within about 5 km of each other. Colony complex totals are presented in Appendix H. Regression analysis has been used extensively to assess avian population trends and is a widely accepted method of demonstrating and measuring the rate of population change over a period of time (Sauer and Droege 1990). We used regression analysis to calculate rates of population change (percent per aimum change with 95% confidence inter\als) for each area within certain periods and to determine statistical significance for population trends identified in these periods (see Appendix H). We conducted linear regression analyses on single, annual sums of whole-colony counts in geographic areas over a period of years, only including standardized and compatible data. Because of availability of data and previously identified population changes, we conducted regressions over all years of available data between 1979 and 1995, as well as on series of years where our direct inspection of data indicated a distinct trend (i.e., increasing, decreasing, or no change). This approach led to the following regression periods: central California (1979-89. 1985- 95. 1979-95), northern California (1979-89), Oregon (1988-95), and Washington (1979-86. 1984-95. and 1979-95). Significant regressions (P < 0.050) are reported in the text and presented in figures. Where significant trends were not detected, changes in whole-colony counts are discussed in the text and presented in figures. For certain objectives, we estimated the number of breeding adults at a colony and summed colonies to determine the size of a breeding population. Whole-colony counts of murres can be adjusted with a k correction factor to convert whole-colony counts to either "number of breeding pairs" or "number of breeding individuals" (Nettleship 1976; Birkhead and Nettleship 1980; Sowls et al. 1980; Takekawa et al. 38 USGS/BRD/ITR-2000-0012 1990; Carter et al. 1992; Sydeman et al. 1997). We applied a k correction factor to estimate the number of breeding individuals. Sydeman et al. ( 1997) calculated k from data collected between 1985 and 1995 at the South Farallon Islands in central California. An average k of 1.671 (SE = 0.026; n= 11) was obtained with relatively little variation among years (.see Appendix A). A k was not determined for any colony in northern California. Oregon, or Washington. A very different k was found for Triangle Island in British Columbia (see Appendix A). For all estimates of the number of breeding murres in California, Oregon, and Washington, we used a constant k correction factor of 1 .67. This approach allowed rough estimation of population sizes for general comparisons. However, given concerns about potential variation in k correction factors between different parts of the breeding range, season, times of day, and years, we did not apply a k correction factor to whole-colony count data before examining population trends. Summary of Population Data California Historical Background on Breeding Colonies in California, 1800-1978 The history of the common murre on the west coast of North America before I9(X) is best documented in California. Settlement of southern and central California by the Spanish began in the eighteenth century, much earlier than European colonization farther north along the west coast of North America south of Alaska. Frequent activity by eariy settlers probably occurred at many colonies, mainly from the mid-nineteenth thanigh the early twentieth centuries when rapid immigration occurred after California was ceded to the United States by Mexico in 1 848. Except at the South Fiu~allon Islands, little dcKumentation is available. In northern California, native people may have occasionally visited certain murre colonies by canoe to obtain eggs or birds until the late nineteenth century when populations of native people were reduced to very low levels. Whereas diets of native people in northern California did not focus on seabirds, they did feed extensively on marine foods, which probably included .seabirds on occasion (Heizer and Elsasser 1980). Such fcxxl gathering and hunting activities were limited to accessible offshore rcx-ky stacks and islets. In central California, visitation of murre colonies by native people probably was infrequent because they did not use large ocean-going canoes in this coastal area. Native people were not known to visit the South Farallon Islands, which are kvated far from shore. Below, we present a brief synopsis of the known history of murre colonies in California, and we refer the reader to Appendix B for a detailed account with citation to historical literature. Given extensive historical changes in California murre populations, current population status and trends of murres must be viewed with these earlier events in mind. At the South Farallon Islands, the harvest of murres and their eggs and the human occupation of the islands for nearly two centuries have greatly impacted the murre population. In 1818, the Russian sealing station on the South Farallon Islands (operated from 1812 to 1838) reported killing birds (probably murres) for meat and feathers. Egging was first reported in 1827. Commereial egging began in 1849, was made illegal in 1881, but continued until at least 1904. From 1850 to 1892, between 1 80,000 and 600,000 eggs were harvested annually, before falling to about 90,0(X) in 1896. Ainley and Lewis (1974) estimated that 400,000 birds may have bred at the South Farallon Islands, based on their review of egging records. However, our reinterpretation of historical records suggests numbers of murres were probably much higher, possibly between I and 3 million breeding birds (Appendix B). Hunting, egging, human occupation, and disturbance of these small islands, as well as heavy oil pollution, led to a dramatic decrease in the size of the murre colony at the South Farallon Islands. In 1909, the North Farallon Islands were included in the Farallon Re.servalion for Protection of Native Birds (later the Farallon National Wildlife Refuge). By 1911, there were fewer than 20,(XX) murres and very small numbers were reported in 1923. 1930, and 1933. Several thousands of murres died in the 1937 Frank Buck oil spill at the Golden Gate (Aldrich 1938; Moffit and Orr 1938). In the 1950s and 1960s, murre numbers at the South Farallon Islands grew and 6,7 1 8 were counted in 1959. In l%9, the South Farallon Islands were added to the Farallon National \\ ildlife Refuge. Additional protection from human disturbance was provided when the California Department of Fish and Game prohibited low overflights (although some still occurred) over the Farallon Islands Game Refuge in 1971. A detailed ground survey in 1972 revealed about 20.000-45.000 birds and the colony continued to increase to about 30.000-60.000 from 1975 to 1979, Estimates of population size varied widely owing to differences in census techniques, the degree of completeness of surveys, and irregular use of it correction factors. The increase between 1950 and 1982 reflects high levels of breeding success, reduction in human disturbance at the islands (especially since the early 1970s), and low levels of anthropogenic-related deaths at sea except for the 197 1 San Franci.sco oil spill when many thousands died (Small et al. 1972; Carter 1986; Boekelheide et al. 1990). BIOLOGY AND CONSERVATION OF THE COMMON MURRE 39 Few other islands in central and northern California were large enough for occupation by settlers (see Appendix I), but many colonies were accessible to people with small boats. Several colonies may have been extirpated during this period by egging and other activities. However, only the loss of colonies at Prince Island (c. 1912) and San Pedro Rock (c. 1908) are well documented. Egging was documented at other colonies, including the North Farallon Islands in the 1880s and 1890s. Point Reyes in 1897. and possibly Mendocino County in 1 900. Egging probably occurred at colonies near settlements at Trinidad and Crescent City. In addition to egging, extensive disturbance and human access resulting from construction and operation of the Ocean Shore Railroad may have contributed to the loss of the San Pedro Rock colony. Similarly, egg gathering for private collections may have contributed to the loss of the Prince Island colony, the only location in southern California where murre eggs were known to be collected between 1885 and 1912. Extensive oil pollution in the early twentieth century probably affected all colonies in central California. Colonies in northern California also may have been affected by oil pollution, judging by observations of oiled murres on beaches in 1909-10 (C. I. Clay, unpublished field notes). Other murre colonies may have been extirpated by eggers or others before documentation in the Channel Islands and throughout the coasts of San Luis Obispo, Monterey, Sonoma and Mendocino Counties where appropriate breeding habitats exist. Murres were rarely seen in southern California before the 1960s until populations in central California began to increase, with some murres moving south after breeding (Pyle 1953; Unitt 1984; Lehmann 1994; Manuwal and Carter 2001). The murre population in northern California seems to have increased markedly from the 1940s to the late 1970s following earlier decreases that resulted from activities of early settlers and use of certain islands by native people. A small colony was reported at Castle Rock between 1917 and 1935, but the population increased to 5,000-10.000 breeding pairs in 1956-61 and to 20,000-40,000 breeding pairs in 1970. In 1980, Castle Rock was included in the National Wildlife Refuge System. Increases at Castle Rock in the mid-twentieth century appear to reflect growth and recovery following use by native peoples, egging, and the use of the island for grazing by domestic animals. At Whaler Island, near Crescent City, breeding was documented in 1928. Since 1939. the island was partly quarried and a breakwater has connected it to the mainland allowing easy access by rats and humans, which has prevented breeding by most seabirds. Murres did not breed at Flatiron Rock from 1910 to 1934, but 1,000 breeding pairs were noted in 1969 and many thousands currently breed there. This colony is close to the long-settled port of Trinidad and would have been very accessible to commercial eggers by boat and native people by canoe (see Appendix I: Figure 1-15). In fact, large numbers of eggs were collected in 1897-1901 from several unidentified islands, apparently in the Trinidad area, indicating that higher population levels may have existed at that time. Nearby Green Rock seemed to be the only murre colony that existed in the Trinidad area from 1 9 1 7 to 1 94 1 . with about 2.000 birds noted in 1941 . By 1969-70, murres were found at most colonies where they have been recorded regularly since 1979 (except for Mendocino County), indicating population increase between the 1940s and late 1960s. Prior to the 1980s, certain California murre colonies outside of the Farallon and Castle Rock National Wildlife Refuges were protected within the Point Reyes National Seashore (i.e.. Point Reyes, Point Resistance, Millers Point Rocks, and Double Point Rocks), Redwood National Park (i.e.. False Klamath Rock and Sister Rocks), and Channel Islands National Park (i.e.. Prince Island) in 1%8, 1972, and 1980. respectively. Earlier. Prince Island had received partial protection when reserved for lighthouse purposes in 1 9 1 7 and transfenied to the U.S. Navy in 1934. Additional protection for murre colonies after 1980 in California are mentioned later in this chapter. Current Population Size and Distribution of Breeding Colonies in California By 1995. 26 murre colonies had been described in California, including 22 colonies used between 1979 and 1995 and 4 colonies extirpated earlier in the twentieth century (Appendixes B-D). The colonies separate into two groups: the northern California group consisting of 1 5 colonies in Del Norte. Humboldt, and northern Mendocino Counties (Figure 2.1); and the central California group consisting of 10 colonies in Marin, San Francisco. San Mateo, and Monterey Counties (Figure 2.2). One colony was previously reported in southern California (Santa Barbara County) at Prince Island, a record that represented the southern breeding limit known for the species in California and the world (Figure 2.2). Breeding has been confirmed with observations of eggs or chicks at all colonies in central California, the extirpated Prince Island colony in southern California, and most colonies in northern California (see Appendix B; Sowls et al, 1980. unpublished data archive; Boekelheide et al. 1990; Carter et al. 1992. unpublished data archive; McChesney et al. 1994; H. R. Carter, unpublished data; M. W. Parker, unpublished data; G. J. McChesney, 40 USGS/BRD/ITR-2000-0012 I RockR ' Sister Rocks False Klamath Rock Castle Rock \_ • Whaler Islan0_r Redding Rock • Sea Lion Rock White Rock Green Rock Flatiron Rock Blank Rock Pilot Rock False Cape Rock ■ Sugarloal Island Steamboat Rock ' Kibesillah Rock L Newport Rocks^ A Goat Island Area ■ Gualala Point Island 25 50 Kilometers in Rock attended wlo confirmed breeding Long-inactive colony Recently-inactive colony Recently-tormed colony Figure 2.1 . Distribution of common murre colonies in northem California (Del Norte to Sonoma Counties). personal observation). Murres breed regularly at the South Farallon Islands, Point Reyes, and Castle Rocks and Mainland colonies where long-term studies of murre biology and reproductive success are under way (see Chapter 1; Boekelheide et al. 1990; Parker et al. 1997, 1998, 1999; McChesney et al. 1998, 1999). The entire breeding population of murres in California was estimated in 1980, 1982, and 1989(Sowls et al. 1980; Briggs et al. 1983; Carter et al. 1992). On the basis of summed, whole-colony counts for all colonies, with a k correction factor, we calculated total populations of 467, 1 00, 5 1 4,900, and 35 1 ,600 breeding murres in 1980, 1982, and 1989, respectively. The central California population held 42, 43, and 26% of the total in each of the 3 years surveyed, respectively. The lower percentage in 1989 reflects extensive decline in central California from 1982 to 1989, and little change in northem California, except for lower revised estimates at Castle Rock (see later). In central California, colonies can be grouped into six colony complexes — two offshore complexes at the South and North Farallon Islands (about 20-30 km from the mainland) and four nearshore complexes (i.e., coastal rocks within 1 km of the mainland and adjacent mainland cliffs) at Point Reyes, Points Resistance-Double, Devil's Slide, and Castle-Hurricane (Figure 2.2; Appendixes C and D). The largest colony complex was the South Farallon Islands where an estimated 1 02,700 murres bred in 1982 (Table 2.1). Whole-colony counts at the South Farallon Islands averaged 38,019 birds per survey from 1979 to 1995, which corresponded to an estimated 63,500 breeding birds (Table 2.1). Two other large colony complexes were at the North Farallon Islands and Point Reyes, which averaged 34,600 and 23,000 breeding birds, respectively, during the same time period. Breeding on inaccessible mainland points occurs only at Point Reyes and Castle Rocks and Mainland. Three smaller colonies (Point Resistance, Millers Point Rocks, and Double Point Rocks) exist south of Point Reyes within the Points Resistance-Double complex. Colonies exist south of San Francisco at the Devil's Slide complex (including the Devil's Slide Rock and Mainland colony and the long-inactive colony at San Pedro Rock), as well as at the Castle-Hurricane complex (Figure 2.2). The southernmost colony in California in 1 979-95 was Hurricane Point Rocks. Point Reyes Pokit Rwistancs ~i Milters Point Rocks Double Point Rocks North Farallon Isiands- Soutti Farallon Islands • San Pedro Rock ~\ '^ Devil's Slide Rock S Mainland} * Martin's Beach k Bench Mark-227x Castie Rocks & Mainland Hurrkrane Point Rocks ' Rod( attended w/o con^rmed breeding > Long-inactive colony ' Recently-inactive colony ■ Recently-active colony 25 50 Kilometers San Miguel Island *" Santa RosaV3 C!!^!!!i£> Figure 2.2. Distribution of common murre colonies in central California (Marin to Monterey Counties) and southern California (Santa Barbara County). BIOLOGY AND CONSERVATION OF THE COMMON MURRE 41 Table 2.1 . Average and maximum sizes for nine breeding colonies of common murres in central California, 1 979-1 995 (see Appendixes C and D). Mean Mean number of Years Maximum Maximum number Year of Rank' Colony name counf breeding adults" of data count of breeding adults" maximum 1 South Farallon Islands 38,019 63,500 12 61,510 102.700 1982 2 North Farallon Islands 20,717 34,600 12 31,428 52,500 1980 3 Point Reyes 13,755 23,000 13 26,337 44,000 1982 4 Double Point 4,116 6,900 13 8,850 14,800 1980 5 Point Resistance 3,046 5,100 13 4,440 7,400 1980 6 Castle Rocks & Mainland 1,140 1,900 9 2,275 3,800 1980 7 Hurricane Point Rocks 692 1,200 10 1,500 2,500 1981 8 Devil's Slide Rock & Mainland" 446 700 11 1.750 2.900 1980 9 Miller's Point Rocks 256 400 9 713 1.200 1995 " Ranked in order of mean colony size. '' Only sites with at least five years of data considered suitable for trend analysis were included. Lower quality data for certain years and colonies were not included. " Number of breeding adults was obtained by multiplying mean or maximum count by a A: correction factor of 1 .67, and rounding to the nearest hundred. ■' No breeding occurred from 1986 to 1995 (see text). A new colony, "Bench Mark-227x," was 107,700 breeding birds in 1986 and 1989, respectively temporarily established within the Castle-Hurricane (Takekawa et al. 1990; Carter et al. 1992). Four other complex in 1996-98 but subsequent breeding did not large colony complexes are found at False Klamath, occur in 1999-2001 (Parker et al. 1998, 1999; Trinidad (including colonies at White Rock. Green McChesney et al. 1999; M. W. Parker, unpublished Rock. Hatiron Rock, Blank Rock, and Pilot Rock), Cape data). In March-June 1999, 3-9 murres attended but Mendocino (including False Cape Rocks and Steamboat did not breed at Prince Island, in association with Rockcolonies), and Vizcaino (including Cape Vizcaino nesting Brandt's cormorants (Phalacrocorax and Rockport Rocks colonies; Table 2.2). Mainland /7en/c/7/arM5;H. R.Carter, unpublished data). Use of the breeding occurs only at one subcolony on an Bench Mark-227x colony area had not been noted inaccessible point at Rockport Rocks. Smaller colonies previously, but murres had been recorded in the vicinity are present at Sister Rocks (within the False Klamath of Prince Island since 1991 (Carter et al. 1992; complex) and Redding Rock. By 1995. the McChesney et al. 1995). southernmost colony (where breeding was certain) in ^ ,.^ . , . ^ northern California was Cape Vizcaino. However, in In northern California, colonies are most often on ,nc.-, . j- <- j . .u n i • , . , . _ 1997. breeding was confirmed at three small colonies offshore rocks within 1 km of the mainland, except for ,^, _n i t^u n u r. i j/- .i i ja v „ . , , , „,,.„, i. . (Newport Rocks. Kibesillah Rock, and Goat Island Area) the small isolated colony at Redding Rock — 7 km .u ^ /^ \i- _u »« j • /^ _. , ~, , , south of Cape Vizcaino in northern Mendocino County offshore. The largest colony complex m northern , ... u aw .j- . /^/-_ . J. A A <-i where attendance had been noted in recent years (Carter et al. 1992, 1996; see below). California (and the state) in recent decades was at Castle Rock, where 142,400 breeding birds were estimated in 1982(Briggsetal. 1983;AppendixC). However, 1979- Between 1979 and 1995, murres attended several 82 counts may have overestimated the size of this dense rocks in California where breeding was not confirmed colony, which was estimated to be about 100,000 and (Sowlsetal. 1980, unpubHshed data; Briggsetal. 1983; Table 12. Average and maximum sizes for eight breeding colonies of common murres in northern California, 1 979-1 995 (see Appendixes C and D)=. Mean Mean number of Years of Maximum Maximum number Year of Rank Colony name count breeding adults data count of breeding adults maximum 1 False Klamath Rock 26,650 44.500 6 31,801 53,100 1982 2 Green Rock 24,327 40.600 6 32,934 55,000 1980 3 Flatiron Rock 16,799 28,100 8 25,494 42,600 1995 4 False Cape Rocks 8,847 14,800 7 12,426 20,800 1995 5 Cape Vizcaino 4,194 7,000 6 4.950 8,300 1995 6 Steamboat Rock 4,089 6.800 5 5.454 9,100 1989 7 White Rock 2,614 4,400 5 3.277 5,500 1981 8 Redding Rock 923 1,500 6 1.632 2,700 1989 The largest colony at Castle Rock was excluded (see text). Symbols and format as in Table 2. 1 42 USGS/BRD/ITR-2000-0012 Carter et al. 1992, 1996; Appendixes C and D). Near colonies in northern and central California, such attendance has been noted at Rock R, Sugarloaf Island, and Martin's Beach (Figures 2. 1 and 2.2; Appendixes C and D). In addition, such attendance was recorded south of known breeding areas in Mendocino and Sonoma Counties at Newport Rocks, Kibesillah Rock, Goat Island Area, White Rock, and Gualala Point Island (Figure 2.1; Appendixes C and D). Briggs et al. (1983) also noted murres on Bruhel Point Rocks (herein referred to as Newport Rocks). H. L. Cogswell (unpublished field notes) also noted at least 30 murres "resting on coastside rock in ocean below sea cliff at Pillar Point or Moss Beach on 27 November 1 952 and at least 6 murtes on "a small rocky islet offshore" of West Cliff Drive at Santa Cmz on 23 July 1967 (Figure 2.2). Carter et al. ( 1 992) classified attendance at Rock R and Goat Island Area in 1989 as newly-formed colonies without determining whether eggs were laid. Here, we reclassified these observations as "attendance without confirmed breeding." Breeding was ultimately verified at Kibesillah Rock, Newport Rocks, and Goat Island Area on 12-13 July 1997, when about 5-10 chicks and clumps of other birds in incubation or brooding postures were observed by telescope from the mainland (G. J. McChesney, personal observation). In retrospect, these colonies appearred to be forming during the 1989-95 period. Numbers of murres at Newport Rocks and adjacent Kibesillah Rock increased from 7 birds in 1 993 to 542 birds in 1 995 (Carter et al. 1 996). Similarly, small numbers of birds were noted at Goat Island Area in 1989, 1994, and 1995 and at Rock R in 1980, 1989, and 1994 (Sowlsetal. 1980; Carter etal. 1992, 1996). From 1989 to 1995, birds were present in clumps or rows, with some individuals in incubation postures (as seen in aerial photographs), which suggests possible breeding. In addition, one murre was observed carrying a fish (possibly to feed a chick or for courtship) in flight to the Goat Island Area in June 1989 (Carter et al. 1992; unpublished survey data). However, breeding probably was not occurring at Newport Rocks (1993-95) and Sister Rocks (1989-95), where all birds were standing and scattered during aerial photographic surveys. Population Trends in Central California, 1979-1995 From 1979 to 1982, overall numbers of murres attending colonies in central California increased (Figures 2.3 and 2.4; Appendix C; Sowls et al. 1980; Briggs et al. 1983). This increase was well documented, mainly at the largest colony at the South Farallon Islands where boat and ground surveys also documented the increase (Boekelheide et al. 1990; Takekawa et al. 1990; Sydeman et al. 1997). At the South Farallon Islands, the increase reflected part of a long-term increase that began in the 1950s (Appendix B; Carter 1986; Boekelheide et al. 1990; Sydeman et al. 1997). No increase occurred at the nearby North Farallon Islands during that time, possibly because of total occupation of more limited available breeding habitat (see Appendix I: Figure 1-9) and lower levels of past human disturbance compared to the South Farallon Islands. Counts at Point Reyes and the Points Resistance-Double complex varied, but also seemed to increase from 1979 to 1982. The effects of low overflights by aircraft (and possibly close approach by boats) may have contributed to this variation in numbers. However, the Gulf of the Farallones National Marine Sanctuary was created in 1981, which prohibited low overflights (below 1 ,000 feet or 305 m) over the colonies. McChesney et al . ( 1 998 ) also clarified that counts in 1979-81 at Point Reyes underestimated numbers of murres present because of incomplete and low-quality photographs. Taking this into account, little change was evident at Point Reyes between 1979 and 1982. Between 1980 and 1982, murte numbers were reduced at the Devil's Slide complex and decline was evident at the Castle-Hurricane complex. Between 1979 and 1989, all colony complexes in central California underwent large declines of 8.7 to 28.5% per annum, (0.001 < P < 0.020; Figure 2.3; Appendix H). The overall population declined 9.9% per annum {P = 0.002; Figure 2.4; Appendix H). Most decline occurred between 1982 and 1985, as further verified with ground-based observations at the South Farallon Islands (Boekelheide et al. 1990; Takekawa et al. 1990). Plot observations and ground and boat surveys at the South Farallon Islands showed low attendance and low breeding success during the severe El Niiio-related breeding conditions in 1983-84 (Boekelheide et al. 1990; Takekawa et al. 1990; Sydeman et al. 1997). Although no aerial photographs were taken in 1983-84, numbers at colonies in 1985 and 1986 after breeding conditions had returned to normal were still much lower than in 1981 and 1982 (Appendix C). By 1986, the Devil's Slide Rock and Mainland colony had essentially disappeared with between 0 and 128 murtes in 1986-87 and 0-5 murtes in 1988-95. Between 1987 and 1990, counts at most colonies reached their lowest levels compared to 1981-82 (Figure 2.3; Appendix D). The Castle-Hurricane complex reached the lowest level of all extant colony complexes (1,047 and 1,093 birds counted in 1988 and 1989, respectively) with loss of subcolonies and only small groups of birds on several remaining subcolonies. The small Millers Point Rocks colony (within the Points BIOLOGY AND CONSERVATION OF THE COMMON MURRE 43 PnnlRnvs PatoB ResKtaBcc - DsaMe i 1 im IIM un IIM IIM im l«M 1«*2 l«»4 l«M l«7« UM l*U MM l«H IMS l«M l««2 l«M IWt 3 E e e £ B a Z Nortk FaralloB Istaadt l*T( IM* l«SJ I4M IfM im ■«« l«*Z l*M l««t Swnk Firaloa idsMh DolTtSHdc Figure 2.3. Trends in whole-colony counts for six colony complexes of common murres in central California, 1 979-1 995 (see Appendix H). im MM INI I«t4 l«H l«n IM* IMI l««4 l*M Caidr - HwTicaac 1«7S IM* I«K I«*4 Um I«H in* I«*2 IW4 l«W I97S IW* I<«2 IW4 IfH I«SS I*M l«*l l<«4 I«M Year Central California Figure 2.4. Trends in wfiole-colony counts for common murres in central California, 1979-1995 (see Appendix H). E IM 140 120 100 80- 60- 40- 20 period r-square p-valoe 1979-1989 0.883 0.002 1985-1995 0.829 0.002 ~i i I 1 I 1 1 I i r 1978 1980 1982 1984 1986 1988 \e«r — I 1 1 — 1990 1992 1 ! 1 I 1994 1996 44 USGS/BRD/ITR-2000-0012 Resistance-Double complex) may have been nearly extirpated during this decline since only 23 birds were found in 1987. However, this colony grew to 380 birds by 1990, possibly because of intercolony movements from nearby colonies within this complex. However, a remarkable increase occurred at the South Farallon Islands between 1989 and 1990. In retrospect, this upswing signaled the end of the decline and the start of an increase for the central California population. Ground and boat surveys and plot counts from 1 989 to 1 995 at the South Farallon Islands also confirmed the end of decline by 1990 (Sydeman et al. 1997, 1998). The decline of the central California population between 1979 and 1989 and the loss of the Devil's Slide Rock and Mainland colony have been attributed mainly to extensive gill-net and oil-spill deaths, and reduced productivity related to the severe 1982-83 El Nifio (Carter 1986; Carter and Ainley 1987; Salzman 1989 Takekawa et al. 1990; Wild 1990; Piatt et al. 1991 Swartzman and Carter 1991; Carter et al. 1992, 1995 Ainley et al. 1994; Sydeman et al. 1997; McChesney et al. 1998, 1999). More than 75,000 murres died in 1979- 87 in central California as a result of gill-net fisheries (Takekawa et al. 1990). High mortality was attributed to the consistent spatial and temporal overlap of large numbers of feeding murres and high gill-net fishing effort in nearshore waters of Monterey Bay, Gulf of the Farallones, and Bodega Bay area from 1980-86. Most severe declines occurred at colonies located nearest areas of highest gill-net mortality. Two major oil spills occurred during this period and killed more than 8,000 murres. In November 1984, the Puerto Rican oil spill occurred off the Golden Gate, killing 1 ,500-2,000 murres (PRBO 1985; Ford et al. 1987). Mortality probably was focused on large colonies at the Farallon Islands and Point Reyes. In January-February 1986, the Apex Houston oil spill occurred between San Francisco and Monterey Bay, killing 6,300-7,500 murres (Page and Carter 1986; Ford etal. l987;Pageetal. 1990; Siskin etal. 1993). Mortality probably was spread more widely over all colonies with greatest impacts at Devil's Slide Rock and Mainland, Castle Rocks and Mainland, and Hurricane Point Rocks. The loss of the Devil's Slide Rock and Mainland colony (first noted in June 1986) was associated with this mortality, although earlier gill-net mortality had reduced the colony beforehand (Takekawa et al. 1990; Piatt et al. 1991; Swartzman and Carter 1991). Many smaller spills also killed thousands of murres between the late 1970s and 1989 (Stanzel et al. 1988; Carter 1997; Nur etal. 1997). Low productivity in the 1982-83 El Nino undoubtedly affected the ability of the central California population to recover in the late 1980s. However, it was not possible to detect whether or not increased deaths of adult or subadult murres resulted during severe El Niiio-induced winter weather conditions in 1982-83. At this time, high numbers of murres killed in gill nets were washing up on beaches but the cause of death for many nonoiled beached birds could not be determined (Stenzel et al. 1 988). A small part of the reported decline at certain colonies may have been related to (1) methodological differences between surveys in 1979- 82 and 1985-89, (2) undocumented human disturbances from low overflights and boats, or (3) depredation at colonies by peregrine falcons {Falco peregrinus) and common ravens (Corvus corax; Sydeman 1993; McChesney et al. 1998, 1999; M. W. Parker, unpublished data). The marked decline in the central California murre population between 1979 and 1989 far outweighed the relatively small increase by 1995 after this decline. Between 1985 and 1995, the total population increased 5.9% per annum (P = 0.002), whereas colony complexes increased between 4.6 and 7.2% per annum (0.001 iiiMeaMm<4ftais o Rock wiBiout bnetfng potsnlal SO Ktometers Willoughby Rock, and Carroll Island — still exist (Figure 2.9). Eggs or chicks were confirmed only at Willoughby Rock and Carroll Island (Dawson 1907; Jones 1909). One egg was collected by Dawson at Carroll Islet on 21 July 1906 from a colony of about 100 pairs with "most [eggs] hatched" (SBNHM egg records). Three eggs in the WFVZ collection were obtained on 20 June 1907 at "Birdrock," Washington (WFVZ No. 47,472- 47,474). Another egg collected on 12 June 1910 at Willoughby Island was from a colony of "500 pairs on south slope" (SBNHM egg records). No murres were observed at several other rocks subsequently attended by murres in historical literature: Erin's Bride, Split Rock, Destruction Island, North Rock. Rounded Islet, Giant's Graveyard, Quillayute Needles, Cake Rock, White Rock. Flattery Rocks (including Old Rock, also known as Bodelteh Islands). Point of the Arches (including Silversides), and Tatoosh Island. At Carroll Pillar (adjacent to Carroll Island, also known as "Paahwoke-it"), 200 murres were recorded, but since then, only small numbers of murres have been observed sporadically in 1917 and 1978 (Speich and Wahl 1989; Appendixes F and G). On 13-17 July 1959, a combination of aerial and boat surveys of seabird colonies was conducted along the Washington outer coast, which recorded 4,450 murres at seven locations plus 550 at sea off Cape Flattery (Kenyon and Scheffer 1%2). The largest colonies were at Carroll Island and Willoughby Rock (2,000 murres each, but they were uncertain of exact locations) with smaller colonies at Tatoosh Island (200) and White Rock (100). Small numbers (100) were noted at Bodelteh Islands on 13 July 1959 but none were recorded on 17 July 1959; fewer than 100 murres were noted in 1978- 79 but none between 1980 and 1995 (Speich and Wahl 1989; Appendixes F and G). Murres noted at "Flanery Rocks" in 1914 may have referred to Bodelteh Islands or White Rock (Jewett et al. 1953; Speich and Wahl 1989). At Cake Rock. 50 murres were noted on 13 July 1959; small numbers (25-175) were noted in 1967, 1990, and 1992 (Speich and Wahl 1989; Appendixes F and G). We have considered sporadic observations of murres at Bodelteh Islands and Cake Rock to reflect irregular attendance. Various other observations at several known colonies between 1907 and 1959 indicate long-term use of many colony sites (Jewett et al. 1953; Speich and Wahl 1989). Manuwal and Campbell (1979) summarized data firom USFWS aerial surveys (visual estimates from fixed- wing aircraft) conducted in the early 1 970s and tabulated 1 1 ,950 murres at 1 1 locations. The largest estimates of the numbers of murres present were reported at Grenville Arch (3,000), Willoughby Rock (3,000), and Split Rock (2,100). Smaller colonies were found at Point Grenville 56 USGS/BRD/ITR-2000-0012 (1,100), Quillayute Needles (900), James Island (750), Cake Rock (300), White Rock (250), and Tatoosh Island (100). Murres have not been otherwise observed on James Island, but are known to occupy adjacent rocks now known as Petrel Island ( "Kohchaa[uh]") and Gunsight Rock. Quillayute Needles represents a colony complex with several recent colonies: Huntington Island, Cakesosta, and Table Rock. In addition, murres were reported in the early 1 970s at Flat Rock south of Split Rock (300) and Giant's Graveyard (150; Speich and Wahl 1989). These observations apparently reflect irregular attendance or colony misidentification. At Point Grenville and Giant's Graveyard, specific islands attended by murres were not identified. Many of Washington's largest murre colonies are located on top of flat-topped sea stacks or islands (see Appendix I: Figures 1-33 to 1-37). It is impossible to see all attending birds, and in some cases even to determine if murres are present, when circumnavigating these islands by boat. In historical information, it is also unclear whether all colonies were surveyed, if counts on adjacent colonies were lumped and reported under one colony name, or if colonies were properly identified. In addition, murre attendance at colonies in 1906-07, 1 959, and the early 1 970s may have been affected by El Niiios (Quinn et al. 1987). Colonization of Tatoosh Island by 1956 indicates the population may have expanded in the mid-twentieth century. Suspected increases may reflect lower levels of activities by native people along the coast because of changes in traditional lifestyles. For example, camps of native people on Tatoosh and Destruction islands were abandoned. However, the decline of native populations and the rate of arrival and number of Euro-American settlers in western Washington was not as pervasive or extensive as in California and Oregon. Native people were confined to reservations along most of the outer coast and early settlers in the 1 880s and 1 890s tended to move into Puget Sound or the eastern areas on the Olympic Peninsula (Evans 1983). Large coastal areas were included in Mount Olympus National Monument and Olympic National Forest in the early 1900s. Some of these areas became part of Olympic National Park in 1938. Much of the outer Washington coast also remained inaccessible by land until 1931 when the Olympic loop highway (i.e.. Highway 101) was completed. Thus, the outer coast of Washington was spared from many effects from early settlers. Military bombing of Sea Lion Rock (north of Willoughby Rock) in southern Washington occurred from 1944 to 1992 (Speich et al. 1987). Carroll Island, Rounded Island, Sea Lion Rock, and Split Rock also were practice bombing targets during World War II and were bombed extensively with heavy ordinance. Several murre colonies were probably affected by low-flying aircraft en route to and from Sea Lion Rock and other target islands, including Willoughby Rock, Split Rock, and possibly Grenville Arch. Similar problems probably occurred after World War II. Lighthouse keepers and associated activities may have prevented breeding at Tatoosh Island from the late nineteenth century to the 1950s, but rats (Rattus spp.) and cats {Felis cams) were not introduced (Kenyon and Scheffer 1962). An accidental fire caused by researchers at Carroll Island burned the top of the island in 1969, but it is unclear if murres were affected since they bred on other parts of the island at that time (M. L. Cody, personal communication). Current Population Size and Distribution of Breeding Colonies in Washington During 1979-95, murres were recorded at 32 different locations along the outer coast of Washington (Appendixes F and G). Most counts at these locations did not provide information on the breeding status of attending birds. Eighteen locations have been designated as colonies (Figure 2.9) based on historical or recent observations of breeding (i.e., eggs or chicks seen) or regular attendance of rocks with suitable breeding habitats. As noted above, historical breeding (pre- 1979) had been confirmed only at Carroll Island and Willoughby Rock (Dawson 1907; Jones 1909; Jewett et al. 1953). In 1980-82, U. W. Wilson (unpublished data) observed chicks during the last week of June and first week of July at Grenville Arch, Split Rock, Willoughby Rock, and Cakesosta. On 27 August 1985, S. M. Speich collected one egg at Grenville Arch and four eggs at Willoughby Rock (WFVZ Nos. 149,537-149,541). On 4 September 1985. S. M. Speich collected an abandoned egg at Split Rock (WFVZ No. 149,536). On 3 June 1987, F Dobler (unpublished data) collected several murre chicks near colony departure that were accidentally killed on Jagged Island. On 19 June 1995, U. W. Wilson (unpublished data) observed medium-sized chicks on Huntington Island, and noted several large young on 13 July 1995 at this colony. On 18 July 1995, U. W. Wilson (unpublished data) and G. Burrell visited Carroll Island and found one abandoned murre egg. Murres breed regularly at the Tatoosh colony complex where long-term studies of murre behavior and reproductive success are under way (Paine et al. 1990; Parrish 1995). Breeding may have occurred at several of the other 14 sites but adequate documentation (see below) to confirm breeding status is lacking. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 57 To examine population trends, we divided locations attended by murres into two geographic sections, southern Washington — with 6 known colonies in Grays Harbor County — and northern Washington — with 12 known colonies in Clallam and Jefferson Counties (Figure 2.9). These areas had been identified in previous studies as having different murre population trends (Wilson 1991 ; Parrish 1995). No murre colonies have ever been reported in the inland marine waters of Washington's Juan de Fuca Strait, San Juan Islands and Puget Sound (Speich and Wahl 1989). Murres were counted annually by the USFWS along the outer coast of Washington from 1979 to 1995, except Tatoosh Island which was surveyed aerially only in 1994-95 (Appendixes F and G). Routine aerial surveys were not conducted at the Tatoosh Island complex from 1979 to 1993 because this colony was not part of the Washington Islands National Wildlife Refuge (consisting of Flattery Rocks, Quillayute Needles, and Copalis National Wildlife Refuges). Few birds (e.g., 200 birds in 1978: Speich and Wahl 1989) attended Tatoosh colonies (Appendixes F and G) in the late 1970s. By adding 200 birds to the USFWS 1979 aerial survey total of 3 1 ,520 birds for all other locations, a total count of 31,720 birds for 1979 was derived. Speich and Wahl (1989) derived a similar total (30,780 birds) by combining raw counts from the late 1 970s and early 1980s. By applying a it correction factor to the 1979 total, we estimated the breeding population for Washington at about 53.000 breeding birds. Southern and northern Washington accounted for 86% and 14%, respectively. In late June 1989, murre colony counts in Washington were conducted by a private consulting firm (Briggs et al. 1992) but, because of numerous problems (i.e., different survey techniques and incomplete surveys), we relied only on data from standardized USFWS surveys for trend assessments (see Appendix A). However, if we add 830 birds for Tatoosh Island (Briggs et al. 1 992) to the USFWS total of 3,925 birds (which excluded the Tatoosh Island complex), a total count of 4,755 murres was derived for 1 989, which corresponded to about 7,900 breeding birds. Certainly, numbers of murres in Washington were much lower in 1 989 than in 1 979 (Figure 2.10), and only 28% occurred in southern Washington. In 1994 and 1995. breeding population estimates for murres in Washington were 5.900 and 9.600 breeding birds, respectively, based on the results of the 5 July 1994 and 25 June 1995 USFWS aerial photographic surveys (Appendix G), which included the Tatoosh Island complex. The Tenyo Maru Oil Spill National Resource Trustees (2000) estimated the 1995 murre population in Washington at 1 3,600 birds by adding a median count of 5,230 birds from USFWS 1995 refuge surveys (excluding Tatoosh Island) to a 1995 ground count of 3,720 murres on Tatoosh Island (Parrish 1996) and applying a k correction factor of 1 .6. The proportion of Washington murres attending southern Washington locations was between 1 and 14% in 1994—95. In southern Washington, colonies occur in complexes at Point Grenville and Split-Willoughby. Peak numbers were estimated in 1979 at Point Grenville (21,400 breeding birds) and in 1982 at Split- 40 Washington Hgae Z10. Trends in wtiole-colonv counts g for connnon murres in Washington, 1 979- | 1995, excluding Tatoosh colonies (see ^ Appendix H). period r-square p-value 1979-1995 0.468 0.002 1979-1986 0.745 0.006 1996 58 USGS/BRD/ITR-2000-0012 Willoughby (26,300 breeding birds). Between 1979 and 1982, breeding murres were centered at these colonies in southern Washington. However, all six colonies in both colony complexes were abandoned or severely reduced by 1994-95 (see below). In northern Washington, colonies exist in relatively small individual colonies and in three colony complexes: Quillayute Needles, Carroll-Jagged, and Tatoosh (Appendixes F, G). In 1979-82, relatively small numbers occurred in northern Washington, but in 1994-95 the Washington population was centered there. Many instances of irregular murre attendance at rocks, often by small numbers, have been documented in the past (see above), as well as during aerial surveys from 1979 to 1995 (Figure 2.9). Determining breeding activity is difficult in Washington because of colony inaccessibility and poor viewing conditions from adjacent mainland areas or boats. During surveys in 1979-95, murres were reported at eight locations on only one survey in 1 year (i.e.. Colony number 584 in 1989, 457 in 1986, 426 in 1986, 419 in 1987, 367 in 1985, 294 in 1985, 140 in 1986, and Jagged Pillar in 1991). We suspect that breeding did not occur at these locations. During this same period, irregular attendance occurred over 2-3 years at Cake Rock ( 1 990-92) and at Carroll Pillar (1993-95). At Jagged Pillar, 17 murres were reported in 1978 and 25 in 1982 (Speich and Wahl 1989). In the past, irregular attendance has been noted at Carroll Pillar, Cake Rock, Bodelteh Island, Flat Rock, and Giant's Graveyard. In addition, irregular attendance has been reported at "Dahdayla" near Cake Rock (2-30 birds in 1967-69), Half Round Rock (250 murres in 1981), and Quillayute Needle (35-276 birds in 1978- 80). Otherwise, murres were not reported at these locations (Speich and Wahl 1989; Appendix F). At Middle Rock, large numbers (range, 450-1,800) attended irregularly in 1985-86. Although attended for a few years, breeding is not suspected at Destruction Island or Colony number 355- 359. Murres were not reported attending Destruction Island from 1906 to 1987 (Speich and Wahl 1989; Appendix F). Between 250 and 650 birds were observed loafing around peripheral rocks annually from 1988 to 1992 (Appendixes F and G). In 1995, 215 murres were present, but no eggs or chicks were found during ground visits to the island (U. W. Wilson, unpublished data). Destruction Island lacks suitable murre nesting habitat and murres were present in association with nesting Brandt's cormorants on the island's peripheral rocks. On the Washington coast, small numbers of nonbreeding murres frequently are seen among nesting Brandt's cormorants. Since these cormorants can change their colony locations, irregular murre attendance at certain rocks may be due to attraction of murres to Brandt's cormorant colonies. Figure 2.11. Trends in whole- colony counts for four colony complexes of common murres in Washington, 1979-1995 (see Appendix H). I s E o 2 « B a Z Carroll - Jagged Quillayute Needles 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 Willoughby - Split 0 T 1 1 1 1 1 1 1 1 1 1 1 1 1 1 • — I 1 1 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 Point Grenville ■ ■ P f P T W ¥ ■ ■ ■ ■ 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 Year BIOLOGY AND CONSERVATION OF THE COMMON MURRE 59 40 35 - 30 Hgure Z1Z Trends in whole-colony counts ^ for common murres in southern | Washington. 1 979-1 995 (see Appendix H). g E o u £ 25- 20- 15- Southem Washington \ ■ ■ W period r-sauare p-value 1979-1995 0.710 <0.001 1979-1986 0.743 0.006 1984-1995 0371 0.035 1 t 1996 Year Population Trends in Southern Washington, 1979-1995 Overall numbers of breeding murres in Washington declined 32.9% per annum between 1979 and 1986 (P= 0.006; Figure 2.10). Most decline between 1979 and 1986 occurred in southern Washington where steep downward trends occurred at colony complexes (Figure 2.11), as well as for southern Washington overall (43.7% per annum. P - 0.006; Figure 2. 1 2). During the period 1979-82. the southern Washington population was much higher than between 1983 and 1995, when numbers varied extensively at colonies and colony complexes (Figure 2.11: Appendix F). Murre attendance at the Point Grenville complex decreased greatly from 1979 to 1981 before rebounding in 1982. At the Willoughby-Split complex, both colonies decreased greatly in 1980 between similar peak numbers in 1979 and 1982. Large differences in the numbers of murres attending colonies in southern Washington between 1979 and 1982 apparently were related to natural and anthropogenic factors. In 1981, reduced colony attendance probably reflected a response to unusually warm surface waters (similar to moderate El Ninos) off the Washington coast between January and April 1 98 1 (Wilson 1991). Numbers of murres attending colonies increased in 1982, apparently reflecting the return of birds that did not breed, remained at sea, or moved temporarily to other colonies in 1980-81. In addition to the warm water episode, various human disturbances such as overflights and military activity occurred along the Washington coast on a regular basis in the late 1970s and early 1980s (Speich and Thompson 1987). These disturbances may have contributed to oscillating colony attendance. Death of common murres from entanglement in Washington gill-net fisheries (i.e., Willapa Bay. Grays Harbor, Puget Sound) in the 1970s and early 1980s probably occurred but was poorly documented. In 1983. widespread colony abandonment occurred in association with severe El Nino conditions (Wilson 1 99 1 ). Almost complete abandonment occurred at the Willoughby-Split complex by 1 984—86. Impacts from chronic colony disturbances and the 1981 warm water event also may have contributed to this steep decline. The negative effects of private aircraft overflights and military practice bombing of Sea Lion Rock on murre attendance at southern Washington colonies in 1984-85 was documented by Speich et al. (1987). Colony attendance was significantly reduced because of lingering effects of the 1982-83 El Nino during this study, therefore, the full effect of these military disturbances on breeding colonies was unclear. However, such disturbances undoubtedly affected many murre colonies until military bombing and aircraft overflights were greatly reduced in 1992. In 1984—85, disturbance by commercial ground-fishing boats was noted at Point Grenville and Willoughby Rock (S. M. Speich, personal communication). Limited increase between 1984 and 1988 may have reflected the return of some birds and the recruitment of subadults from higher populations in 1981-82. In 1988, numbers of murres attending colonies again began to dwindle to very low levels during the 60 USGS/BRD/ITR-2000-0012 1987-88 El Nino (Wilson 1991). From 1988 through 1995, natural and severe anthropogenic factors acted in concert to affect the murre population. In December 1988, an estimated 30,000 murres were killed off the outer Washington coast as a result of the Nestucca oil spill (Ford et al. 1 99 1 ). Because large numbers of murres from breeding colonies in Oregon, and possibly British Columbia, are found along the Washington coast during the fall and winter months (Manuwal and Carter 2001 ), these deaths probably involved murres originating from colonies in Washington and other areas. The proportion of murres from each area of origin killed by the Nestucca spill is unknown. Following the July 1 99 1 Tenyo Maru spill, Warheit (1996) estimated that 39-58% of the adult murres killed by this spill originated from Washington. Based on estimates of total mortality (3,740-19,559 murres), the Tenyo Maru Oil Spill Natural Resource Trustees (2000) concluded that a sizable portion of the total Washington state murre population (including nonbreeding adult, subadult, and juvenile birds) may have been killed in the spill. Between 1991 and 1994, onboard observer programs in various Washington gill-net fisheries documented seabird deaths from entanglements. Further studies in selected Puget Sound fisheries confirmed that common murres represented the majority of the total seabird entanglement (Jefferies and Brown 1993; Erstad et al. 1994; Pierce et al. 1994). In addition to deaths from oil spills and gill nets documented in the early 1990s, low colony attendance and reduced breeding effort occurred in 1993 during the severe 1992-93 El Nino. By 1994-95, small numbers still attended colonies in the Point Grenville complex but almost no birds attended the Willoughby-Split complex. At these low levels, it is doubtful if any murre breeding was still occurring in southern Washington. In summary, numbers of murres attending colony complexes in southern Washington declined 25.5% per annum between 1 979 and 1 995 {P < 0.00 1 ; Figure 2.12; Appendix H). Several types of anthropogenic and natural factors apparently acted in concert to greatly affect the population and prevent recovery. These include severe El Nifios, chronic human disturbance, and direct deaths from oil spills and gillnet entanglement. These factors presumably resulted in low colony attendance, reduced breeding success and recruitment, increased movements within and outside colony complexes, and deaths at sea. Since the southern Washington population constituted 86% of the entire Washington population in 1979-82, this change represents loss of most of the breeding population of murres within the state of Washington. Thus, overall numbers of breeding murres in Washington also declined 13.3% per annum between 1979 and 1995 (P = 0.002; Figure 2.10). The factors affecting the three largest colonies (Grenville Arch, Willoughby Rock, and Split Rock) are largely responsible for the Washington murre decline. Whereas murre colony attendance during severe El Nino years is generally reduced (Wilson 1 99 1 ) because of changes in the marine food chain (Wooster and Fluharty 1 985), the manner in which anthropogenic and natural factors acted to contribute to the decline, and how they may have prevented recovery, are difficult to determine with available evidence. Population Trends in Northern Washington. 1979-1995 Between 1979 and 1982, numbers of murres attending colonies varied extensively at individual colonies, colony complexes, and overall in northern Washington (Figures 2.11 and 2.13; Appendixes F, G, and H). As in southern Washington, widespread colony abandonment occurred in association with the severe 1982-83 El Nino (Wilson 1991). Colony attendance at the Quillayute Needles complex returned to 1979-82 levels (excluding 1981) between 1987 and 1995 (Appendix H). This increase may have reflected return of some breeding birds which had not attended colonies during surveys in 1983-84 or movements of birds from other colony complexes. At the Carroll-Jagged complex, substantial increase and more regular attendance occurred in 1987-95 than in 1979-86. At this complex, there was an apparent shift of birds from Jagged Island to Carroll Island. U. W. Wilson (unpublished data) considered no birds to be breeding at Carroll Island in 1995, although egg laying and breeding-site failure may have occurred prior to surveys. The lack of recovery at Rounded Island colonies, located closest to southern Washington, may have reflected similar conditions as experienced in southern Washington including a combination of effects from natural and anthropogenic factors. With the exception of Navy practice bombing, the same factors affecting murres in southern Washington also affected the northern colonies (e.g., severe El Ninos and gill-net and oil-spill deaths). At Tatoosh Island and associated rocks (Colony numbers 022, 023, 035), aerial photographic surveys were not conducted until 1994-95 when moderate numbers were recorded. Murres have been reported at this colony since 1956 (Speich and Wahl 1989). Paine et al. (1990) reported fewer than 1,000 birds during 1956-79, with a sharp increase to 2,000 birds during the eariy 1980s. Briggs et al. (1992) reported 830 birds in 1989. By 1992, islandwide attendance reached 3,871 birds, based on ground counts, ground estimates, and 35 ^ 3t Figure 2.13. Changes in whole-colony counts for common murres in northern Washington, 1979-1995 (see Appendix H). S s o 9 e 25 20 15 !• BIOLOGY AND CONSERVATION OF THE COMMON MURRE 61 Northern Washington 1978 1980 1982 1984 1986 1988 Year 1990 1992 1994 1996 photographs taken from boats (J. K. Parrish, personal communication). In 1 995, a USFWS aerial count of 1 ,705 birds was obtained on 27 July, corresponding to an estimate of 2,800 breeding birds. This estimate is similar to the 1 995 ground-based estimate of 3,270 breeding birds (J. K. Parrish, personal communication). In Washington, Tatoosh Island is currently the only murre colony where murre reproduction has been studied, and is the only colony for which there is evidence of consistent breeding (Parrish 1996). However, murres on this colony have recently experienced adult deaths and reduced reproductive success because of predation and harassment by bald eagles (Parrish 1995; Parrish and Paine 1996). The peregrine falcon population also has increased along the outer coast of Washington (Wilson et al. 2000) and may affect murre colonies (Parrish 1995). Limited increase in the northern Washington population occurred after the severe 1 982-83 El Nirio, in contrast to a lack of recovery in southern Washington. Both areas apparently have been subjected to similar problems (i.e., human disturbance, deaths from gill-net fishing and oil spills, reduced colony attendance during El Niiios and other warm water events, and possible impacts from climate change). The large and sustained increase in murres attending Tatoosh Island indicated that immigration has contributed to the growth of this northern Washington colony along with the return of first-time breeders natal to Tatoosh colonies (Parrish 1995). This rapid increase of the Tatoosh complex and increase at the Carroll-Jagged complex in the early to mid-1980s occurred at the same general time as the marked declines at both southern and other northern Washington murre colonies. Overall, the murre population in Washington significantly declined between 1979 and 1995, with the steepest rate of decline occurring between 1979 and 1986. Colony attendance dropped most dramatically during the severe 1982-83 El Nifio. Recovery after this event has been poor because of the effects of additional El Nirios, continued chronic gill net and oil spill associated deaths, and disturbance from military practice bombing and low aircraft overflights through 1992, Since northern Washington constituted only 14% of breeding murres in Washington prior to 1983, the small relative increases in northern Washington from 1984 to 1 995 have not significantly changed the status of the common murre in Washington to date. British Columbia Historical Background on Breeding Colonies in British Columbia, 1900-1979 Historical records for murre colonies in British Columbia are scarce and mostly anecdotal. Early in the twentieth century, large colonies were reported on Triangle Island at the northwest tip of Vancouver Island and on the west coast of Graham Island in the Queen Charlotte Islands. Smaller colonies were reported on the west coast of Vancouver Island at Solander Island and near Ucluelet (Figures 2.14 and 2.15; Brooks and Swarth 1925; Tavemer 1928). Subsequent breeding was 62 USGS/BRD/lTR-2000-0012 Forrester Island — ■ Langara Island — QUEEN CHARLOTTE ISLANDS ■ Cone Islet ■ Anthony Island Kerouard Islands — Kitimat Rock attended w/o confirmed breeding Figure2.14. Distribution of common murre colonies in northern Bntish Columbia and the southern edge of Alaska. Figure 2.15. Distribution of common murre colonies in southern British Columbia. Triangle Island scott islands \ '> Sartme Island '.a «*. QUATSINO SOUND • Solander Island — KYUOUOT SOUND - A Cleland Island I White Islet A Florencla Island A Starlight Reef- 0 25 50 Kilometers BRITISH COLUMBIA Vivian Island Rock attended w/o confirmed breeding Long-inactive colony Recently-inactive colony BIOLOGY AND CONSERVATION OF THE COMMON MURRE 63 documented at Triangle Island and near Ucluelet but not at Solander or Graham Islands. Triangle Island has been consistently identified as the main murre colony in British Columbia (Brooks and Swarth 1925; Drent and Guiguet 1961; Rodway 1991 ). Breeding was documented as early as 1900 and has been recorded on all subsequent ornithological expeditions to the island (Kermode 1904; Guiguet 1950; Carl et al. 1 95 1 ; Drent and Guiguet 1 96 1 ; Vermeer et al. 1976b; Rodway et al. 1990b; Parrish 1997). A weather station and lighthouse were abandoned in 1921 (Beebe 1960). Between 24 June and 1 July 1949, murre breeding was well documented during a collecting trip by the British Columbia Provincial Museum (now Royal British Columbia Museum [RBCM]; Guiguet 1950; Carl et al. 1951; Drent and Guiguet 1%1). Drent and Guiguet (1961) reported 19 eggs collected, although 26 eggs are currently preserved in collections at the RBCM (numbers El 149, E2025-E2038, E228-E229) and the UBCZM (numbers 787-795). One adult male also was "taken off egg" by C. J. Guiguet on 28 June 1949 (RBCM number 9853). In addition, colony size was estimated to be about 1 .500 breeding pairs, but egg laying had just commenced (Drent and Guiguet 1%1). C. J. Guiguet (unpublished field notes) provides additional details: "Several (7) large roosting colonies obser\'ed - each containing several hundreds of birds - nesting sites visited on edge of high cliffs north side - all nests at altitude 525 feet [ 160 m] - grassy tussocks at edge of sheer drop - eggs only - fresh. Majority of birds apparently haven't laid as yet in areas visited. Total population using island - several thousands." Several trips were made by the RBCM and British Columbia Ecological Reserves to Triangle Island in the 1960s and early 1970s but few details on murres are available. On 18 and 24 August 1966. small "two-day-old" chicks were collected (RBCM number 11642). On 24 August 1966, a larger chick (RBCM 11645) and an adult (RBCM number 1 1677) were collected. On 11 August 1974. "many small young" were noted and one egg was collected at Triangle Island (R. W. Campbell, unpublished data; RBCM number E 1 1 30). During seabird studies by the Canadian Wildlife Service, Vermeer et al. (1976a) conducted a complete count of 5.934 murres attending Triangle Island (i.e.. 5,384 on Puffin Rock and 550 on Castle Rock) on 29 July 1976. In 1977. lower anendance (about 3.000 birds) was noted when almost total breeding failure occurred for murres and tufted puffins Fratercula cirrhata (Vermeer etal. 1979). Breeding was confirmed at Sartine Island, near Triangle Island (Figure 2.15). where 236 and 600 murres were observed on ledges in 1 968 and 1 975, respectively (Hancock 1 97 1 ; Vermeer et al. 1 976a). EarUer breeding had not been reported in 1 950 at Sartine Island or, to the east, at Beresford, Cox, and Lanz Islands (Carl et al. 1951). Mink (Mustela vision) and raccoon {Procyon lotor) were introduced to Cox and Lanz Islands in 1938- 39 and extirpated nesting Cassin's auklets (Ptychoramphus aleuticus: Carl et al. 1951; Beebe 1960; Drent and Guiguet 1961; Rodway et al. 1990b). Mammalian predators are not present at Sartine and Beresford Islands, which support large populations of burrow-nesting storm-petrels and alcids, but little breeding habitat for murres exists (see Appendix I: Figure M3; Rodway et al. 1990b). Early, unsubstantiated records of breeding murres along the central west coast of Vancouver Island (Kermode 1904; Brooks and Swarth 1925; Tavemer 1928) were not accepted in major historical summaries (Munro and Cowan 1947; Drent and Guiguet 1961), but these warrant reconsideration in light of subsequent, confirmed breeding at Cleland Island, Florencia Islet, and Starlight Reef. At Cleland Island, breeding was confirmed between 1969 and 1982 (i.e.. 1969-70. 1973- 77. 1979. 1982. and 1983). but not in 1967 (Campbell and Stirling 1968; Campbell 1976; Campbell et al. 1975. 1990; British Columbia Nest Records Scheme [BCNRS]. see Myers et al. 1957; H. R. Carter and S. G. Sealy, unpublished data; see Appendix I: Figure 1-39). Between 2 and 150 murres were reported between 1969 and 1982, but only 1 to 8 breeding pairs laid eggs. When last noted, in 1983, only three murres were seen that may not have been breeding (G. Kaiser, unpublished data). One and two pairs bred on Starlight Reef in 1975 and 1980, respectively (Hatler et al. 1978; BCNRS). One unsuccessful breeding attempt by a single pair was recorded at Florencia Islet in 1%9 (Campbell et al. 1975; Hatler et al. 1978), but no murres bred there in 1970, 1974, or 1979 (Campbell et al. 1975; BCNRS; H. R, Carter and S. G. Sealy, unpublished data). A series of observations at White Islet (between Florencia Islet and Cleland Island) between 1968 and 1970 suggested that 1-2 pairs may have attempted to lay eggs but breeding was not confirmed (R. W. Campbell, unpublished data). On 30 July 1968, 30 murres were noted near shore and two adults were seen in potential nesting habitats, but no eggs or chicks were noted after landing. On 4 August 1969, two adults were again seen in the same location on the rock but no eggs or chicks were found. No murres were noted on 28 June 1970, but one adult was again seen on land in potential breeding habitat on 25 August 1970. Murres were not noted to attend White Islet on 64 USGS/BRD/ITR-2000-0012 subsequent visits from 1972 to 1979 (R. W. Campbell, unpublished data). Solander Island is a large seabird colony on the northwest coast of Vancouver Island and contains much suitable breeding habitat (Figure 2.15). However, breeding murres were not observed in 1954, 1975, 1988, or 1989 (Guiguet 1955; Beebe 1960; Drent and Guiguet 1961; Campbell 1976; Rodway and Lemon 1990). We have classified Solander Island as a long-inactive colony, based on available habitat and historic reference as a breeding colony, but without details (Brooks and Swarth 1925). Although 20 murres were noted flying around Solander Island on 27 June 1975 (R. W. Campbell, unpublished data), these birds probably were not attending potential nesting areas. A large murre colony on the west coast of Graham Island in the northern Queen Charlotte Islands was reported by Haida native people from Masset (Brooks and Swarth 1925). Three large seabird colonies (i.e., Langara, Frederick, and Hippa islands) with some breeding habitat exist along this coast, but breeding murres were not reported in 1927, 1946-47, 1952, 1955- 58, 1970-71, 1977, or 1981-88 (Darcus 1930; Beebe 1960; Drent and Guiguet 1961; Campbell and Garrioch 1979; Rodway et al. 1994; C. J. Guiguet, unpublished field notes; S. G. Sealy, personal communication). Large numbers of murres were reported off Langara Island and along the north coast of Graham Island during summer of 1927, 1946-47, and 1952 (Darcus 1930; C. J. Guiguet, unpublished field notes). At Langara Island, Darcus ( 1 930) further noted no murre colonies. On 4 July 1 946, C. J. Guiguet (unpublished field notes) noted "six California murres sitting on the rocks below the lighthouse, near sea. This is the first dme I've observed these birds on land here". On 18 May 1947, he noted ". . . I have no clues on nesting of these birds in this area". A female with a fully developed egg was collected near Langara on 19 July 1930 (Gumming 1931; Munro and Cowan 1947). We have treated Langara Island as "rocks attended without confirmed breeding." We presume that accounts of large numbers of murres at sea off northern Graham Island during the summer were related to the large colony at nearby Forrester Island in southeastern Alaska (Figure 2.14) that has been documented since 1914 (Willett 1915; Gabrielson and Lincoln 1959; DeGange et al. 1977; Sowls et al. 1978; Slater 1997). In fact, Haida natives may have meant this colony in their original report. Osgood (1901) presumed breeding at the Skedans Islands off the east coast of Moresby Island but breeding was never confirmed subsequently. Breeding was first confirmed on the Kerouard Islands at the south end of the Queen Charlotte Islands in 1977 (Campbell and Garrioch 1979). This colony represents the northern limit of the known breeding range of the subspecies U. a. californica, and is the only confirmed common murre colony in northern British Columbia between Triangle Island and Forrester Island in Alaska. Although breeding was not confirmed, 10 murres were noted on land on 5 August 1977 at the northwest rocks at Anthony Island, north of the Kerouard Islands (R. W. Campbell, unpublished data; H. R. Carter, personal observation). On 3 and 4 June 1982, three birds were flushed from inaccessible cliffs (Rodway et al. 1990a; M. S. Rodway, personal observation). No murres were seen there in 1985 or 1986. In addition, 40 murres were sighted on an unnamed rock ("Cone" Islet) on the west coast of Moresby Island in 1977 (BCNRS; Rodway 1991). Rough weather prevented a close inspection of the rock to confirm breeding in 1977 and the site has not yet been revisited. Table 2.7. Summary of most-recent surveys of common murres at colonies in British Columbia, 1977-1 997. Colony Colony Number of Number of Survey number name murres counted breeding adults year Vancouver Island (Central West Coast) WV-550 Starlight Reef 0 0 1982 WV-520 Florencia Islet 0 0 1982 WV-020 Cleland Island 0 0 1997 Vancouver Island (North West Coast) WV-080 Solander Island 0 0 1988 SC-020 Sartine Island 113 0 1989 SC-010 Triangle Island 9,943 8,153 1989 Queen Charlotte Islands (South Moresby Island) WM-320 Kerouard Islands 200 164 1995 WM-180 "Cone" Islet 40 not confirmed 1977 Total 10,296 8,317 BIOLOGY AND CONSERVATION OF THE COMMON MURRE 65 Current Population Size and Distribution of Breeding Colonies in British Columbia In British Columbia, murres now breed almost entirely at Triangle Island (Table 2.7), and breeding no longer occurs at four of five other known colonies (Rodway 1991). Murres have not bred recently at Cleland Island, Florencia Island, or Starlight Reef in 1982, 1984, and since 1990 (Rodway and Lemon 1990; BCNRS; A. Dorst, personal communication). At Sartine Island, no murres attended cliffs in 1987 and 1989, but 440 and 1 1 3 murres were observed in nearby waters (Rodway et al. 1990b). At the Kerouard Islands, the highest numbers (400 murres) were counted on cliffs in 1987 (Rodway et al. 1990a). Annual records kept by tour-boat operators indicated intermittent attendance of small numbers of birds from 1989 to 1991, and 1994 to 1996 (200 murres in 1995), but none were observed in 1992-93 or 1997 (R. W. Campbell, unpublished data). On occasion, murres also have been noted on land at other locations wherein no breeding occurred — on 2 July 1974, five murres in breeding plumage were observed in intertidal habitats at Vivian Island and on 7 July 1 974, two murres were noted on a breakwater off the jetty at the Tsawassen ferry terminal (R. W. Campbell, unpublished data). Triangle Island was examined extensively from 1980 to 1985 (Vallee and Cannings 1983; Vallee and Carter 1987; Rodway 1990; Rodway et al. 1990b). During this period, murres bred in four main areas: Puffin Rock, Murre Rock, Castle Rock, and Southeast Point (Rodway 1990). On 10 July 1982, a partial count of 4,910 murres was obtained at the main colony on Puffin Rock. In 1984, about 12,000 murres were estimated on the water in early July, but all breeding attempts failed (see below) and only small numbers were present on the breeding slopes. In 1985, murres bred successfully, and 3,956 murres were counted in different breeding areas between 9 and 19 July. The most complete estimate of colony size for Triangle Island was made in 1989 (Rodway 1990). An average of 5,839 murres (range, 3,335-6,144) was derived from replicated counts of murres from boat photographs between 27 July and 17 August 1989. Numbers from four complete counts (between 1 800 and 2000 h [PDT] when daily attendance was highest) ranged from 5,846 to 6,144 birds. To determine a total number of birds attending the colony, the 5,839 mean count was adjusted with a "ground-truthing" or "g" correction factor of 1 .44. This correction factor was determined by averaging the difference between telescope and photo counts over the 0700-2100 period. Thus, 8,408 birds were estimated to attend photographed areas. An average of 1,535 murres in other areas (i.e., not photographed) were added to obtain a total of 9,943 birds. To derive an estimate of the number of breeding adults at the colony, a k correction factor of 0.82 was applied to derive 8,153 breeding birds or 4,077 breeding pairs. This estimate was higher than previous estimates due mainly to more complete coverage of the colony. A repeat of the survey using similar methodology in 1996 probably underestimated total numbers because some chicks and adults had departed from the colony before the count was completed (Parrish 1997). By adding recent complete counts of murres at Triangle Island and the Kerouard Islands, we obtained a total of 10,296 birds which corresponded to a total breeding population estimate for British Columbia of about 8.300 breeding birds (Table 2.7). Population Trends in British Columbia Historical records and recent data were inadequate to determine population trends in British Columbia. Colonization and abandonment of colonies along the west coast of Vancouver Island in the late 1960s and 1970s are difficult to interpret and may indicate an intermittent colonization event perhaps during a period of colony growth at Triangle Island and colonies in Washington. Replicated counts at three subcolony sites on Triangle Island in 1982. 1985, and 1989 were highest in 1982 and lowest in 1985 (Table 2.8; Rodway 1990). Counts were conducted at different times in the 3 years, but decrease between 1982 and 1985 and limited increase between 1985 and 1989 were similar to trends at certain northern Washington colony complexes (see Washington section). No murres bred successfully at Triangle Island in 1984 when complete breeding failure of murres and most other surface-breeding species occurred because of severe weather and prey shortage Table 2.8. Comparison of counts of common murres at subcolony sites on Triangle Island in 3 years from 1 982 to 1 989 (from Rodway 1 9901 Location Site number 1982 1985 1989 S side W f>oint W side W point Murre Rock 13,14 15 22, 25. top 1,140 648 1,843 540 400 740 790 523 1,466 66 USGS/BRD/ITR-2000-0012 (Rodway et al. 1990b, 1992). A partial failure also occurred in 1989. Large numbers of murre eggs had been eaten by glaucous-winged gulls (Larus glaucescens), but it was unknown whether predation contributed to abandonment or occurred afterward (Rodway 1990). Incubating murres that remained at breeding sites sat tight on their eggs when approached by bald eagles or peregrine falcons. Thus, it seemed unlikely that avian predators were the sole cause of failure. Large numbers of murres were killed by the 1988 Nestucca oil spill, but a distinct change in the breeding colony at Triangle Island could not be detected (Rodway et al. 1989, 1990b; Burger 1992). Overall Population Assessment Current Population Size and Distribution of Breeding Colonies A complete assessment of the total size and distribution of the overall breeding population of the common murre in California, Oregon, Washington, and British Columbia has been made only once, over a 2-year period from 1988 to 1989. During this period, the overall estimated breeding population was approximately 1 . 1 million breeding birds (Table 2.9; see Carteret al. 1995). Several previous population estimates of common murres for this portion of western North America were lower and less reliable. Tuck (1961) roughly estimated not more than 1 million murres for California and Oregon without details, and it was not clear if breeding and nonbreeding birds were included in the estimate. Byrd et al. (1993) used a combination of 1979-89 data and reported a total of about 826,000 breeding murres: California (363,000 in 1979-80; Sowls et al. 1980), Oregon (426,000 in 1988; R. W. Lowe, unpublished data), Washington (3 1 ,000 in 1 978-79; Speich and Wahl 1989), and British Columbia (6,000 in 1988-89; Campbell et al. 1990). However, large population declines occurred in central California and Washington between 1979 and 1989, which makes this combination of data less reliable. Tyler et al. (1993) reported 810,500 breeding murres (minus British Columbia): California (35 1,000 in 1989; Carteret al. 1992), Oregon (438,100 in 1989; Briggs et al. 1992), and Washington (21,400 in 1989; Briggs et al. 1992). We relied on data largely from the USFWS for murre numbers in Washington and Oregon to maximize compatibility among data sets used to generate population estimates. Rodway (1991) reported 8,640 breeding birds for British Columbia; this estimate was based on the same information as the 8,300 breeding birds estimated in this report. From 13.0 to 20.7 million breeding individuals, or 6.5 to 10.3 million breeding pairs, of common murre have been estimated in the world, with 54-57% and 43^6% in the Pacific and Atlantic Oceans (including adjacent areas of the Arctic Ocean), respectively (Nettleship and Evans 1985; Byrd etal. 1993; Ainley et al., in preparation). The breeding population in California, Oregon, Washington, and British Columbia (about 1.1 million breeding birds) constitutes 5-8% and 13-28% of the breeding population size of the world and the Pacific Ocean, respectively. The common murre is the most abundant breeding species of seabird in central California, northern California, and Oregon (Sowls et al. 1980; Varoujean and Pitman 1980; Carter et al. 1992, 1995; Tyler et al. 1993; R. W. Lowe, unpublished data). Suitable habitat (small, bare, nearshore rocks) is abundant and widely distributed along these coasts. Habitat availability and the ability of murres to exploit various abundant prey resources in many different marine habitats near shore and throughout the continental shelf have enabled murres to exist in high abundance within this geographic area. In Washington, Cassin's auklets, rhinoceros auklets (Cerorhinca monocerata). and glaucous-winged gulls are more numerous than murres (Speich and Wahl 1989). In south-central California, the Brandt's cormorant becomes the most numerous species of breeding seabird and murres no longer breed south of Monterey County (Hunt et al. 1980; Sowls et al. 1980; Carter etal. 1992). Murres have achieved large breeding populations at most colonies in northern California and Oregon in recent decades, probably in Table 2.9. Total sum of common murres counted and numbers of breeding adults estimated in California, Oregon, Washington, and British Columbia in 1 988-1 989. Year Total Number of Percent Geographic area counted sum' breeding adults of total Central California 1989 53,985 90.200 8.4 Northern California 1989 156,555 261,400 24.2 Oregon 1988 426,278 711,900 66.0 Washington 1988 4,190 7,000 0.6 British Columbia 1989 10,296 8,300 0.8 Total 651,304 1,078,800 ^Sum of whole-colony counts at all colonies in a geographic area. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 67 response to the relatively low levels of colony disturbance and anthropogenic mortality, and excellent prey conditions within the central part of the California Current upwelling system (Briggs et al. 1987; Ainley and Boekelheide 1990; Tyler et al. 1993; Manuwal and Carter 2001). About 66% of the overall breeding population of common murres (U. a. califomica) is present in Oregon (Table 2.9). More than 420.000 murres were estimated breeding along the central and north coasts of Oregon with the largest colonies at Bird Rocks. Three Arch Rocks, Two Arches Rock complex, and Gull and Colony Rocks near Newport. The southern Oregon coast contained approximately 290.000 breeding murres with the largest colonies at Cat and Kittens. Gull Rock (Cape Blanco). Orford Reef. Island Rock. Hubbard Mound Reef. Mack Arch, and outer Whaleshead. Significant numbers (24%) also bred in northern California, mainly on several large offshore rocks in Del Norte and Humboldt Counties (especially Castle Rock. False Klamath Rock. Green Rock. Flatiron Rock, and False Cape Rocks). Combined. Oregon and northern California comprise the current population "core" or 90% of the breeding birds which form the geographic center of the entire U. a. califomica population. This "core" area is located in the central part of the California Current upwelling system, characterized by strong and persistent upwelling during the spring and summer (Briggs et al. 1987; Tyler et al. 1993). Prey resources and breeding habitat in the area appear to have been sufficient to sustain this major part of the population from 1979 to 1995. Historically, very large numbers of murres were present in central California, which also is located within the central part of the California Current upwelling system (Briggs et al. 1987; Ainley and Boekelheide 1990; Tyler et al. 1993). In the early nineteenth cenmry, central California had a much larger proportion of breeding murres before near extirpation of the immense colony at the South Farallon Islands. This colony may have totaled 1-3 million breeding birds at its peak. By 1989. the number of breeding murres in central California was at the lowest recorded level between 1979 and 1995 and comprised only about 8% of the total population of breeding murres (Table 2.9). In 1979-82, more than twice as many murres bred in central California than in 1989. The largest colonies were present at the South Farallon Islands. North Farallon Islands, and Point Reyes. Presently, the southernmost colony in California is in central California at Hurricane Point Rocks. In the past, murres bred as far south as Prince Island in the Channel Islands off southern California. The southern limit of the breeding range of the common murre in the eastern Pacific Ocean is roughly aligned with the southern edge of the California Current upwelling system off southern California and western Baja California, where colder subarctic waters are diluted by warmer waters from the central ocean gyre (Tyler et al. 1993). Several other alcids also reach their southern limit in southern or central California (i.e.. pigeon guillemot [Cepphus columba]. marbled murrelet [Brachyramphus mannoratus], rhinoceros auklet. and tufted puffin) or their northern limit (i.e.. Xantus's murrelet [Syiuhliboramphus hypoleiicus]: Hunt et al. 1980; Sowls et al. 1980; Carter et al. 1992; Gaston and Jones 1998). A major change in climate, breeding habitats, prey resources, and natural predators occurs in this area, which affects breeding by several breeding seabird species (Hunt et al. 1980; Briggs et al. 1987; Carter et al. 1992; Tyler et al. 1993). In addition, large populations of native peoples used mainly marine food resources and probably prevented breeding in many parts of the Channel Islands off southern California for thousands of years (e.g.. Glassow 1980) until they were extirpated from the area in the mid-nineteenth century. In the nineteenth and twentieth centuries, early European and American settlers also affected seabird populations in southern California and northwestern Baja California, with egg-collecting activities, introduction of predators to islands (McChesney and Tershy 1998). and other activities. Thus, the southern limit of breeding murres U. a. califomica may have occurred in the southern California or possibly northwestern Baja California for at least tens of thousands of years. Breeding murres in Washington represented less than 1% of the total breeding population of U. a. califomica in 1988-89 (Table 2.9) but were several times more numerous between 1979 and 1982. The few colonies in British Columbia also comprised less than 1% of total breeding population (Table 2.9). Most birds in British Columbia bred at one isolated colony at Triangle Island, at the north tip of Vancouver Island. Other colonies are small, widely separated, and irregularly attended. The northernmost colony of U. a. califomica is located at the Kerouard Islands at the southern end of the Queen Charlotte Islands. There is no evidence that murres ever bred more widely in British Columbia. A major change in breeding habitat occurs on the west coast of Vancouver Island. British Columbia, where most of the outer coast islands become forested, and those that are not tend to be small, low and rounded, and less suitable for breeding by murres and some other seabirds (Beebe 1960; Campbell et al. 1990). In comparison with Washington, Oregon, and California, 68 USGS/BRD/ITR-2000-0012 the availability of open breeding habitats on islands in British Columbia are reduced. Washington and southern British Columbia also are located at the northern end of the California Current upwelling system where it meets the Alaska Current during spring and summer (Morgan etal. 1 991; Tyler etal. 1993; Wahletal. 1993). Different prey resources are associated with the estuarine conditions within the extensive fiord system along the coasts of British Columbia and southeastern Alaska. Also, large populations of native people were present for at least thousands of years in British Columbia prior to the mid-nineteenth century (Duff 1997), and probably visited many seabird nesting islands to obtain eggs and birds for food. Certain murre colonies may have been extirpated prior to 1 800. However, reduced availability of breeding habitats and change in prey resources may be the primary factors contributing to the current geographic gap between murres breeding in Alaska (U. a. inornatd) and from southern British Columbia to California {U. a. califomica). During glacial periods in the last 1 million years (i.e., the last period ended about 10,000 years ago), continental ice sheets extended to sea level from northern Washington through much of southern Alaska, which coincides to a large degree with the current geographic gap and is related to changes in coastal topography. Glacial history probably is a major factor underlying the current gap in distribution, and also may have strongly influenced the current location of the major portion of the population of U. a. californica in Oregon and California. However, the fossil history of Uria extends back at least 5 million years in southern California (Barnes etal. 1981; Howard 1949, 1981, 1982; see Bedard 1985). Various changes in seabird communities, marine environments, and coastal topography have occurred in the North Pacific over millions of years and influenced the distribution and abundance of the common murre. Recent and Historical Population Trends The numbers and distribution of common murres in the Oregon and northern California "core" population between 1979 and 1995 seem to represent relatively stable high levels, possibly indicative of near carrying- capacity levels and distribution (Figure 2.16). In this area, murre numbers have stabilized for several decades, apparently in relation to available breeding habitat, prey resources, and relatively low levels of human disturbance at colonies. Most suitable breeding habitat is occupied, although some habitat has been removed historically by either connecting islands to the mainland with breakwaters or modifying islands for lighthouses or other structures. The abundance and availability of prey resources have not been well studied, but evidendy have been adequate to maintain populations at current high levels. Few natural factors are known that would disrupt this stability. Lower numbers of breeding birds Washington Oregon Figure 2.16. Changes in whole- colony counts of common murres at breeding colonies in central California (all colonies), northern California (excluding the Castle Rock colony), Oregon (15 sample colonies), and Washington (excluding Tatoosh colonies), 1979-1995. a e 9 z 20 ■*«~»-iil 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 120 100 80 60 40 2« Central California 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 Northern California 80 /*^ 4« 20 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996 Year BIOLOGY AND CONSERVATION OF THE COMMON MURRE 69 attended colonies during severe El Nirios in 1983-84 and 1992-93. These events probably caused lower prey availability or accessibility over the short term (e.g., Ainley and Boekelheide 1990). Resultant depressions in reproductive performance apparently have not had long-term effects on the size of the "core" populations in northern California and Oregon. Few anthropogenic factors have affected murres in Oregon and northern California in recent decades except in fall and winter when most Oregon birds move north to Washington and British Columbia. Some Oregon birds undoubtedly have been killed in gill nets and by oil spills in Washington and British Columbia (especially the 1988 Nestucca and 1991 Tenyo Maru oil spills) between 1979-95. Yet, despite such deaths, the "core" of the overall population did not change to a large degree. The large population size and the wide dispersal of anthropogenic deaths among many colonies may have lessened effects on the Oregon population. To reach current population levels, murres in northern California and Oregon had to recover over many decades (mainly from the 1940s to the 1970s) from extensive human impacts that occurred in the late nineteenth and early twentieth centuries. As impacts from native peoples and early settlers declined, the numbers and range of breeding murres increased to the current high papulation levels. During this period, colony formations (including recolonization events) occurred widely. Adequate prey resources, available breeding habitat, and relatively low natural or anthropogenic deaths must have existed for this recovery to occur. In northern California, extensive recovery has occurred in Del Norte and Humboldt Counties but recovery is still occurring in Mendocino and Sonoma Counties where recolonization events and population increase are ongoing. In central California, historical effects by early settlers reduced this population to low levels. Extirpation of colonies in Sonoma and. possibly, Mendocino counties may have caused the geographic gap between murres breeding in central and northern California. Colony extirpation was recorded at San Pedro Rock and near extirpation at the South Farallon Islands. By the early 1980s, many colonies had increased substantially, but were still well below known historical levels. As in northern California, adequate prey resources, available breeding habitat, and relatively low natural and anthropogenic mortality existed for this limited partial recovery to occur. Breeding habitat at the South Farallon Islands has been reduced from historical conditions, thus, it is unlikely this colony will ever return to levels reached in the early nineteenth century. Declines between 1982 and 1989 occurred at all colonies in central California and one colony (Devil's Slide Rock) was extirpated. Partial recovery in central California between 1989 and 1995 has been slow and limited, possibly reflecting the relative severity of the original decline, as well as continuing effects. Breeding success has remained high at the South Farallon Islands (except during severe El Ninos) and is not a factor impeding recovery at most colonies (Hastings et al. 1997; Sydeman et al. 1 997; McChesney et al. 1998. 1999; M. W. Parker, unpublished data). However, mortality from recent oil spills (e.g.. 1996 Mohican. 1997-98 Point Reyes Tarball Incidents, and 1998 Command) and the recent resurgence of significant deaths in gill nets in Monterey Bay have increased anthropogenic impacts since 1995 (P. R. Kelly, personal communication). In Washington, numbers of murres attending colonies in 1979-82 reflected growth since the early twentieth century. Decline and little recovery between 1982 and 1995 in Washington appear to have resulted from severe effects (from natural and anthropogenic factors) on the murre population over the long term (Figure 2.16). Murre attendance at the largest colonies in southern Washington (i.e.. Split Rock. Willoughby Island. Grenville Arch, and Rounded Island) plummeted to small numbers of irregularly-occurring birds and evidence of reproductive effort and success has been largely absent since the initial decline. Small colonies in northern Washington also declined, but to a lesser degree and have shown limited growth in recent years, possibly because of intercolony movements from southern Washington colonies. Massive decline and a lack of recovery in southern Washington may be related to the lower initial population size in Washington before the decline (compared with populations in Oregon and California), the high magnitude of natural and anthropogenic impacts over an extended period of time, and intercolony movements of birds to northern Washington colonies. However, small numbers of birds still attend traditional breeding colony locations in southern Washington and some recovery may be possible in the future. The likelihood of rapid namral recovery in Washington is very low because of continued anthropogenic and natural effects and the slow rate of murre recovery documented at severely reduced colonies elsewhere along the Pacific coast Overall, murre numbers in central California and Washington have declined substantially since the early 1980s and currently exist well below historical population levels and distribution (Figure 2.16). Major declines occurred rapidly between 1982-^6, and low numbers have remained over extended periods of time following these declines. Although limited increase has 70 USGS/BRD/ITR-2000-0012 occurred in central California in recent years, numbers remain depressed in Washington. Prey resources have been little studied but were apparently adequate to maintain these populations at higher population levels in 1979-82. Large-scale declines between 1979 and 1989 resulted from long-term impacts from anthropogenic factors (i.e., gill-net and oil-spill deaths and human disturbance), coupled with natural factors (i.e., reduced reproductive effort and success associated with severe 1982-83 El Nino, and the 1981 warm water event in Washington). At the same time, climate change has been occurring with a significant wanning of coastal waters which also may be affecting murre prey resources (Roemmich and McGowan 1995; Ainley et al. 1996). In central California, climate change has not prevented recent increase in the murre population, but may have reduced the rate of increase (Sydeman et al. 1 997). The apparent overall stability of populations in Oregon and northern California between 1979 and 1989 underscored the fact that natural factors alone were not responsible for major declines in central California and Washington (Takekawa et al. 1990; Carteret al. 1995). Washington populations now persist at extremely low levels and are affected by continuing anthropogenic and natural factors, which probably have prevented or slowed recovery. The status of common murres in British Columbia is poorly known. The isolated colony at Triangle Island has been present since at least the beginning of the twentieth century. At this colony numbers of breeding murres were relatively stable between 1982 and 1989. Small colonies on the west coast of Vancouver Island disappeared in the 1970s and 1980s. In the past, most potential breeding islands for murres in British Columbia probably were visited frequently by native people hunting seabirds. Murres on Triangle Island breed largely on inaccessible cliffs far from the coast of Vancouver Island, enabling this colony to coexist with native peoples over extended periods of time. Few Europeans or Canadians settled the outer west coast of Vancouver Island (except during a brief sardine fishery in the 1930s), which suggests that human effects were probably low during the twentieth century. However, mortality from oil spills or gill nets may have impacted these colonies, either during the breeding season (e.g., Barkley Sound; Carter and Sealy 1984) or in wintering areas in Juan de Fuca Strait, Puget Sound, or the Straits of Georgia. Acknowledgments This chapter has benefitted greatly from detailed reviews and editorial comments of various drafts by D. G. Ainley, D. Bertram, G. V. Byrd, A. J. Gaston, M. R Harris, K. Kilbride, G. J. McChesney, D. N. Nettleship, S. Olson-Edge, M. W. Parker, F. L. Paveglio, J. R. Sauer, S. G. Sealy, J. L. Trapp, and T. S. Zimmerman. Administrative support was provided by B. Bortner, D. L. Orthmeyer, and T. Zimmerman. Assistance with preparation of figures and tables were provided by M. Anderson, P. J. Capitolo, J. Daugherty, J. Friday, C. Gregory, G. J. McChesney, D. L. Orthmeyer, and W. Perry. In California, funding and support for murre colony surveys and aerial photograph counting from 1985 to 1995 were provided by USFWS, Humboldt State University, U.S. Geological Survey (Western Ecological Research Center), California Department of Fish and Game (Office of Spill Prevention and Response and Air Services), Minerals Management Service, U.S. Navy, U.S. Department of Justice, Point Reyes National Seashore, Apex Houston Trustee Council, and Point Reyes Bird Observatory. Administrative assistance was provided by D. G. Ainley, S. Allen, R. Coleman, D. S. Gilmer, R. T. Golightly, J. Hamby, L. Heitz, R. Helm, R. Johnson, T. W. Keeney, P R. Kelly, V. Lee, D. Lollock, D. L. Orthmeyer, M. W. Parker, M. O. Pierson, G. Reetz, W. J. Sydeman, E. Ueber, and D. Welsh. Aerial surveys were conducted in the Gulf of the Farallones and Monterey Bay National Marine Sanctuaries in 1993- 95 under permit numbers GFNMS/MBNMS 04-93, 02-94, and 04-95, with assistance by H. M. Golde, T. Jackson, S. Kathey, J. Roletto, and E. Ueber. Aerial surveys were conducted in the Channel Islands National Marine Sanctuary in 1991-95 under permit numbers CINMS 02-91, 04-92, 05-93, 02-94. 01-95, with assistance by M. Crosby, S. Jameson, J. A. Miller, J. Morris, J. A. Uravitch, and C. Wahle. Significant assistance with surveys or photograph counting were provided by L. Accurso-Vicenzio, P. J. Capitolo. T. E. Harvey, D. L. Jaques-Strong, D. L. Jory-Carter. R. W. Lowe, G. J. McChesney, W. R. Mclver, E. Nelson, L. K. Ochikubo, M. W. Parker, C. S. Strong, and D. L. Whitworth. Flights were conducted by Aspen Helicopters (Camarillo, California), California Department of Fish and Game (Air Services; Sacramento, California), and Northern Air Services (Eureka, California). We also greatly appreciate earlier efforts in 1979-82 to survey murre colonies with aerial photography in California by K. T. Briggs, A. R. DeGange, G. S. Lester, D. B. Lewis, J. W. Nelson, A. L. Sowls, and W. B. Tyler. We lament the tragic death of J. M. Drust, who piloted many aerial photographic surveys of murre and other seabird colonies in California in 1991-95. Funding and support for murre colony surveys and aerial photograph counting in Oregon from 1988 to BIOLOGY AND CONSERVATION OF THE COMMON MURRE 71 1995 and in Washington from 1979 to 1995 were provided by the USFWS and Tenyo Maru Trustee Council. Administrative assistance was provided by B. Hesselbart. J. E. Houk, J. Kincheloe. P. Sekora, and J. Welch. Significant assistance with surveys or photograph counting in Oregon were provided by J. Anderson, M. Naughton, D. Pitkin, and S. Reimer. Assistance with historical literature and unpublished data in Oregon and Washington was provided by R. Bayer, F. Dobler, M. Graybill, J. Hodder, D. B. Marshall. R. L. Pitman. S. M. Speich, D. Varoujean, and T. R. Wahl. Funding and support for murre and other seabird colony surveys in British Columbia from 1 980 to 1 989 were provided by Environment Canada (Canadian Wildlife Service, and Conservation and Protection), especially with 1989 funding for murre studies at Triangle Island related to the Nestucca oil spill, and with administrative assistance by S. Gamham, G. Kaiser, S. Wetmore. and K. Vermeer Significant assistance with surveys and design was provided by D. Bertram. B. Carter, D. Gamier, A. J. Gaston, D. Grinnell, M. Lemon, D. Powell. G. E. J. Smith, and K. Summers. Surveys in the 1970s were funded by Royal British Columbia Museum; British Columbia Ministry of Environment. Lands and Parks: and Parks Canada. Assistance with historical literature, unpublished data, and unpublished egg records was provided by C. Adkins, R. W. Campbell, A. Dorst, C. J. Guiguet, G. Kaiser, M. C. E. McNall, and S. G. Sealy. Also. R. W. Campbell provided certain colony photographs in Appendix I. We lament the tragic death of A. Vallee. who studied murres and other seabirds at Triangle Island in 1980-82. Valuable historical egg records in California, Oregon. Washington, and British Columbia were obtained from collections at Humboldt State University (Department of Wildlife Museum; Areata, California), Museum of Comparative Zoology (Harvard University. Cambridge, Massachusetts), National Museum of Natural History (Washington, D.C.), Royal British Columbia Museum (Victoria, British Columbia). San Diego Museum of Natural History (San Diego, California), Santa Barbara Museum of Natural History (Santa Barbara, California), University of British Columbia Zoology Museum (Vancouver. British Columbia). University of California (Museum of Vertebrate Zoology; Berkeley, California), and especially the Western Foundation of Vertebrate Zoology (Camarillo, California). Comments on Appendix B were provided by D. G. Ainley, G. J. McChesney, M. W. Parker, W. D. Shuford. L. E. Stenzel. W. J. Sydeman. and P. While. Valuable unpublished field notes containing historical information on murre colonies in California included C. I. Clay (Humboldt State University, Special Collections Library, Areata, California). H. L. Cogswell (unpublished data collated and provided by Howard Cogswell), and L. O. Williams (University of California Berkeley, Hastings Reservation, Carmel Valley, California). Invaluable assistance with the collation of historical egg records from museums was provided by G. J. McChesney, W. R. Mclver, R. T. Golightly. and T. Danufsky. S. F. Bailey (Pacific Grove Natural History Museum) provided a copy of the common murre section of the notebook files for the "Middle Pacific Coast Region" (Oregon border to Point Conception) maintained for American Birds and its predecessor Audubon Field Notes. This notebook file contains the unpublished observations of many individuals noted in the text and was checked against observations published in American Birds. The libraries of the University of Manitoba (Winnipeg. Manitoba), University of California (Davis and Bericeley, California), and Point Reyes Bird Observatory (Stinson Beach, California) provided much historical literature and assistance through interlibrary loans. Other unpublished historical observations were provided by S. Allen, R. A. Erickson. R. Jurek. and T. Schulenberg. Previous summaries of historical literature on murres in California were extremely helpful, especially the works of D. G. Ainley, R. W Doughty, J. Grinnell. G. L. Hunt. L. F Kiff, T. J. Lewis, A. H. Miller, and T. O. Osborne. Literature Cited Ainley. D. G. 1976. The occurrence of seabirds in the coastal region of California. Western Birds 7:33- 68. Ainley, D. G., and R. J. Boekelheide. editors. 1990. Seabirds of the Farallon Islands. Stanford University Press, Stanford, California. 450 pp. Ainley, D. G., and T. J. Lewis. 1974. The history of Farallon Island marine bird populations 1843- 1972. Condor 76:432-446. Ainley, D. G.. D. N. Netfleship. H. R. Carter, and A. Storey. In preparation. Common murre (Uria aalge). In A. Poole and F. Gill, editors. Birds of North America. The Academy of Natural Sciences, Philadelphia, Pennsylvania, and the American Ornithologists' Union, Washington, D.C. Ainley, D. G., L. B. Spear, S. G. Allen, and C. A. Ribic. 1 996. Temporal and spatial patterns in the diet of the common murre in California waters. Condor 98:691-705. 72 USGS/BRD/ITR-2000-0012 Ainley, D. G., W. J. Sydeman, S. A. Hatch, and U. W. Wilson. 1994. Seabird population trends along the west coast of North America: causes and the extent of regional concordance. Studies in Avian Biology 15:119-133. Ainley, D. G., and M. C. Whitt. 1974. Numbers of marine birds breeding in northern California. Western Birds 4:65-70. 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Western Foundation of Vertebrate Zoology, 439 Calle San Pablo. Camarillo. CaUfomia 93010 Briggs. Kenneth T., DanviUe Veterinary Hospital, 812 Camino Ramon Road. DanviUe. CaUfomia 94526 Campbell. R. Wayne. P O. Box 6218. Station C, Victoria. British Columbia V8P 5L5 Canada Qay, Charles I. (Deceased). unpubUshed field notes. Special Collections Library and WlldUfe Museum, Humboldt State University, Areata. California 95521 Cody. Martin L., Department of Biology, University of CaUfomia, Los Angeles, California 90024 Cogswell, Howard L. California 94541 1548 East Avenue, Havward, Dobler. Fred. Washington Department of Fish and Wildlife, 2108 Grand Boulevard, Vancouver, Washington 98661 Dorst. Adrian. 820 CampbeU Street, Tofino, British Columbia VOR 2Z0 Canada Erickson. Richard A., P. O. Box 1706, Lagiuia Beach, CaUfomia 92652 Ford. R. Glenn. R. G. Ford Consulting. 2735 N. E. Weidler Street, Portland Oregon. 97232 Guiguet diaries J. (Deceased). unpubUshed field notes. Vertebrate Zoology Division, Royal British Columbia Museum, 675 BeUeville Street Victoria, British Columbia V8V 1X4 Canada Jurek, Ronald. California Department of Fish and Game, Habitat Conserv ation Planning Branch. 1416 Ninth Street Sacramento, California 95814 BIDLDBY AMD ODW^RVATIOW OF Ttf COyyON MURRE 35> Gay W^ Canadian Wildlife San-ice, Pacific WiMKfe Research Centre. RR#]. 5423 Robeatson Road, DelUL Bntish Columbia V4K 3N2 Canada Bej^, Raid IL. Calif amia Deparaneni of Fish and Game, OfiEioe 'Of Spil Pirvexiticni aaod Rsspaasc, IIQO K Sheet, Sacrameirto. California 94244 Mantfcallll Da^-id B., 42i65 S, W. Chesapeake AA'enne, PntiaBd. Oregon 91101, wiprihJinhed field note^ 13S. Rsh and WildHfe Sexvioe. Oregon Coast Jiibitional WDdlife Rcsftige, 2127 S, E. OSU Drive. iilcwpoirL QregcBi 97365 cGcrard J., U.S. Geolopcal Sun'ey.'WfeStcaiB Bcologsca] Research Ceaaiei. Dixon FicM Sltaiinm, fi924 Tremoni Road. I>i»cm. California 95620, a«d HffimboldT Siaie Umvesrsfl^'. Department ofWiyBtfc, AvcaiUL. Cailiilamta '95521 Aldan H. (De.ceased). iinpublishe.d field i («f Venebraie Zoology, Universally of fJiffftT"", Bea^^eik^, Califonu Dawiid !NL 25 Tidewater Lane. AlOoi Nam SoDtta BOl 310 Caitaiia Parkor. Mkaaad W.. VS. Ftsli anstd Wlifiife Service. San FEHKUCoBay National Wildlife Refuge, P.O. Box 5M, NewriL California 94560 PMosh, tL, Ziodits^ OepattmeoL University of Box 351800. Sealde. Washin^toa Scaly. Spencer G_ Departmenl of Zoolog\'. Univeraty of Manitoba. Winnipeg. Manitoba R3T 2N2 C.anada Sowls. Aniiiir L_ U.S- Fisb and Wildlife Senice. Alaska Mariliime Refiige, 2355 Kiuiiemak Bay Drive, HcBBcc Alaska 99603. UiqTublished survey archive ' photographs, counts of individual birds were made and. in lower-quality photographs, blocks of 10. 50. or 100 birds were counted. Photographs were occasionally supplemented with visual estimates. Small numbers of munes were flushed from colonies by low-flying aircraft. Aerial photographic surveys of murre colonies were improved and better standardized from 1985 to 1995 by the USFWS. National Biological Service. U.S. Geological Survey, and Humboldt State University (Takekawa et al. 1990: Carter et al. 1992. 1995. 19%. 2000: Sydeman et al. 1997: McChesney et al. 1998. 1999: see Tables A- 1 and A-2). In general, counts were considered to be comparable at most colonies from 1 979 to 1995. However, notable exceptions were Castle Rock in 1979-82 and Point Reyes in 1979-81. Since 1985. all central California colonies have been surveyed using either a high-wing, twin-engine Partanavia (or a Cessna 337 aircraft). At the South Farallon Islands, colonies were surveyed from about 1 83 to 274 m (600 to 900 feet) and others from about 122 to 213 m (400 to 700 feet). Northern California colonies were sur\eyed at altitudes of 122 to 213 m (400 to 700 feet) using a single-engine Cessna 150 or 182 (1985-90) or a high-wing, twin-engine Partanavia (1993-95). In most years, colonies were surveyed once in late May or early June (i.e., near the end of egg laying and before colony departure). During this period, murre numbers are high and least variable (Takekawa et al. 1990). On rare occasions, small numbers of murres were flushed from colonies and surveys were continued at higher altitudes. At the South Farallon Islands. sur\'eys were conducted Rgure A-1 . Aerial photography was conducted wHti hand-held cameras from helicopters in Oregon and Washington, and from fixed-wing aircraft in (^lifomia. In this photo. R. W. Lowe is taking photographs from a helicopter at Three Arch Rocks, Oregon (Photo by D. S. Pitkin). 88 USGS/BRD/ITR-2000-0012 Table A-1. Summary of aerial photographic surveys of common murre colonies in central California, 1 979-1 995." Year Dates Field personnel Sources 1979 7, 1 1 June Sowls, Nelson, Lester, Rodstrom Sowls etal. 1980 1980 24 June Sowls, DeGange, Nelson, Lester, Stewart Sowls etal. 1980 1980 5-7 May Briggs, Lewis, Tyler Briggs etal. 1983 13 July Briggs, Lewis, Tyler Briggs etal. 1983 1981 19-21 May Briggs, Lewis, Tyler Briggs etal. 1983 30 June-2 July Briggs, Lewis, Tyler Briggs etal. 1983 1982 1-3, 19 May Briggs, Lewis, Tyler Briggs etal. 1983 28-30 June Briggs, Lewis, Tyler Briggs etal. 1983 1985 30 May; 12 June Lowe, Boekelheide Takekawa etal. 1990 1986 4-5 June Harvey, Penniman Takekawa etal. 1990 1987 26-27 May Harvey, Takekawa Carter etal. 2000 1988 23-24 May Takekawa, Accurso, Foerster Carter etal. 2000 1989 23-24 May Takekawa, Accurso, Carter Carter etal. 1992 1990 29-30 May Takekawa, Carter, Albertson, Roster Carter etal. 2000 1993 27-28 May Takekawa, Carter, Gilardi, Rauzon Carter etal. 1996 1994 4, 8 June Takekawa, Carter, Parker Carter etal. 1996 1995 30 May; 1-2, 14, Takekawa, Carter, Parker, McChesney, Carter etal. 1996 20 June Carter, Mclver, Keeney 'See Appendixes C and D Table A-2. Summary of aerial photographic surveys of common murre colonies in northern California, 1 979-1 995.' Year Dates Field personnel Sources 1979 15 May; 19 June 12 & 24 July; 2 August Sowls, Nelson, Lester, Rodstrom Sowls etal. 1980 1980 9, 23, & 25 July Sowls, DeGange, Nelson, Lester, Rodstrom Sowls etal. 1980 1980 5-7 May Briggs, Lewis, Tyler Briggs etal. 1983 1-3 July Briggs, Lewis, Tyler Briggs etal. 1983 1981 19-21 May Briggs, Lewis, Tyler Briggs etal. 1983 30 June-2 July Briggs, Lewis, Tyler Briggs etal. 1983 1982 1-3,19 May Briggs, Lewis, Tyler Briggs etal. 1983 28-30 June Briggs, Lewis, TVler Briggs etal. 1983 1985 5 June Lowe Carter & Takekawa*" 1986 19 June Takekawa, Nelson Takekawa etal. 1 990 1987 1 June Takekawa, Nelson Carter & Takekawa*" 1988 19 May Takekawa, Nelson Carter & Takekawa*" 1989 30-31 May; 16 June Takekawa, Nelson, Carter Carteret al. 1992 1990 6, 8 June Takekawa. Nelson Carter & Takekawa" 1993 8-9 June Takekawa, Carter, Carter Carteret al. 1996 1994 8, 13-14 June Takekawa, Strong. Strong Carteret al. 1996 1995 5-7 June Takekawa, Carter. Parker, Strong Carteret al. 1996 'See Appendixes C and D "Unpublished data at higher altitudes and farther from shore to prevent flushing. Entire colonies were photographed by two (one front-seat and one back-seat) photographers between 1000 and 1400 h (PDT), using 35-mm cameras with 300-mm lens. Each part of a colony was passed over several times to ensure photograph quality and overlapping coverage of all breeding areas. Close-up slides of each part of the colony from either photographer were pieced together using separate overview photographs taken only by the front-seat photographer using a 50-mm lens. Slides were then projected on white paper and each murre was counted (Figure A-2). After obtaining direct whole-colony counts of murres from aerial photographs, a k correction factor can be used to estimate the total number of breeding birds using the colony in the survey year. Based on counts of murres and egg-laying sites in a plot on Upper Shubrick Point on the South Farallon Islands, California, BIOLOGY AND CONSERVATION OF THE COMMON MURRE 89 the it, correction factor is calculated using the formula k^(t^) = n^(2)/n (/, ) where n^ = number of plot sites where an egg was laid that season, which is then multiplied by two breeding birds/site, and n^ = the number of murres counted at time t. This calculation differs slightly from it as described by Birkhead and Nettleship ( 1 980), which calculates number of breeding pairs. Alternatively, a it, correction factor also has been used where n^ equals the number of egg-laying sites on the survey day (Takekawa et al. 1990). Whereas little difference exists between these versions of it at the South Farallon Islands (Sydeman et al. 1997). the it^ calculation is preferred overall because it prevents possible biases relative to the timing of the survey. Annual it values can be determined by averaging counts from different days. Since 1979. various it, and it, values have been used to adjust whole-colony counts to estimate the number of breeding adults at colonies, which then can be summed to estimate the breeding population in California. A general it correction factor of 1 .67 was used to adjust whole-colony counts in 1979-82 (Sowls et al. 1980; Briggs et al. 1983) based on data from the South Farallon Islands in the early 1970s (Ainley 1976. and personal communication). Takekawa et al. (1990) calculated an average it, value of 1.68 by averaging four years of data from 1980 to 1986. This average value was applied to all colonies since 1980. except at the South and North Farallon Islands where annual values were applied. Carter et al. (1992) also used this it, value of 1.68 to estimate colony size at all colonies in 1989. except at the Farallon Islands where an aimual 1989 value was used. More details about it correction factors developed at the South Farallon Islands are available elsewhere (Boekelheide et al. 1990; Takekawa et al. 1990; Carter et al. 1992). Sydeman et al. (1997) reevaluated and corrected all data fipom 1985 to 1995 and calculated /t, values that averaged 1.67 with relatively Uttle variation among years. Takekawa et al. (1990) reported the general accuracy of estimates of breeding adults at colonies in California to be within 10%. However, further work is required to better determine error associated with these estimates. Oregon Murre colonies in Oregon were censused fipom 1 966 to 1975 by USFWS biologists using fixed- wing aircraft. These aerial censuses were generally flown in late June or early July and relied on visual estimation, rather than aerial photography, to determine the number of murres present. This method often resulted in underestimation, esjjecially at larger colonies; 1974—75 estimates of colony size were probably low. Aerial photographic surveys were first used in 1979 during the first coastwide survey of nesting seabirds in Oregon (Varoujean and Pitman 1980). However, many of the photographs were taken too late in the season to provide accurate counts and the population estimate was low. In late June 1989. Ecological Consulting Incorporated conducted murre colony counts in Oregon (Briggs et al. 1 992 ). The focus of their research was to conduct offshore and coastal strip transects surveys of marine mammals and seabirds using a ilxed-wing aircraft. On June 27 and 28. they made a nonstandardized aerial survey of murre colonies and counted murres at coastal locations using visual estimates from aircraft Rgure A-2. Aerial photographs were projected onto a wall with white sheets of paper, best photographs were selected for counting, and then each murre was marked on the paper. In this photo, the best close-up photographs of Tillamook Rock, Oregon, have been pieced togettier. and mun-es on different parts of itie rock ace being marked (Photo by D. S. Pitkin). 90 USGS/BRD/ITR-2000-0012 traveling at 185 km/h parallel to shore (i.e., 0.4 km from shore at altitudes of 60-300 m). Photographs were taken of all aggregations of more than 10 birds and later were inspected to verify visual estimates. Nonstandardized techniques were used because of permit restrictions near murre and other seabird colonies and probably resulted in less accurate whole-colony counts of murres (K. T. Briggs and R. G. Ford, personal communication). The uncorrected count was 262,364 birds (Briggs et al. 1 992). Data obtained by Ecological Consulting Incorporated were considered inaccurate and were not used for trend analyses in Chapter 2 because (1) nonstandardized survey techniques were used; (2) the survey did not include 29 (42%; n = 69) active murre colonies in Oregon in 1989, especially some large colonies exceeding 10,000 birds; (3) some counts were reported for rocks where murre colonies were not present; and (4) counts for many colonies were lumped together as a single count. Large discrepancies exist where 1989 standardized counts by the USFWS (7 and 9 June) can be compared with those of Briggs et al. (1992). At eight sites compared, the Briggs et al. survey reported greater numbers at three colonies (range, 5-45%) and significantly lower numbers at the other five colonies (range, 49-98%) than the USFWS survey. Since 1988, single annual surveys of all major murre colonies in Oregon have been conducted (except 1995; Table A-3) using standardized techniques. Surveys were flown in early June to coincide with late incubation and hatching (after Takekawa et al. 1990). Surveys were conducted using a Hughes 500 (models D & E) helicopter at altitudes of 260-330 m with both right- side doors removed. The five-bladed propeller configuration reduces noise and lessens possible disturbance. On rare occasions, small numbers of murres have flushed from rocks. These birds are typically on the edges of the colony and probably involve prospecting or roosting birds, but the numbers are recorded and included in the colony count. Colony photographs were taken by two photographers using 35-mm cameras with 100-300- or 300-mm lenses for close-up photographs (front-seat photographers) using ASA 400 color slide film and shutter speeds of 1/500 or 1/1000 per sec, and 55- or 70-2 10-mm lenses for colony overviews (back-seat photographer). Overlapping colony slides were projected onto large sheets of paper, simultaneously using 3-4 projectors and individual birds were counted. A general k correction factor of 1 .67 (based on California data) was applied to all count data to estimate the number of breeding adults at colonies in Oregon. No study has calculated a k specific to Oregon colonies. The first trial of this photographic survey method was conducted along the southern Oregon coast in June 1986. The survey was expanded to the entire Oregon coast in 1987, though not all colonies were counted. From 1988 to 1995, all major murre colonies in Oregon were photographed annually. In 1995, three replicate aerial photographic surveys were conducted at a subset of Oregon colonies. These surveys were conducted at 15 north coast study sites both 2 weeks before and 2 weeks after the standard June survey (i.e., 23 May, 7 June, and 21 June) to examine the validity of using a single survey as a general measure of peak numbers of murres at colonies. The results showed considerable variation in the number of birds present at some specific colony sites. However, overall numbers of birds recorded in each survey were similar. On 23 May and 2 1 June, 1 .3% more and 2.5% less birds were recorded, respectively, compared with the standard survey on 7 June. The mean total of birds recorded for the three surveys was only 0.4% less than the total for the standard early June survey. The results indicated that, at least in 1995, the single standard survey in early June was sufficient and accurate enough for population monitoring and trend analyses. Washington Murre colonies in Washington were aerially surveyed each year in late June or early July from 1 979 to 1995 (Table A-3). This later timing of surveys reflected a later timing of breeding (Manuwal and Carter 2001) and greater stability of numbers of murres on colonies after May (Speich et al. 1987; Parrish 1995). For the 1979-83 period, a single, annual survey was flown with a Cessna 172 or 182 at an altitude of 170- 230 m and murres were counted later from aerial photographic slides. Since 1983, all surveys were conducted with a Hughes 500 D helicopter at an elevation of 70-250 m (with the passenger door removed). Murres were counted with a hand-held tally counter and binoculars, except in 1987, 1994, and 1995 when birds were photographed and later counted from slides. Direct counts were considered acceptable because of the small numbers of birds attending most colonies. Census data were obtained during single helicopter flights through 1993. Two flights were conducted in 1994 and four replicate flights in 1995. During fixed- wing surveys, it was possible to count only the major murre colonies, whereas the helicopter allowed surveys of all sites, except the Tatoosh complex. This complex has been surveyed by the USFWS only since 1994. Surveys were flown between 0930 and 1400 h (PDT) during late June or early July. During multiple survey years, surveys were conducted between mid- June and BIOLOGY AND CONSERVATION OF THE COMMON MURRE 91 Table A-3. Summary of aerial photographic surveys of common murre colonies in Oregon and Washington, 197&-1995.' Year Dates Reld personnel Sources Lowe^ Lowe*" Lowe* Lowe* Lowe* Lowe* Lowe* Lowe* Lowe* Lowe* Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson 1991 Wilson* Wilson* Wilson* Wilson* WUson* Oregon 1986 25 June; 3 July Lowe. Boone. Brown 1987 25-26 June Lowe. Anderson 1988 3-4 June Lowe, Anderson 1989 7, 9 June Lowe, Naughton 1990 11. 14 June Lowe. Naughton 1991 4, 5 June Lowe. Naughton 1992 2, 4 June Lowe, Reimer 1993 8, 24 June Lowe, Pitkin 1994 8, 10 June Lowe, Pitkin 1995 23 May; 7. 21 June Lowe, Pitkin Washington 1979 5 July Wilson 1980 2 July Wilson 1981 29 June Wilson 1982 17 July Wilson 1983 2 July Wilson 1984 6 July Wilson 1985 26 June WUson 1986 20 June Wilson 1987 30 June Wilson 1988 3, 5 July Wilson 1989 22 June Wilson 1990 23 June Wilson 1991 8, 16 July Wilson 1992 6 July WUson 1993 29 June Wilson 1994 16 June; 5 July WUson 1995 19, 25 June; 13. 27 July Wilson 'See Appendixes E. F. and G "Unpublished data late July. The time of day and time of the breeding season when surveys were conducted roughly matched methodology in California, but survey dates were later due to the later breeding phenology in this area. During 1 979-94, photographs were taken with a 35-nmi camera and a 135-mm lens. In 1995, the colonies were photographed with a 70-200-mm lens. Only Kodak Ektachrome 400 ASA film was used. Counting murres from slides involved projecting the transparencies onto a paper flip chart. Small groups of mumes (less than 30) were circled and then counted with a tally counter. This process was repeated until the entire colony was counted. When murres were densely packed, or with poor slide resolution, the number of birds within small groups was estimated. A general k correction factor of 1 .67 (based on California data) was applied to all count data to estimate the number of breeding adults at colonies. No study has calculated a k specific to Washington colonies. As in Oregon (see above). Ecological Consulting Incorporated conducted murre colony counts in Washington in late June 1989 (Briggs et al. 1992). On June 27 and 28. they made a nonstandardized aerial survey of murre colonies using visual estimation and aerial photography. The uncorrected total was 12,810 birds, with 830 at Tatoosh Island (Briggs et al. 1992). On 22 June, USFWS personnel counted 3,925 birds (excluding Tatoosh Island: see Appendix F). Data obtained by Ecological Consulting Incorporated were considered inaccurate and were not used for trend analyses in Chapter 2 because (1) nonstandardized survey techniques were used, (2) the survey did not include some active murre colonies in Washington in 1989, (3) some counts were reported for rocks where murre colonies were not present, and (4) counts for many colonies were lumped together as a single count. Where 1989 standardized counts by the USFWS can be compared with those of Briggs et al. (1992), there are 92 USGS/BRD/ITR-2000-0012 large discrepancies. At six sites compared. Ecological Consulting Incorporated reported much greater numbers at three sites (range, 280-7630%), much lower numbers at one site (750%), and hundreds of murres at two sites (not colonies) where USFWS surveys found none. Differences between surveys were so large that other factors also may have been involved (e.g., colony misidentifications, extensive variation in numbers of murres attending colonies, or possible colony disturbances). British Columbia The only large murre colony in British Columbia is at Triangle Island. In 1989, an extensive study was undertaken to provide the only reliable and complete estimate to date (Rodway 1 990). This study used ground photographs, telescope counts, and boat counts to provide complete coverage of the colony and used breeding phenology, attendance patterns, and A: correction factors from several plots in the colony to estimate the 1989 colony size (P) using the formula P - k (Tr + C) where k - ratio of breeding sites to total birds present on study areas (i.e., equivalent to a it correction factor), T = total mean count from photographs of the colony, r = ratio of telescope to photographic counts on the study plot; and C = count from the top of Puffin Rock of birds that were obscured from the water. In 1989, Rodway (1990) calculated a mean k value of 0.41 (range, 0.39-0.53) using the formula presented in Birkhead and Nettleship (1980). This value is comparable to a k^ correction factor value of 0.82, using the equation presented under California methods. Rodway (1990) noted that his k value was much lower than that reported for other Pacific and Atlantic colonies. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 93 Appendix B Histories of common murre (Uria aalge californica) colonies in California, 1800-1978 (prepared by H. R. Carter) As part of the assessment of the status of common murres (Uria aalge californica) in California, it is important to appreciate the long history of human influences on colonies and birds at sea in this area. Current conservation problems cannot be fully assessed and conservation actions to best restore colonies or populations cannot be fully conceived or implemented without a reasonable concept of the original size and distribution of the murre population. The known histories of most murre colonies in California have not been summarized previously, even though the history of the South Farallon Island colony has been described by early naturalists and others in some detail (e.g., Ainley and Lewis 1974) and the extirpated colony at Prince Island has been well documented (Huntet al. 1979). For other murre colonies, information before 1 969-70 (when murre colonies were first inventoried collectively in California [Osborne and Reynolds 1971; Osborne 1972]) was poorly recorded and poorly known. In addition, little information was obtained in the 1970s before the advent of more frequent monitoring of murre colonies in 1979 (Sowls et al. 1980). In their major summary of historical data on the birds of California, Grinnell and Miller (1944) listed only five colonies in central and southern California; three active colonies (South Farallon Islands, Point Reyes, Point Resistance [i.e., mouth of Bear Valley] and two extirpated colonies at San Pedro Rock and Prince Island (Santa Barbara County). They also noted Dawson's (1923) report of murres breeding on rocks of Humboldt and Del Norte Counties but did not provide further details. Many murre colonies were known much earlier than available sources would indicate. In this summary, I collated information from previous summaries and reported on substantial new information from more obscure published and unpublished sources to provide a more detailed summary of historical information. I also included a more extensive presentation of historical material for the South Farallon Islands than found in previous sources. For colonies other than the South Farallon Islands, unpublished information and egg records in museum collections (see Methods) have been especially enlightening. Although doubtless incomplete, this summary provides much additional historical information not found in other summaries to date, especially for central California colonies. Partial summaries of conservation problems of murres in California prior to 1978 are found in several sources (Osborne 1972; Ainley and Lewis 1974; Hunt et al. 1979; Sowls et al. 1980; Carter 1986; Ainley and Boekelheide 1990; Takekawa et al. 1990; Sydeman et al. 1997). Here, I focused on summarizing information on direct impacts to murre colonies from exploitation, visitation, or disturbance. Other less direct problems (e.g., oil and gill-net deaths) will be discussed in greater detail elsewhere in this assessment (Chapter 3). My approach to summarizing historical information on murres involved the following considerations: (1) revisiting all original sources cited by previous authors, except where noted; (2) including literature and unpublished information to allow the reader better access to all available knowledge; (3) reporting information as directly as possible from sources with few judgements about the quality of information, except where noted and where additional information was provided with which the reader could make some judgements; (4) using unpublished field notes of Charies Clay, Laidlaw Williams, and Howard Cogswell (other existing field notes were unobtainable, not easily available, or not known); and (5) summarizing (historical) human activities that probably affected murre colonies, especially where the colonies were poorly documented. Due to the variation between the type and amount of information available from each source, I chose not to use a shorter and more convenient tabular format for presenting information that would not allow adequate presentation of available information. Although much new information is made available here, this summary is incomplete and future efforts may uncover additional information. Farallon Islands Summary The South Farallon Islands are the type locality for the "California murre" (U. a. californica) and another old name is the "Farallone Bird" (Coues 1903; Dawson 1923). Much information on breeding murres at the South Farallon Islands has been documented (Ainley and Lewis 1974; Doughty 1974; Carter 1986; Takekawa et al. 1990; White 1995). This colony probably once was the largest colony for the common murre in California, Oregon, Washington, and British 94 USGS/BRD/ITR-2000-0012 Columbia (and perhaps the world) but was all but destroyed by the 1930s because of human occupation and commercial egging in the nineteenth century and oil pollution in the early twentieth century. However, from 1 950 to 1 982, the colony grew from a few thousand to over 100,000 breeding birds. Then, in the 1980s, this colony and others in the central California population suffered heavily from gill-net and oil-spill mortalities and declined significantly (Carter 1986; Ainley and Boekelheide 1990; Takekawa et al. 1990). The history of the murre colony at the South Farallon Islands is relatively well documented, although the North Farallon Islands are among the least known colonies. Below, I review the history of Farallon murre colonies in detail because breeding biology and colony trends at the South Farallon Islands have been well studied in recent years and are often cited without reference to the extensive historical impacts this colony has undergone or the amount of information available on the size and status of the colony during certain historical periods. In particular, estimates of colony size before 1979 are not directly comparable to more recent estimates. Russian American Fur Company (1812-1838) The earliest reported landing on the South Farallon Islands was by Sir Francis Drake aboard the Golden Hind in 1579 when the ship stopped on 23-24 July to collect seal meat and seabirds for food (Hoover 1952; White 1995). In 1807, the Boston sealing ship O'Cain visited the Farallon Islands and vast numbers of marine mammals were noted (Bancroft 1886; Doughty 1974; White 1995). From 1810 to 1812, several sealing visits were made by American sealers. From 1 8 1 2 to 1 838, the Russian American Fur Company, in business with American sealers, operated a sealing station at the South Farallon Islands staffed by native people from Alaska and California who mainly harvested fur seals {Callorhinus ursinus), elephant seals (Mirounga augustirostris), and sea lions (Bancroft 1886; White 1995). In 1817, about 30 people lived on the islands. After 1818, seal numbers were much lower but people remained to kill sea lions and birds and to collect eggs. Annually, from 5,000 to 10,000 "gulls and other birds" or "sea ducks" (probably murres) were killed and the meat was dried for food (Bancroft 1886; Khlebnikov 1976). In 1828, 50,000 birds were killed and 3,61 1 lbs (1,638 kg) of meat were obtained from these birds (Khlebnikov 1976). Harvest also occurred on the North Farallon Islands where Russians and "Kadiaks" were noted in May 1825 (Bancroft 1886). Feathers and meat were sent to the main Russian establishment in California at Fort Ross, Sonoma County. In 1827 and 1 828, respectively, nine and 1 1 inflated skins of marine mammals filled with 1,083 and 1,192 lbs (4,423 and 5,405 kg) of feathers were sent to Fort Ross; "a good many eggs" also were collected and used for subsistence on the islands, shipped to Fort Ross, and exported to Alaska (Khlebnikov 1976; Essig et al. 1991). At this time, about 30 people still lived on the islands. Egging probably occurred from the earliest days of the sealing station. In 1819, Chichinoff (Hoover 1952; Hillinger 1958) noted subsistence harvesting of seabird eggs. In 1 825, Morrell (Hoover 1952; Hillinger 1958) noted that "Aquatic birds in considerable variety resort hither for purposes of laying and incubation, but the Russians seldom give them a chance for the latter process, generally securing eggs as fast as they are deposited." The Russians withdrew from the establishment at the Farallon Islands in 1838 and from Fort Ross in 1841. However, the extensive hunting of seabirds by the Russian American Fur Company over at least two decades must have caused a massive decline in the size of the murre colony, as well as that of many other seabird and marine mammal species. In addition, sporadic hunting continued on the islands during the 1840s (Bancroft 1 886) that probably continued to disrupt the colony, although at a lower level than previously. Farallone Egg Company and Murre Egging (1849-1881) Small-scale commercial egging was first conducted by "Doc" Robinson and O. Dorman in 1849 (White 1995; Brown 1999). Commercial egging began in earnest in 1850 by several different interests but eventually came under the sole control of the Pacific or Farallone Egg Company (Hutchings 1856; Scammon 1875; Greene 1892; Emerson 1904; Doughty 1971; White 1995). Eggs were supplied to bakeries and restaurants before the establishment of sufficient domestic poultry production for the rapidly expanding human population of the San Francisco area during the Gold Rush that began in 1 848. Between 3 and 4 million eggs (Hutchings 1856; Taylor 1895) had been brought to market since 1 850 (or an average of 428,57 1-57 1 ,429 eggs per year, based on my calculations). Heermann (1853) noted that "a trade (in eggs) is carried on with San Francisco, to the amount of thousands of dollars per annum," in 1853. Heermann (1859) reported that the annual value of eggs reached $ 1 00,000- 200,000, based on his 1853 visit. This profit seemed high to Palmer (1900), evidently because at the highest reported retail prices of $1.00-1.50 per dozen, profits should have been between $35,7 14 and 7 1 ,429 per year using Hutchings' (1856) reported harvest levels. However, Taylor ( 1 86 1 ) reported that egg prices in 1 849 BIOLOGY AND CONSERVATION OF THE COMMON MURRE 95 increased when sold away from the market and were as high as $6-9 per dozen. Nordhoff ( 1 874) reported that about 360,000 eggs were shipped in one season in the early years. Ainley and Lewis (1974) reported an estimate of about 400.000 breeding birds for 1 854 at the South Farallon Islands, based on an approximate 400,000 eggs removed per year and one egg laid per breeding pair per year (Ainley and Boekelheide 1990). This estimate should have been 800.000 breeding birds by my calculations without accounting for lost or broken eggs (i.e., 400.000 eggs with two adults per breeding pair and one egg laid per breeding pair per year). However, many eggs probably were replaced at least once. Therefore, 4(M),000 breeding birds may be reasonable, assuming an average of one replacement egg per first egg laid. On the other hand. Ayers reported over 500.000 eggs were harvested in 1854 on a limited portion of South Farallon Island and "'in the opinion of the eggers, not more than one egg in six of those deposited on that island was gathered" (Loomis 18%). This statement does not suggest careful accounting, eggers may have been "defending" their practice with such a statement, and few areas of the islands were inaccessible to eggers. As many as three million eggs could have been laid, which could correspond to a much higher colony size for the early 1 850s of at least 6 million breeding birds. Such an estimate assumes only one egg laid per breeding pair and includes eggs lost or destroyed before shipping. If one replacement egg per first egg was laid, then an estimate of 3 million breeding birds emerges. In my opinion, the historical colony size prior to European, Asian, and Alaskan contact in the early nineteenth century probably was between 1 and 3 million breeding birds. Major factors that I considered in arriving at this general estimate were ( 1 ) the lower end of the range — 1 million — should be much higher than the previous estimate of 400,000 breeding birds in the 1850s, given substantial reduction because of egging, hunting and other disruptions from 1812 to 1838; (2) insufficient information was provided in historical accounts to determine how many eggs — probably a substantial number — were not collected of those laid in the 1850s; and (3) the nature of historical information prevents determination of a more exact estimate within this range. It is unclear exactly how such large numbers of murres. other seabirds. and marine mammals shared available space at these islands. Earlier removal of marine mammals also may have benefitted murres by increasing available breeding space (D. G. Ainley. personal communication). After island visits in 1 862 and later. Gruber reported that 240.000-300,000 eggs were harvested for many years and first sold for S0.50 per dozen and later at $0.25-0.30 per dozen in the market at San Francisco (Gruber 1884; Grinnell 1926). However, it is unclear what years Gruber was referring to because the article was published in 1 884. By 1 872 and 1 873, respectively, 215,424 and 182,436 eggs were collected (Nordhoff 1874). Nordhoff (1874) determined that over 100,000 murres bred at the South Farallon Islands at this time by "allowing half a dozen to each murre, this would give nearly 36,000 [breeding pairs] . . . adding the proper number for eggs broken, destroyed by gulls, and not gathered . . ." Murre eggs were collected daily from May to July and thus were removed shortly after laying. Whereas murres were known or thought to continue laying after egg removal, it is unlikely that individual females laid 6-8 eggs as claimed by the egging company, and the murre colony probably was much larger than thought by Nordhoff. Eggs were sold for $0.26 per dozen in 1873 (Nordhoff 1874). Scammon ( 1 875) reported that 300.000 eggs were shipped to San Francisco each year and that eggs were gathered from the same breeding places only two or three times per season. Doughty ( 197 1 ) used Scammon"s 300,000 eggs each year as the annual harvest level from 1 857 to 1 87 1 . Nordhoff was assured by the manager of the egg company that there had been "no sensible decrease in the number of birds or eggs for twenty years" but fewer eggs in fact were being harvested by this time. By allowing some birxls to breed successfully at the end of the season, eggers had wrongly thought that they had ensured adequate production of murres to continue the egging business. From 1874 to 1883, about 180,000 eggs were harvested aiuiually (Emerson 1904). Commercial egging by the Farallone Egg Company ended in 1881 when company workers were removed from the island by a U.S. Marshall and soldiers because of difficulties with the lighthouse keepers and a long- term dispute over company egging rights with the federal government. A lighthouse had been erected in 1853 and the islands had been reserved for lighthouse purposes in 1851, a fact further substantiated by President Buchanan in 1859 after a legal challenge (Doughty 1971; White 1995). Continued Egging and Other Human Impacts on the Farallon Islands (1882-1904) Egging by Ughthouse keepers and Greek and ItaUan fishermen continued beyond 1881 (Bryant 1888; Blankenship and Keeler 1892; Greene 1892). Greek and Italian immigrants formed much of the local fishing community in San Francisco at this time (Daskarolis 1 98 1 ). The retail price of eggs had fallen to $0. 1 2-0.25 per dozen (Bryant 1888; Greene 1892). In 1884,300.000 eggs were harxested and between 180,(X)0 and 228,0(X) 96 USGS/BRD/ITR-2000-0012 eggs were harvested in 1885-86 (Bryant 1888, Palmer 1900). In 1 887, 300,000 eggs were collected, the largest harvest in several years (Emerson 1904). Greene (1892) noted that close to 1 80,000 eggs were harvested in 1 892. Emerson (1904) reported similar annual harvests from 1 888 to 1 895. By July 1 896, 9 1 ,740 eggs were harvested and the retail price had dropped to $0,125 per dozen. Extensive egging at the North Farallon Islands also occurred in 1896 and the "crop was said to be larger than that of South Farallon" (Loomis 1896). Bryant (1888) had first reported murres breeding on the North Farallon Islands although it had been known much earlier that seabirds bred there in large numbers. In fact, egging may have occurred there in 1 863 (Brown 1 999). In early July 1 899, at least 23 eggs were collected by fishermen at the North Farallon Islands and obtained by D. A. Cohen for his egg collection; eight of these eggs are currently housed in the collection at the Western Foundation of Vertebrate Zoology (WFVZ) , Camarillo, California (WFVZ Nos. 117,672-117,679). Loomis encouraged the American Ornithologists' Union and the California Academy of Sciences to take actions to protect the murres and other seabirds (Dutcher 1897; White 1995). The Lighthouse Board responded to a letter from the American Ornithologists' Union and prohibited egging by lighthouse keepers and all others at the Farallon Islands in November or December 1 896 (Anonymous 1897; Dutcher 1898; Palmer 1900). Despite protection, Emerson (1904) noted the loss of several murre breeding areas on the South Farallon Islands between 1887 and 1903 and considered that "a great decrease in the laying of the murres had taken place on South Farallone, and I was prepared to note a corresponding change in the abundance of murres." Illegal egging continued, although at lower levels, until at least 1904 (Lastreto 1930; Doughty 1971; White 1995). Additional evidence of continued egging is found in the WFVZ collection. On 22 June 1897, W. E. Snyder obtained at least one egg (set number 72) that had been "collected by market eggers" (WFVZ No. 692). On 8 July 1 898, D. De Groot bought at least five eggs (set numbers 3-7) "in the San Francisco market" (WFVZ Nos. 45,808-45, 810; 45,812-45,813). On 28 June 1901, J. Mailliard of San Francisco purchased at least four eggs (set numbers 2-5) "in market" (WFVZ No. 112,939). In addition to egging, continual human occupation of the South Farallon Islands since 1853 probably contributed to a decline in the size of the murre colony because of breeding habitat changes and disturbance from island personnel, children, dogs, cats, and livestock. Island habitats were changed by the construction of numerous rock walls (e.g., pathways to and foundation for the lighthouse, the "Farallon Railroad" bed, various rock walls around buildings and cisterns) and buildings (e.g., egg storage areas, the original lighthouse keepers' "Stone House") using rocks collected from around the island, especially from breeding slopes on Lighthouse Hill where rocks are abundant. Such rock-wall building construcfion continued until about 1905 when the current "Carpenter's Shop" was constructed (P. White, personal communication). Guano harvesting also occurred (Barlow 1897). The human population numbered at least 20 people in 1898 (White 1995), and the loss of breeding areas above the lighthouse keeper houses and other areas, noticed between 1 887 and 1 903 (Emerson 1904) and later, probably resulted in some degree from human disturbance (Dawson 1923). In fact, many breeding areas probably were lost well before 1887. Weather stations were built near murre breeding areas and staffed by additional personnel in 1902 near Jordan Channel and in 1905 near Shubrick Point (P. White, personal communication). These stations resulted in greater human access to West End Island (involving a walking bridge) and the Shubrick Point area of Southeast Farallon Island. However, many thousands of murres were still noted in 1903-04 (Emerson 1904; Ray 1904). Human Impacts on the Farallon Islands in the Early Twentieth Century In addition to the impacts of oil pollution on the murre colony (Chapter 3), island personnel and facilities continued to expand at the South Farallon Islands. During World War I, 26 Marines were stationed on the island and a naval radio compass station continued to operate after the war. During World War II, the island population had grown to 78 people, although only 17 people remained by 1953 (White 1995). One positive action taken during the early twentieth century was the creation in 1909 of the Farallon Reservation, which was to be "a preserve and breeding ground for native birds" (White 1995). This reservation, however, only protected colonies on the North Farallon Islands (i.e., the South Farallon Islands were not added until 1969, see later). It is not known why President Roosevelt took this action but it presumably was related to heavy impacts to murre colonies at both the South and North Farallon Islands noted by Loomis (1896), previous efforts to stop egging at the South Farallon Islands, and increasing efforts to protect wild birds in the United States. In particular, earlier efforts by W. L. Finley, W. L. Dawson, and others to protect seabird colonies in Oregon and Washington undoubtedly influenced Roosevelt's decision to establish national wildlife refuges. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 97 Murre Colony Sizes (191 1-1950) From 1911 to 1950. murres were not recorded breeding at the South Farallon Islands in large numbers. Only a few hundred to a few thousand murres probably bred there during much of this period. By 191 1, fewer than 20,000 murres were estimated at the South Farallon Islands (Dawson 1911). Egg collectors frequently obtained eggs from the South Farallon Islands from 1859 to 1913, based on hundreds of egg specimens collected during this period in collections at: WFVZ: Santa Barbara Museum of Natural History (SBNHM), Santa Barbara, California; University of California Museum of Vertebrate Zoology (BMVZ). Berkeley, California: National Museum of Natural History (USNM), Smithsonian Instimtion, Washington. D.C.: and Harvard University Museum of Comparative Zoology (MCZ). Cambridge. Massachusetts. I did not present details for these Farallon-collected eggs in this appendix because the history of egging and other visits by ornithologists are well told with other information above. No eggs in these collections were obtained after this period. On 20 August 1922, murres were considered to be less numerous than in 1917 although some birds may have fledged by this date (Allen 1922; Kibbe 1922). However, murres may have regularly bred that late in the year because of effects from egging when breeding often extended into September (Bryant 1888), although 1859-1913 egg specimen dates ranged between 1 0 May 1 890 (USNM B3423 1 ) and 28 July 1 886 (WFVZ 460 1 6), with most collected in June. In June 1923, Chaney (1924) reported only tens of murres breeding in three small groups in protected crevices. On 24 August 1930, only five murres were found at the island, which may have reflected near extermination and earlier breeding by small numbers since some birds were observed at sea with chicks (Anonymous 1930: Lastreto 1930). However, the lighthouse keeper indicated that murres had been depopulated by about 999c (since Knuder had come to the Farallones in 1915 [White 1995]): this decline was related to past egging practices and oil pollution but remaining smaller numbers of murres were falling prey to western gulls (Lams occidentalis: Allen 1 930; Knuder 1930; Lastreto 1930; Brooks 1937). In August 1933. Smith (1934) observed only three young in protected crevices but noted that the main colony probably had finished breeding earlier. Smith also noted that strict protection of breeding areas was occurring and no one was permitted to travel to West End Island from 15 April to 15 August Murre Colony Sizes (1950- 1968) On 22 May 1 955, about 2.000 murres were reported within 3.2 km (2 miles) of the islands but it was unclear how many were on shore. On 30 April and 22 May 1 955. thousands were reported on the island and on the water around the island (H. Cogswell, unpublished field notes; Cogswell 1955; Cogswell and Fray 1955a). On 28 April 1956, Cogswell noted about 1 .000 murres at and around the island, including 600 on die island. On 27 May 1 956. he reported 300 murres at the island, and hundreds also were reported on 3 June 1956 at the island (Cogswell and Stallcup 1956; H. Cogswell, unpublished field notes). On 10-17 June 1958, Bowman (1961) conducted an on-island survey of the South Farallon Islands and determined about 2,000 birds attending eggs. He mapped breeding areas and noted small groups of 5-20 birds breeding in caves and on ledges at several points. The largest groups were on the westernmost parts of West End Island (Great Arch. Phil's Hill, and Indian Head) and on Sugarloaf and Aulon Islet. Smaller numbers bred at Southeast Farallon Island (Shubrick Point. Great Murre Cave. Shubrick Cove, and Fertilizer Flat). Saddle Rock, the Islets (Arch Rock. Finger Rock, and Sealion islets), and other parts of West End Island (Maintop, Pelican Bowl, and West End Cove). Thoreson (1959) reported a direct count of 6,718 murres and a range of 6,000-7,000 birds at the South Farallon Islands in June-August 1959. Most birds were counted at the Islets (2,000) and West End Island (3.500). Bowman's and Thoreson's estimates seem to be the first well documented numbers of breeding birds on the South Farallon Islands but also may reflect lower breeding effort during El Nino conditions in 1957-59 (Lenarz et al. 1995). On 3 April 1960. murres and pigeon guillemots (Cepphus columba) were reported as abundant at the island (Albertson I960). D. Bleitz (unpublished field notes) noted concentrated small colonies on high steep- walled pinnacles on 4 August 1961. On 19 April 1962. thousands were reported on or near the island (H. Cogswell, unpublished field notes). On 3 1 March 1963, thousands of murres and other species were noted at the island (Paxton 1963). On 31 May 1964. murres and other species were "ubiquitous" at the main island (Paxton 1964). Pinney (1965) mapped locations where murres bred on Southeast Farallon Island in 1961-64, including Shubrick Point, Great Murre Cave, Shubrick Cove. Fertilizer Flat. Tower Point, and Elephant Seal Blind Point. On 23 April 1966. hundreds of murres flew from the rocks (Stallcup and Chandik 1966) and H. Cogswell (unpublished field notes, American Birds Files; Chase and Chandik 1966) reported several thousand on the island and noted that the "population felt to be decidedly larger than 8-10 years previously." On 14 June 1967. a rough estimate of 500 murres at Shubrick Point was made from land (H. Cogswell, unpublished field notes). During summer 1968, low- 98 USGS/BRD/ITR-2000-0012 flying jet aircraft caused extensive flushing of murre colonies (Speich et al. 1987). Lessened Human Impacts and Murre Colony Sizes (1969-1978) In 1969, the South Farallon Islands were included, along with the North Farallon Islands, in the Farallon National Wildlife Refuge, under the management of the U.S. Fish and Wildlife Service (USFWS). Osborne ( 1 969) reported only 200 breeding pairs in July-August 1969, although surveys probably were conducted too late in the season. H. Cogswell (unpublished field notes) estimated 2,000 murres on the island or flying around it on 29 April 1970; however, numbers "increased from 4,000 to 6,000 during April and May" (Baldridge et al. 1970a,b). Osborne and Reynolds ( 1 97 1 ) reported 5,000 breeding pairs at the South Farallon Islands in 1970. In 1 97 1 , the Point Reyes Bird Observatory was contracted by the USFWS to protect and monitor wildlife at the Farallon Islands. In 1 974, all U.S. Coast Guard personnel left the island. For the first time since the early nineteenth century, human disturbance by island personnel was reduced to minimal levels, including newly designated off-limit areas on Southeast Farallon Island. West End Island and the North Farallon Islands were designated as National Wilderness Areas. Ainley and Lewis (1974) reported 20,5(X) breeding birds at the South Farallon Islands in 1972 (based on detailed on-island ground counts but without a k correction factor). This 1972 estimate represented a large increase in the size of the murre colony since 1959 but the 1972 survey probably constituted a more careful survey than any conducted previously, as well as documenting breeding during an El Nino. Piatt et al. (1991) noted that if the 1972 survey was adjusted with a k correction factor and adjusted roughly for comparability with more recent aerial survey estimates (since 1 979) and possible lower breeding effort during 1972-73 El Nifio conditions (Lenarz et al. 1995), about 45,000 breeding birds could have laid eggs in 1972. H. Cogswell (unpublished field notes), from a boat, reported only 1 2,000 murres on Southeast Farallon Island (plus several hundred on Seal Rock) on 30 April, suggesting differences between counting techniques. On 22 April 1973, H. Cogswell (unpublished field notes) reported several thousand at the island. No other detailed surveys of the numbers of breeding murres were conducted at the South Farallon Islands until 1979 when annual ground and boat surveys began (Ainley and Boekelheide 1990; Takekawa et al. 1990; Sydeman et al. 1997). However, rough estimates of the numbers of breeding pairs in 1 975-79 were reported by Point Reyes Bird Observatory to the USFWS, respectively, as 14,000, 14,000, 20,000, 25,000, and 30,000 (U.S. Fish and Wildlife Service 1980). Ainley and Whin (1974) reported a 1972 estimate of 14,000 breeding pairs for San Francisco County. This value included the South Farallon Islands surveyed in 1972 (Ainley and Lewis 1974) and the North Farallon Islands surveyed in April 1 972. By subtracting 1 0,250 breeding pairs for the South Farallon Islands (Ainley and Lewis 1974), a total of between 2,246 and 3,750 breeding pairs can be calculated for the North Farallon Islands in 1972, depending on whether a k correction factor was applied. No other surveys were conducted at the North Farallon Islands until 1980 (Briggs et al. 1983). Other Central California Breeding Colonies Point Reyes Complex Murres were noted breeding on Point Reyes on 23 June 1897, when three eggs were collected by Italian fishermen for O. Emerson (WFVZ Nos. 112,841, 1 14,859-1 14,860). Emerson noted on the specimen card that the colony was "regularly visited by eggers until prohibited by law." On 20 April 1913, E. B. Coues and C. E. Ingalls collected at least nine eggs (set numbers 5,369-5.377; USNM Nos. 34,233-34,241). On 12 June 1932, four eggs were collected by J.S. Rowley at Point Reyes (WFVZ Nos. 26,1 1 1-26.1 14). However, his set numbers were: 2, 8, 10, 11, suggesting that 1 1 or more eggs were collected. On 29 April 1934, 1,500 murres were noted (L. O. Williams, unpublished field notes) and "many young in downy plumage" were noted by McCabe on 5 August 1934 (Allen 1934). One thousand murres were reported breeding at Point Reyes lighthouse rocks on 6 June 1938 (Anonymous 1938). Murres with eggs were noted on 16 May 1939, and 2,200 murres (small downy young present) were counted on 23 June 1939 on the murre rock at the Point Reyes lighthouse (L. O. Williams, unpublished field notes). Williams (1942) noted that murre numbers had "kept up" at Point Reyes during the years from 1933 to 1940. Grinnell and Miller (1944) indicated that breeding had been reported by J. and J. W. Mailliard but did not present other data. One thousand murres were reported by Rigby on 13 July 1947 (L. O. Williams, unpublished field notes). Storer (1952) noted 5,000 murtes and H. Cogswell (unpublished field notes) noted 3,000 murres on the rock below the lighthouse at Point Reyes on 13 February 1 949. It is not clear if Storer counted murres at other locations (in addition to the rock below the lighthouse) from other vantage points along the headlands. However, many murres both below the BIOLOGY AND CONSERVATION OF THE COMMON MURRE 99 lighthouse and at other points along the headlands cannot be viewed from the mainland (M. W. Parker, unpublished data). Thousands were noted on the rocks at Point Reyes on 1 1 June 1950 (Scott 1950). H. Cogswell (unpublished field notes) noted hundreds on the rocks on 1 3 November 1 954. Tuck ( 1 % 1 ) reported 3.000 birds at Point Reyes. Murres arrived on their breeding rocks at Point Reyes on 3 March 1965 (Chase and Paxton 1965). On 27 April 1967. 1,200-1.500 murres were noted breeding at the Point Reyes lighthouse (Chandik and Paxton 1%7; C. J. Ralph. American Birxls Files). Osborne ( 1%9) reported 250 breeding pairs at the rocks north of the Point Reyes lighthouse in July-August 1969. On 22 August 1 970, Osbome and Reynolds ( 1 97 1 ) and Osborne (1972) noted 250 breeding pairs at the rocks north of the Point Reyes lighthouse. On 3 July 1972. Ainley and Whitt (1974) reported 7,640 breeding birds at Point Reyes (based on a ground count adjusted with a k correction factor) that covered all parts of the Point Reyes headlands. On 27 February 1971. several thousand murres were on the rocks under the lighthouse (Mann 1971). Thousands of murres are evident in an aerial photograph (#194) of the Lighthouse Rock area at Point Reyes taken on 15 June 1972 (R. Jurek, unpublished data). On 30 October 1 972, murres were noted on the rocks under the lighthouse (Anonymous 1972). H. Cogswell (unpublished field notes) observed 3,000 murres on the rocks on the north side of the Point Reyes lighthouse on 22 April and 6 May 1978. Points Resistance-Double Confiplex (Point Resistance, Double Point Rocks, and Millers Point Rocks) Griffies ( 1 894) noted that a "broken reef of sharp, low rocks . . . extends at intervals from the north end of Bolinas Bay clear to Point Reyes . . . The patches of white on the larger of these rocks show them to be inhabited [by murres and other seabirds]." Murre breeding was first documented at Point Resistance on 30 May 1926 (Kibbe 1926). Whereas Bolander and Bryant (1935) did not note breeding there in 1929, breeding was again noted at "Bird Rock" by Mrs. Kibbe on 7 June 1931 (Allen 1931 ). Stephens and Pringle (1933) noted that "about a dozen [were] found on Bird Rock in Drake's Bay. June 2. 1931. by Herman de Fremery." Grinnell and Miller (1944) reported breeding at a sea-cliff and islet near the mouth of Bear Valley (i.e.. Point Resistance) in 1935-36. One of two eggs found among Brandt's cormorants (Phalacrocorax penicillatus) nesting on a mainland cliff adjacent to the main breeding rock was collected by A. H. Miller on 1 5 June 1935 (BMVZ No. 3,797). The egg was described as "on decomposed rock and dirt on projecting ridge, moderately steep slope" (A. H. Miller, unpublished field notes). On 7 and 22 April 1962, H. Cogswell (unpublished field notes) noted hundreds on "a rocky islet just off-shore . . . near the end of Bear Valley Road" (i.e.. Point Resistance). Osbome ( 1 969) reported 200 breeding pairs at Point Resistance (referred to as "Rock south Bear Valley") in July-August 1969. In fact. Point Resistance is north of the mouth of Bear Valley and this observation possibly referred to nearby Millers Point Rocks. Osbome and Reynolds (1971) and Osborne (1972) noted 200 breeding pairs in 1970, based on a ground count. Hundreds to thousands of murres are evident in an aerial photograph (#1 86) at Point Resistance taken on 15 June 1972 (R. Jurek. unpublished data). Tuck (1961) reported a colony at Double Point without details. Osbome (1969) reported 700 breeding pairs at Double Point Rocks (referred to as "Rocks north Double Point") in July-August 1969. In fact. Double Point Rocks occur directly off the north point of Double Point and this observation possibly referred to Point Resistance or Millers Point Rocks (see below). Osbome and Reynolds (1971) and Osbome (1972) noted 700 breeding pairs (or 1 .400 murres) from a mainland count at Double Point Rocks in 1970. On 15 April 1971. Ainley and Whitt ( 1974) reported 1 .400 breeding birds at Double Point Rocks (based on a ground count adjusted with a k correction factor ). Thousands of murres are evident in six aerial photographs (#3-5, #183-185) of Double Point Rocks taken on 1 5 June 1972 (R. Jurek, unpublished data). In 1978, S. Allen reported about 3,000 birds (Chan 1981). Varoujean (1979) assigned a 1970 colony of 200 breeding pairs of murres (that had been referred to as "Rock So. Bear Valley" in Osbome and Reynolds 1 97 1 ) to Millers Point Rocks. Sowls et al. (1980) reassigned this observation to Point Resistance — where they had found a substantial colony in 1979 — instead of Millers Point Rocks — where they did not report breeding in 1979-80. However. Briggs et al. (1983) did report breeding murres at Millers Point Rocks in 1 980-82. as did Carter et al. (1992) in 1989. Based on these subsequent observations, it is not clear which of these colonies was being referred to although it was most likely Point Resistance because Millers Point Rocks are smaller rocks and have had only small numbers breeding in most recent years. USGS/BRD/ITR-2000-0012 Devil's Slide Complex (San Pedro Hock and Devil's Slide Rock and Mainland) Bryant ( 1 872) displayed an engraving of San Pedro Rock with birds (probably murres but not identifiable to species) on this rock. He further remarked (p. 567) that "The old promontory, now become an isolated crag, is covered with sea-birds, and its top is already white with their guano, ..." The murre colony at San Pedro Rock was first mentioned by Ray (1904). In 1908, the colony was best documented when it was being extirpated by eggers who still sold murre eggs in the San Francisco market (Ray 1909). On 12 July, about 20 birds and eggshell fragments were left on the rock. However, a fisherman reported collecting "as many as thirty dozen [or 360 single] murre eggs on a trip" in previous years (Ray 1 909). The colony has not been reported as active since, though H. Cogswell (unpublished field notes) noted 40 or more murres on 29 April 1972 as he passed by in a small plane. The Devil's Slide Rock and Mainland colony is located about 1 .6 km ( 1 mile) south of San Pedro Rock, along an inaccessible part of the coast. This colony was not discovered until after Highway 1 was built across Devil's Slide in 1937. Totals of 150-200, 75, and about 100 murres were reported breeding on 5, 8, and 1 1 June 1938, respectively, by Stephens and the Parmenters (Anonymous 1938; Linsdale 1938). On 27 July 1939, Parmenter reported murres "still nesting" at Devil's Slide Rock (Anonymous 1939; Sibley 1952). Similarly, Parmenter noted 100 murres on Devil's Slide Rock on 9, 24 and 28 July 1941 (L. O. Williams, unpublished field notes). On 11 April 1954, 13 July 1954, and 12 July 1959, H. Cogswell (unpublished field notes) noted 200, 180, and 200 murres on Devil's Slide Rock, respectively. In 1970, Osborne and Reynolds (1971) and Osborne ( 1 972) reported 350 breeding pairs from a mainland count. Hundreds to thousands of murres are evident in a photograph (without additional informafion) that was probably taken in 1970-72, possibly by R. Jurek or J. G. Reynolds (Sowls et al. 1980; unpublished data). These colonies are located close to the Golden Gate, so murres there probably were affected heavily by oil pollution in the early twentieth century (Ainley and Lewis 1974; Chapter 3), which may have contributed, with egging, to the loss of the San Pedro Rock colony at this time. Both colonies also probably were affected by the construction (1905-08) and operation (1908-20) of the Ocean Shore Railroad that ran from San Francisco to Santa Cruz. In 1906, a tunnel was blasted through San Pedro Point, a railroad bed was blasted along Devil's Slide, and a large "saddle cut" was blasted south of Devil's Slide (Stanger 1963; VanderWerf 1992). Railroad construction between San Francisco and Granada was completed in 1908. In 1908, a fisherman reported that "the birds had become scarce [at San Pedro Rock] owing to the continued blasting" during railroad construction (Ray 1909). The railroad was plagued by landslides and was often rebuilt along Devil's Slide until its demise in 1920. The railroad was built by Greek, Sikh, and Japanese immigrant workers who lived in the general area. Greek immigrants were well known for egging activities at the South Farallon Islands between 1880 and 1900 (see above). The railroad also brought many people to the San Pedro Point area. In the spring of 1 908, 3,000 excursionists traveled from San Francisco to Tobin Station near San Pedro Point, prior to the opening of the railroad to Half Moon Bay (VanderWerf 1992). Thus, the railroad may have provided many opportunities for people to discover breeding murres and conduct egging at San Pedro Rock. Castle-Hurricane Complex (Hurricane Point Rocks and Castle Rocks and Mainland) Murres were first noted breeding at Hurricane Point Rocks in 1940, after Highway 1 was opened through this previously inaccessible (except by boat) area in 1938. Murres apparently bred only at Hurricane Point Rocks, especially the larger rock, between 1940 and 1950. On 23 May, about 200 murres were noted on Hurricane Point Rocks and they were present on 25 May 1940. Williams remarked that "Guy Emerson discovered colony on May 21 or 22 1940" (L. O. Williams, unpublished field notes). From 1940 to 1945, L. O. Williams (unpublished field notes) recorded murres several times at Hurricane Point Rocks but not at the nearby Castle Rocks and Mainland colony, where he did record other bird species. Murre observations were reported as follows: between 270 and 300 on 19 June 1940, 200 on 15 July 1940, 300 on 1 1 July 1941, 280 on 25 April 1942, 500 on 29 June 1943, 500 on 29 June 1943, with the remark that the colony had "seemed to show a slight increase over 1940", and 600 on 20 May 1945. Several hundreds also were reported by the Andersons at Hurricane Point Rocks on 23 June 1950 (L. O. Williams, unpublished field notes). On 12 June 1955, Williams reported 530 birds "present in colony" at Hurricane Point Rocks (American Birds Files; Cogswell and Pray 1955b). Storer (1952) reported Hurricane Point as a colony, but without details. Osborne and Reynolds ( 1 97 1 ) and Osborne ( 1 972) reported 200 and 100 breeding pairs at Hurricane Point Rocks and Castle Rocks and Mainland, respectively. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 101 on 6 May 1970. However, these estimates were based on counts of 400 and 300 birds, respectively (Osborne and Reynolds 1971; Varoujean 1979). Human impacts to these murre colonies may date back to the early nineteenth century when Russian hunters worked along coastal areas (Essig et al. 1 99 1 ). In the 1 850s, a Chinese abalone fishery operated out of Point Lobos and fishermen worked the rocks at least as far south as Point Sur (Armentrout-Ma 1981; Lydon 1985). On 20 April 1875, the steamship Ventura ran aground on either Castle Rocks and Mainland or Hurricane Point Rocks (Reinstedt 1975). Several shipwrecks have occurred in the vicinity of Point Sur. Possible Historical Colonies in Marin and San Francisco Counties Murres may have previously bred at other locations with suitable habitat between the Russian River and San Pedro Rock which probably would have been extirpated by the activities of early settlers, including egging, before documentation as murre colonies. Bryant (1848) noted that, in 1847, "some of the islands in the harbor, near San Francisco, are white with guano deposited by these birds [i.e., "waterbirds"] . and boat loads of eggs were taken from them." White (1995) considered this observation to probably refer to murre egging at the Farallon Islands but several potential breeding islands for murres and other seabirds exist at the entrance and inside the mouth of San Francisco Bay. Bryant (1872) displayed several engravings which showed birds (possibly murres but not identifiable to species) on various rocks in this area. Near the town of "Two Rocks" (i.e.. between Estero Americano and Estero San Antonio in northern Marin County), Bryant remarked (p. 560) that "The innumerable birds that make their nests upon the broad, flat summits of these rocks are not so kindly treated, being robbed at regular internals by an egg company formed for that purpose. Wild and precipitous as these rocks appear, they can be scaled without difficulty, and the time will inevitably come when the birds will learn to avoid the place, and these rocks will lose their chief attraction - their chief attraction, it must be understood, for the multitude." Aldrich (1939) noted murres "congregated" on Seal Rocks, along with sea lions and other seabird species. Howexer, no details were provided and other observers of this frequently-visited area did not note breeding there. Possible Historical Colonies in Monterey and San Luis Obispo Counties There is no specific documentation of murres breeding between Hurricane Point Rocks in central Monterey County and Prince Island in the northern Channel Islands of southern California. Dawson (1923) indicated that breeding occurred at the Farallon Islands and "in lesser numbers south to Prince Islet . . ." but with no other details. Several other authors also have reported breeding as far south as Prince Island without details. Murres may have previously bred at several undocumented locations with suitable habitat before extirpation by human activities or natural factors. European settlement of parts of this coast occurred in the late eighteenth and early nineteenth centuries when large and small ranches, towns, and ports were established. Early settlers likely harvested birds, eggs, and guano from small islands, close to shore and accessible to small boats. For example, Piedras Blancas Island was an early and major landmark for coastal shipping for the Spanish galleons returning from the Philippines in the eighteenth cenmry and was located beside a large ranch and port set up for sending food and other products to inland missions at San Antonio de Padua (est 1 77 1 ) and San Miguel Arcangel (est. 1 797) (Bancroft 1886; Hamilton 1974). Native people were sent to the coast daily to obtain sea food that probably included seabird meat and eggs for the missions. For three years in the 1 880s, guano was harvested from this rock and sent to San Francisco (Hamilton 1974). Murres breeding at Piedras Blancas Island probably would have been extirpated because of eariy human activities. Many other human activities also occurred along this coast (including hunting, mining, logging, shipping, fishing, etc.), especially since 1850 when human populations expanded rapidly (Hamilton 1974). Russian hunters also worked this area in the nineteenth century and may have egged and eliminated small colonies even earlier (Essig etal. 1991). Southern California Colonies Prince Complex Hunt et al. (1979) summarized data originally provided by L. Kiff (personal communication) for the southernmost known colony of the common murre at Prince Island, just north of San Miguel Island off southern California. The colony disappeared in the early twentieth century, possibly due in part to specimen collecting for private egg collections. I reviewed egg records and other information to further investigate the loss of this colony. Several details on the egg specimens that I examined differed from those presented in Hunt et al. (1979), possibly because of more recent accessions to the WFVZ collection as well as different data treatment. Between 60 and 227 murre eggs were collected at Prince Island between 1 885 and 1912. Most 102 USGS/BRD/ITR-2000-0012 were collected between 1 905 and 1910 when only about 100 pairs bred at the colony. On 18 June 1 885, W. C. Bradbury collected at least one egg (set number 2) at Prince Island (WFVZ No. 4,385). On 24 June 1885, Bradbury collected at least one more egg (set number 1 ; WFVZ No. 4,377). In late July 1886, Streator (1888) did not mention murres at Prince Island but birds might have finished breeding. On 18 July 1894, Bradbury returned and collected at least two more eggs (WFVZ Nos. 4,38 1 and 4,384); one egg was reported from the "Isle of Santa Barbara" but another was reported from Prince Island on the same day. Breeding murres have never been reported from Santa Barbara Island proper. On 10 July 1 895, Bradbury collected at least one egg (set number 1 ; WFVZ No. 4,382). In June 1 896. Bradbury obtained another egg (set number 1; WFVZ No. 4,380). Hunt et al. (1979) reported eight eggs taken by Bradbury on 24 June 1885, based on specimen numbers (WFVZ Nos. 4,377^,386) but examination of the egg specimen cards indicates that they were collected in different years and dates as shown above. I could not locate WFVZ No. 4,386, reported by Hunt et al. (1979). Eleven eggs (incubation well advanced in each egg) were collected by H. S. Burt from a ledge on a cliff running back in large cave about 6-9 m (20-30 feet) above the water. Burt estimated about 100 birds breeding on 5 June 1905 (WFVZ Nos. 80,934-80,944; set numbers 4-13, 18). Probably 1 8 eggs were collected although Hunt et al. (1979) reported only 13. On 2 June 1906, H. Hedrick collected at least one egg (set number 33) from Prince Island (WFVZ No. 46,466). On 4 June 1906, Hedrick returned and collected another egg (set number 8) from a damp cave (WFVZ No. 140,459). On 6 June 1906, J. S. Appleton collected at least five fresh eggs (WFVZ Nos. 76,219-76,222; 76,224; set numbers 34, 38, 52, 54, 56) and estimated 100 pairs breeding on Prince Island. He noted that eggs were laid on bare rocks and many eggs had been broken by waves. At least 10 and as many as 56 or more eggs probably were collected by Appleton on this visit. On 10 June 1906, Hedrick returned and obtained at least one egg (WFVZ No. 46,470; set number 30). He listed nearby San Miguel Island as the collection locality but this was probably Prince Island. Perhaps 30 or more eggs were collected by Hedrick on this visit. Two or three colonies of 5-50 murres each were reported breeding on the island by Appleton (Hunt et al. 1979). In 1906, 1 determined that between 8 and 127 eggs were collected, based on the information above. Hunt et al. (1979) reported 20-50 eggs were collected in 1906 by Hedrick and Appleton. Several egg collectors collected murre eggs (that were mostly advanced in incubation), caught adult birds that did not leave their breeding sites, and estimated about 100 breeding pairs on Prince Island on 15 June 1910 (Willet 1910; Hunt et al. 1979). Eight eggs collected by G. Willet were found on the floor of a cave in rocks (WFVZ nos. 6,174; 45,894-45,895; 80,929- 80,933; set numbers 348, 349, 35 1 , 354-356, 359, 360). Probably at least 13 eggs were collected by Willet. Four eggs collected by J. S. Appleton were obtained from the same cave ledge (WFVZ Nos. 32, 1 1 3-32, 1 1 4; 76,2 1 7- 76,218; set numbers 31, 35, 36, 37). He probably collected at least seven and perhaps 37 or more eggs. Twelve eggs collected by A. Jay also were obtained from the same cave ledge (WFVZ Nos. 109,801-109,8 12, set numbers 1-12). Eight eggs collected by O. W. Howard apparently were obtained from the same cave ledge (WFVZ Nos. 46,410-46,417; set numbers 1-3 and 5-9). At least nine eggs probably were collected. Together, I determined that between 32 and 71 eggs were collected by these collectors from one small cave ledge on that one day. Hunt et al. (1979) reported at least 29 eggs were collected on this trip. They also noted certain specimen numbers that I could not find (WFVZ Nos. 6,172-6,173; DM [unknown collection] Nos. 1,226; 1,231). The last egg record available for Prince Island was obtained on 12 July 1912. G. K. Synder collected at least three addled eggs on rocky ledges high above the water (WFVZ Nos. 47,518^7,520). He indicated that at least four sets of eggs were collected. Wright and Synder (1913) reported several small colonies on the "high overhanging ledges" and many chicks on 12 July 1912. After 1912, the only record of murres on Prince Island was one bird seen on 18 April 1939 (Sumner 1939, Hunt et al. 1979). It is unlikely that any murres escaped detection of egg collectors. D. Bleitz (unpublished field notes) noted that no murres were breeding on 25 July 1961. Two birds in breeding (alternate) plumage were observed on Prince Island on 23 July 1976(McCaskie 1976; Garrett and Dunn 1981), indicating that nonbreeding attendance may occur sporadically. Detailed surveys in 1975-77 (Hunt et al. 1979) and 1991, 1994, and 1995 (Carter et al. 1992; McChesney et al. 1995; H. R. Carter, unpublished data) failed to find any murres on land at Prince Island and virtually none at sea nearby during the breeding season. In 1999, murres were noted on land at Prince Island during the early breeding season (see Chapter 2 text). In summary, the extensive egging evident in these records as well as the close temporal proximity of the collecting and extirpation support the assertion by Hunt et al. (1979) that specimen collecting contributed to BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 03 and may have been the main factor leading to final extirpation of this colony. The colony also may have been affected in the nineteenth and early twentieth centuries by undocumented human disturbance, egging, hunting, deaths from oiling, climate change, or factors at the southern edge of the breeding range (Hunt et al. 1 980). Other murre colonies also could have existed in the northern Channel Islands (especially at nearby Castle Rock off San Miguel Island where suitable habitat exists) but were extirpated before the 1 880s when egg collecting became focused at Prince Island. Northern California Colonies Castle Bock (Castle Complex) Castle Rock probably was egged heavily by early residents of Crescent City (e.g., about 800 residents by 1854 [Smith 1989]) because of easy access by small boat. The first record of murre breeding on Castle Rock was an egg collected on 6 July 1894, without other data, in the egg collection of C. I. Clay which is housed at the museum within the Department of Wildlife at Humboldt State University (HSUWM No. 605). Numerous eggs were collected from Castle Rock between 1917 and 1 935, after the South Farallon Islands and Prince Island no longer provided specimens for collectors (see above). On 20-22 July 1917, C. I. Clay collected at least 4 eggs and murres were noted only as "seen" (HSUWM Nos. 345-347, 1387; C. I. Clay, unpublished field notes in the HSU Special Collections Library [HSU-SCL]; see Osborne 1972). On 23 June 1923. at least two eggs were collected, without other data (HSUWM Nos. 1615, 1618). On 18 May 1925, at least one egg was collected (HSUWM No. 1088). On 2 June 1 924. F. J. Smith (probably with C. I. Clay) collected at least five eggs; two eggs were marked as sets numbers 3 and 10 (WFVZ Nos. 32,111; 32,115) from a "small nesting colony." whereas three other eggs had the same date, without other data (HSUWM Nos. 309, 1614, 1616). On 23-25 June 1925, F. J. Smith and C. I. Clay collected at least seven eggs and one small chick that was found dead (MCZ 328596). Two eggs were marked as set numbers 2 and 40 (WFVZ Nos. 73.885; 140.513) and three eggs were marked as set numbers 1, 2, and 3 (MCZ 942 1 -9423 ). whereas two other eggs had the same dates without other data (HSUWM Nos. 1386, 1613). One other egg bore only the date 1925 (HSUWM No. 1623). Clay (unpublished notes in the HSUWM egg collection) made a list of eggs of several seabirds collected at Castle Rock on 24 July 1925, noting 50 murre eggs collected. In June 1926. at least one egg was collected (HSUWM No. 1621). whereas one other egg bore only the date 1926 (HSUWM No. 1617). On 22- 24 June 1928. F J. Smith and C. I. Clay collected at least 10 eggs (WFVZ No. 73,886; BMVZ Nos. 13,284- 13,291; HSUWM No. 296). Clay (unpublished notes in the HSUWM egg collection) made a list of eggs of several seabirds collected at Castle Rock on 24 June 1928, noting 100 murre eggs collected. On 17-18 May 1929, F. J. Smith (probably with C. I. Clay) collected at least 1 5 eggs: three eggs were marked with set numbers 9, 10, and 16 (WFVZ Nos. 37,036; 73,887; 73,888), whereas 1 2 eggs had no other data (HSUWM Nos. 293, 294, 302, 310, 340-344, 684 [note: HSUWM Nos. 340, 342, and 344 include two eggs per specimen number]). On 25 May 1929, J. T. Fraser collected at least one egg, marked as set number 3/29 (WFVZ No. 88.133). On 9 July 1929, G. D. Atwell collected at least three eggs, marked as set numbers 117-1 19 (HSUWM Nos. 1738- 1740). On 18 May 1930, L. Zerlang and J. T. Fraser collected at least four eggs: three eggs were marked with Zerlang's set numbers 1 , 2, and E5, and one egg was marked with Fraser's set number 2 (WFVZ Nos. 37,036; 73,887; 73,888). On 28 June 1930, at least six eggs were collected, probably by C. I. Clay (HSUWM Nos. 295, 299. 669, 67 1 , 675, 676). On 20 May 1 93 1 . L. Zerlang collected at least one egg, marked as set number 4 (WFVZ No. 47,408). On 27 June 1931. at least four eggs were collected, probably by C. I. Clay (HSUWM Nos. 297, 298. 300. 301). On 12 June 1932, L. Zerlang and J. T. Fraser collected at least four eggs: two were marked with Zerlang's set numbers 17 and 57, and two with Fraser's set numbers 332 and 532 (WFVZ Nos. 46,406; 47,409; 88,111: and 88,113). On 20 May 1934, C. I. Clay collected at least ten eggs, of which nine eggs are in the HSUWM collection (HSUWM Nos. 1,089; 1,090; 1,095; 1,096: 1,098; 1,100; 1,105; 1,107; and 1,680). Clay (HSU-SCL unpublished field notes) provided additional information for each egg collected (field nos. 2305- 2310, 2313-2317), including the following notes of interest: No. 2305 (HSUWM No. 1,100) - "Colony murres on north side and about 100 feet above sea level; large colony with eggs close together"; No. 2,306 (HSUWM No. 1095) - "All the eggs in 3 major colonies were laid on bare rock; in some cases extremely rough"; No. 2,310 (HSUWM No. 1090) - "... taken on extreme top of the highest peak on rock. Estimated 167' above sea level"; No. 2,313 (HSUWM No. 1089) - "... in large colony on extreme seaward side of island"; No. 2,315 (HSUWM No. 1,089) - "This egg placed in center of large colony of murres on the east side of the island. Birds in this colony touched each other, while on the nest, they were so thick. This colony laid eggs right out to the edge of a more than 100 foot cliff..."; and No. 2,3 1 6 - "Same nesting side as the last runt egg [i .e.. No. 2,315]... The colony was the most compact nesting of 104 USGS/BRD/ITR-2000-0012 any of the murre colonies... ." In addition, Clay (HSU- SCL unpublished field notes) made the following general notes: "The California Murre were in full nesting. Eggs fresh to slight incubation"; and "The greedy Western Gull was seen to make off with a murre's egg at every opportunity, holding it firmly between his beaks, with the large end towards his mouth." In June 1934, Fraser (Osborne 1972) also noted breeding murres at Castle Rock. On 18-20 May 1935, C. I. Clay collected at least 1 3 eggs, of which 1 2 are specimens in the HSUWM collection (HSUWM Nos. 1,091-1,094; 1,097; 1,099; 1,101-1,103; 1,106; 1,108; and 1,109). Clay (HSU-SCL unpublished field notes) noted each of the 13 eggs collected (field nos. 2,337-2,350) on the "north high point of island" with the following notes of interest: "Three separate rookeries are on the island.. ..The murres were all sitting on their eggs"; and field no. 2,338 (HSUWM No. 1,094) - "This was 11 P.M. Bright moonlight overhead. The colony next our position crowded close against each other as we approached their position." Talmadge also noted breeding murres in two large colonies in the mid- 1930s (Osborne 1972). In addition to the above egg specimens, another 24 eggs without any data are housed in the HSUWM collection that were probably collected by C. I. Clay at Castle Rock between 1917 and 1935. On 27 May 1956, L. T. Stevens noted "10,000 pair nesting" and collected at least 1 8 eggs with set numbers ranging between 2402 and 2504. Ten eggs are in the WFVZ collection (WFVZ Nos. 34,224; 78,967-78,969; 124,155-124,157; 132,452; 145,266; and 145,267), six eggs are in the SBNHM collection (SBNHM Nos. 2,403; 2,412-2,413; and three without catalogue numbers), and two eggs are in the USNM collection (USNM Nos. 46,569; 46,574). On 28 May 1961, L. T. Stevens and J. D. Daynes noted 5,000 breeding pairs or 5,000 birds at Castle Rock and collected at least 28 eggs with Stevens' set numbers ranging between 3172 and 3209 and Dayne's set numbers ranging between 9 and 27. Twenty- four eggs are in the WFVZ collection (WFVZ Nos. 30,161-30,162; 34,205-34,215; 34,217-34,222; 34,225-34,228; 145,268) and four eggs are in the USNM collection (USNM Nos. 46,570-46,573). In July- August 1969, breeding pairs were estimated at 5,400 (Osborne 1969) although surveys were conducted late in the season. On 7 February 1970, 250 birds were present with irregular attendance until breeding started. In 1970, about 20,000 pairs were reported breeding, although between 16,600 and 32,000 birds were counted on various dates in April-June (Osborne 1971). Osborne (1972) reported 40,000 breeding pairs in June 1970 and noted that the murre population of northern California had increased since 1900 when egg predation by native people and European immigrants began to decline. If a ^ correction factor was applied to 1970 counts, a range of 27,700- 53,400 breeding birds or 14,000-27,000 pairs can be calculated. Because low counts may have occurred prior to egg laying, rough counting techniques were used, and aerial photograph counts are often greater than visual estimates, the upper end of this range is compared to 1979 (see Chapter 2 text). On 18 July 1976, 1,000 were reported (T. Schulenberg, American Birds Files and personal communication). H. Cogswell (unpublished field notes) roughly estimated at least 50,000 from a small aircraft on 2 July 1977, as well as 300,000 murres from a telescope count from the adjacent mainland, hundreds of meters away. Whaler Island (Castle Complex) On 23 June 1928, F. J. Smith collected one murre egg (set number 8) on "Whale [sic] Island, Crescent City, California . . . about 80 feet [24 m] above the sea" (BMVZ No. 13,292). He also collected eggs from nearby Castle Rock at this time (see earlier). Whaler Island was a well-known location at Crescent City harbor, so there does not seem to have been confusion between Whaler Island and Castle Rock. This is the only available documentation of murres breeding at Whaler Island. Murres were not reported there by egg collectors and early naturalists in May 1916, July 1919, 22 March 1925, 20 May 1934, or June 1939 when thousands of nesting Leach's and fork-tailed storm-petrels (Oceanodroma leucorhoa and O. furcata) and other species were noted (Howell 1920; Osborne 1972; Clay, HSU-SCL unpublished field notes). A small breakwater was completed by 1939 connecting the island to the mainland. In the early 1950s, the island was partly quarried and the breakwater strengthened. In 1969, Osborne (1972) visited the island and noted rats (Rattus sp.) and no breeding seabirds. False Klamath Complex Dawson (1923) noted breeding by murres on rocks of Humboldt and Del Norte Counties but provided no exact breeding localities. A large congregation of murres was noted by Kelly on the large rock offshore near Requa (probably False Klamath Rock) on 1-6 June 1941 and the "whole side of rock was covered with birds" (L. O. Williams, unpublished field notes). Clay (HSU-SCL unpublished field notes) did not provide any earlier observations of seabirds at False Klamath Rock. In 1969, 5,000 breeding pairs were reported (Osborne 1971; Osborne and Reynolds 1 97 1 ), apparently from an aerial BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 05 count (Osborne 1972). However. 2.500 breeding pairs were reported in 1969 by Osborne (1969). Osborne (1972) reported 10.000 breeding pairs in 1970. On 18 July 1976. 1 .200 murres were reported at False Klamath Rock (T. Schulenberg. American Birds Files and personal communication). Redding Complex Osbonie (1972) reported that Clay told him that murres bred on Redding Rock in the 1930s. No reference to this obser\'ation or any visit to Redding Rock was reported on paper by Clay (HSU-SCL unpublished field notes). Osborne (1971) and Osborne and Reynolds (1971) noted 200 breeding pairs at Redding Rock in 1%9. Osborne ( 1972) noted 300 breeding pairs in 1970 based on an aerial survey on 12 May. A navigational aid light was placed on Redding Rock prior to the 1950s. Annual maintenance activities by the U.S. Coast Guard have affected the colony (see Chapter 2 text). Trinidad Complex (Green Hock, Flatiron Rock, Pilot Rock, Blank Rock, White Rock, and Sea Lion Rock) Trinidad Bay was discovered on 9 June 1775 by Juan Francisco de la Bodega y Cuadra aboard the Spanish ship Sonora (Coy 1929). The pilot A. Mourelle noted: "At the entrance of the port is a small island of considerable height, without a single plant upon it [Pilot Rock]; and on the sides of the coast are high rocks, which are very convenient for disembarking [e.g., Flatiron Rock]; ...'" Thus, some harvesting of seabirds or their eggs may have occurred. In late June and early July 1817. the British ship Columbia visited and the chief officer noted: "This bay is fidl of high rocks, which are always co\ ered with birds, and round it are scattered many Indian villages." Trinidad was one of the first settlements along the northern California coast, estabUshed in 1 850. These rocks probably were egged heavily by early residents but egging by native people also probably took place because of the accessibility of these colonies by canoe from the Yurok village of Tsurai (Heizer and Mills 1991). On 2 July 1897. mane eggs were collected from unidentified "rocks off the coast of Humboldt Co." (probably off Trinidad) for A. M. Shields. A total of 72 eggs were found in the WFVZ collection (set numbers between 3 and 198). On 18 July 1900. murre eggs were collected from unidentified "rocky islands of the coast of Humboldt Co for L. Kessing." A total of 343 eggs were found in the WFVZ collection (sets of 20 eggs each, set numbers between 1 and 133); thus, as many as 2.660 eggs may have been collected. On 28 June 1 901 . at least four murre eggs were collected from unidentified "islands off Humboldt Coimty . . . collected by a sailor for W. L. Chambers" (WFVZ 47.401-47.402; 47.664; 80.928). This group of colonies near Trinidad in Humboldt County probably were the breeding rocks in Humboldt County referred to by Dawson (1923). (jieen Rock was first reported as a breeding colony in 1930s by Talmadge (Osborne 1972). On 1 1 August 1938, Clay (HSU-SCL unpublished field notes) reported finding a dead murre "in the surf at mouth of Luffenholtz Creek, 2 miles south of Trinidad ... California Murre nest on fishermen's rock [i.e.. Green Rock] 1 '/z miles north of Trinidad." On 10 May 1941. Clay (HSU-SCL unpublished field notes) noted a substantial colony at "Fishermen's Rock" (i.e.. Green Rock) and described it as follows: "A considerable colony of California Murres nest on this bold, rather round dome 125 feet above the waterline. I have worked other rocks along this locality many times in past years; but never this particular one; it being the only accessible one with a murre rookery in these parts... I doubled back and up an sought ridge of easy going soon to hear the incessant grumbling roar of the approximately 2000 California Murres which were packed tight on the very top of the rocky dome. I was on a rather, grassy flat 10 feet wide running in a circle at the bonom of a 6 foot wall, just out of sight of the murre colony." These notes and the lack of observations at other nearby islands suggest that murres only bred on Gieen Rock in the Trinidad area from at least 1910 to the early 1940s. W. Anderson (HSU-SCL unpublished field notes) reported murres as "numerous on sea cliffs. Trinidad" on 15-16 May 1943 and "A few left on rocks off Trinidad" on 15 August 1943. These obser\'ations appear to refer to Green Rock alone, but also may refer to Flatiron Rock (see below). Murres were not reported on the cliffs of Trinidad Head in 1910-40 by Clay (HSU- SCL unpublished field notes) who conducted extensive collections in this area. Anderson (HSU-SCL unpublished field notes) also noted murres breeding, probably at Green Rock and Flatiron Rock, in 1947 (see below). On 10 June 1948. two eggs (set number 236) were collected from a "large colony on island near Trinidad" (probably Green Rock but possibly Flatiron Rock; see below) by A. Andresen (WFVZ No. 68,333). Osborne (1%9) reported 1,200 breeding pairs in July- August 1969. Osborne (1971) and Osborne and Reynolds ( 1 97 1 ) noted 1 0.000 breeding pairs of murres in 1970. In fact, counts ranged between 6.0(X) and 20.000 birds on various dates in April-June 1970 and colony attendance began in February 1970. Osborne (1972) reported 20.000-24.000 breeding pairs in 1969-70. If a it correction factor was applied to 1 970 counts, a range of 10,000-33.000 breeding birds or 5,000-17,000 pairs 106 USGS/BRD/ITR-2000-0012 can be calculated. Since low counts may have occurred prior to egg laying, rough counting techniques were used, and visual counts were made, the actual number was probably between 10,000 and 15,000 pairs. Clay (HSU-SCL unpublished field notes) did not note murres on several egg collecting trips to "Off Trinidad Rock" (i.e., Flatiron Rock) on 22 May 1910, 1 6 July 1 9 1 1 , and 2 1 July 1912. Osborne ( 1 972) reported Clay's lack of murre observations in these years and in 1934. Greater accessibility of this rock by canoe (native people) or boat (eggers) may have resulted in earlier colony extirpation. However, on 31 May 1947, W. Anderson (HSU-SCL unpublished field notes) noted that murres were "apparently nesting in considerable numbers on two islands in Trinidad region." On 1 3 July 1947, Anderson (HSU-SCL unpublished field notes) further noted: "Great numbers of half-grown downy young seen from skiff on the larger of the 2 Murre rocks. Adults bringing single fish on each trip." Murres likely expanded from Green Rock onto Flatiron Rock, which has extensive breeding habitat and is located near Green Rock. Osborne (1969) reported 1,000 breeding pairs in July-August 1969. Osborne (1971, 1972) and Osborne and Reynolds (1971) noted 2,500 breeding pairs in 1970, based on the highest mainland count of 5,000 birds on 5 April 1970. In fact, counts ranged from 1 , 100 to 5,000 in April-June 1970 and murres began attendance of the colony in early February 1970 (Osborne 1 97 1 ). Osborne ( 1 97 1 ) also noted an estimate of 2,000 breeding pairs that seems to be an error. Osborne (1972) reported 5,200. Varoujean (1979) and Sowls et al. (1980) cited this value as 5,000 breeding pairs in 1969-70. If a ^ correction factor was applied to 1970 counts, 2,000-8,000 breeding birds or 1,000-4,000 pairs can be calculated. Because low counts may have occurred prior to egg laying, rough counting techniques were used, and aerial photograph counts are often greater than visual estimates, the upper end of this range is compared to 1979 (see Chapter 2 text). On 6 February 1971, 5,000 birds (95% in breeding plumage) were reported at Flatiron Rock (DeSante and Wang 1971; R. A. Rowlett and R. Le Valley, American Birds Files). Several observations of murres at Green and Ratiron rocks were recorded by R. A. Erickson, T. S. Schulenberg, and others between 1 973 and 1 976 (R. A. Erickson and T. S. Schulenberg, unpublished data; American Birds Files), including many hundreds on 16 April 1973; 6,000 on 1 7 March 1 974 (Greenburg and Stallcup 1 974); 5,000 on 6 April 1974; 5,500 on 19 April 1974; 4,500 on 4 May 1974; 4,500 on 8 June 1974; 2,000 on 4 May 1975; 12 on 17 August 1975; and 2,500 on 12 June 1976. Osborne (1972) reported murres at Pilot Rock in 1969 although breeding was not noted there by Osborne and Reynolds ( 1 97 1 ). Murres also were noted in 1 966- 69 by S. W. Harris (Osborne 1972). Murres were not reported breeding at Blank Rock in 1969-70 (Osborne 1969, 1971, 1972; Osborne and Reynolds 1 97 1 ). However, 1 ,000 and 5,000 murres were reported at Blank Rock on 13 and 21 March 1965, respectively, by F. Zeillemaker (R. A. Erickson, unpublished data, American Birds Files). Osborne (1971, 1972) and Osborne and Reynolds ( 1 97 1 ) noted 600 breeding pairs at White Rock in 1 969, based on mainland counts. Osborne ( 1 969) reported 250 breeding pairs in July-August 1969. Clay and Hallmark (Osborne 1972) noted that murres bred on Sea Lion Rock before the 1 950s when the entire south half of the rock fell into the water. Previously, murres had bred on the flat top of the rock. Breeding has not been reported since then (Osborne 1972; Sowls et al. 1980; Carter et al. 1992). Cape Mendocino Complex (False Cape Rocks and Steamboat Rock) Osborne ( 1 969) first reported 350 breeding pairs at False Cape Rocks in July-August 1969. In 1969-70, Osborne ( 1 97 1 ) and Osborne and Reynolds ( 1 97 1 ) noted 600 breeding pairs at False Cape Rocks (based on a July 1969 aerial count). Osborne (1972) reported 800 breeding pairs at False Cape Rocks in 1969, based on an aerial count (reported as 1970 in Varoujean 1979 and Sowls et al. 1980). Clay (HSU-SCL unpublished field notes) did not report any earlier visits to False Cape Rocks. On 7 July 1917, Clay (HSU-SCL unpublished field notes) did not note murres at Steamboat Rock but did note that "... a great many Brandt cormorants were seen and they appeared to be nesting in great numbers." It is possible that no murres bred within this complex at this time, given this observation and Clay's comment on 10 May 1941 that murres bred only at Green Rock "in these parts" (see above). However, this observation was made from the adjacent mainland and most of the murre breeding areas on this rock are not visible from shore. Osborne (1969) reported 150 breeding pairs at Steamboat Rock in July-August 1969. Osborne ( 1 972) indicated that 300 birds were observed on 16 July 1969. In 1970, 300 pairs bred, based on ground and aerial counts in 1969-70 (Osborne 1971; 1972; Osborne and Reynolds 1971). BIOLOGY AND CONSERVATION OF THE COMMON MURRE 107 Although Sugarloaf Rock (near False Cape and Steamboat Rocks) has suitable breeding habitat, murres have been noted there only once and have not been recorded breeding there. Briggs et al. (1983) reported 334 birds at the rock in July 1981, but none during other May and July surveys in 1980-82. I did not, therefore, consider these birds to be breeding, but birds at this colony may have abandoned without any documentation of earlier breeding. Mendocino County Colonies Murres had not been reported breeding in Mendocino and Sonoma Counties before 1979 when breeding was first reported at Cape Vizcaino (Sowls et al. 1980). Osborne and Reynolds (1971) did not note any murres there in 1969-70 although other nesting species were recorded at many rocks and islands. Osborne's surveys may have been conducted too late in the season to detect the Cape Vizcaino colony. Murres may have bred at sites throughout Mendocino and Sonoma Counties in the past but been extirpated by early settlers since 1 850 (Lorentzen 1 995 ). This area was colonized rapidly during and after the Gold Rush when many small coastal logging communities sprung up along the coast. Most of the islands along this coast are small, close to shore, and easily accessible by small boat. Accessible colonies probably would have been egged heavily during the early years of colonization by U. S. settlers when food was scarce. In addition, native peoples in canoes also may have adversely affected murre colonies before and during U. S. settlement. There is little documentation of egging in this area. In the first week of June 1900, however, 24 murre eggs obtained by fishermen from somewhere along the "Mendocino coast" were bought in the San Francisco market by L. Kessing for D. A. Cohen. The labels of seven specimens in the WFVZ give this information (WFVZ Nos. 1 17.680-1 17,685). However, murre eggs also were obtained for L. Kessing on unidentified rocks in Humboldt County in July 19(X) (see Trinidad Complex above). Thus, it is possible that an incorrect general location was applied to these 24 eggs. If murres did breed along the Mendocino coast, their colonies probably were adversely affected by the construction of log chutes, piers, and wharves. This area has no large natural harbors and chutes were built for loading logs onto ships from coastal bluffs. Often, the ocean end of a chute or pier was built on small offshore rocks located close to shore at several points along the coast (Sullenberger 1980: Hendrickson 1994). One of the largest wharfs was at Cottaneva (or Rockport) where the first suspension bridge on the West Coast was constructed in 1 877. The bridge extended over 92 m (275 feet) of ocean onto several offshore rocks, the largest of which was called "Sea Lion Rock" (Mendocino Historical Research, Inc. 1978: Lorentzen 1995: Cook and Hawk 1999). These rocks were cut down to form a flat surface for bridge construction and for storing lumber. In 1 888, the wharf was rebuilt and fortified in the same location. The mill closed for 10 years during the Great Depression (about 1928-38), during which time the bridge fell down. The mill reopened in 1938 and a skyline was built between the mainland and the rock. The skyline was used for a short period to load boats before the switch to hauling lumber by truck. The mill burned in 1942 (Lorentzen 1995; Cook and Hawk 1999). Since 1989. these rocks (now called Rockport Rocks) have been used for breeding by murres (Carter et al. 1992), despite the cement supports that are still visible on the rocks. It is likely that murres were forced off these rocks when the wharf was built. Other colonies probably were similarly affected by wharfs and chutes. Murres breeding near Fort Ross or other areas farther north also would have been heavily egged by the resident Russians in the early nineteenth century, based on their activities at the Farallon Islands (see above). Unfortunately, the coasts of Sonoma and Mendocino Counties were visited little by early ornithologists and breeding seabirds were poorly recorded and poorly known. In 1997. murres were confirmed breeding at three other colonies along the Mendocino coast (see Chapter 2 text). BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 09 Appendix C Population data for common murre {Una aalge californica) colonies in California, 1979-1986 (prepared by H. R. Carter and J. E. Takekawa) Table. Summary of whole-colony counts of common mures (Uria aalge californica ) from aerial photographic and other surveys conducted in California in 1 979-1 986 by the U.S. Fish and Wildlife Service, University of California, and other groups. See extended table legend at end of this appendix for format. Colony Colony name Year number ^9^sr> ^9W*' 1981= 198? lees' igsc Castle Complex 325-006 Castle Rock 76,000^" 78,925^"""' 18,690"""" 41,400<'""' 42,515'""' 85,250"""' 39,9%'""" PNC 59363 325-045 Whaler Island ND {0}*""°" ND ND ND ND False Klamath Complex 325-048 RockR {QUKMay)} 0*J»ne) [3"<'°°°'] ND ND ND ND 325-009 Sister Rocks |Qa.l)(M.,)} {30..b 30*""' p^Mjyl ND ND 325-010 False Klamath Rock 16,000^*^ 22,510'""'!" 5,200^)" 10,000"""' 14,000'""' 31301'"^' 15,300""" ND 28,762 Redding Complex 325-013 Redding Rock 500WM»y) 1,275'-'- 1,031 '<'""' l.OSO""^* 650"""" 800""' 700"""' 880*^' ND 780 Trinidad Complex 325-018 Sea Lion Rock |Qa.b(AiipiM) } (0»-W"«>) ND ND ND ND 325-019 White Rock 1,600-^ 1,980"'""' 3028«""" 3,277"""' 2,000'""' 3,055"""" 3,780""' ND ND 325-020 Green Rock 25,000" 32,934""""' {35,000"""-'} 16.960"'""" 21,500"""' 25,155"°'»' 14,000"^' 23,084"°"^' 19,998'""' ND 20,726 325-023 Flatiron Rock 14,650"" 10,600""" 14,500""'>' 14330 "">' 3,500""' 10,757"""' 18,600*^' ND 16,238 325-024 Blank Rock Q».IXJ>il)f) 600^""""' 259<:(Julyl 325"""' 400'""' 3,200'""' 32y*^' ND ND 325-026 Pilot Rock ND 1,538*-""""' 800"""°" 874'<'""'> 1,100"""' 900""' 1,443"""' 1,450""' ND ND Cape Mendocino Complex 325-040 False Cape Rocks 4,661'^«*"»"> 6380"'""" 9,100"-=" 8,619"""' ND ND {2,800""""'} 8,450"""' 9,340""' 11,800""' 325-041 SugarloafRock {O^wjui,)} ND 0 [200"""'] ND ND ND 325-042 Steamboat Rock 2^800^^'"^^ 3,072"'""' 4,000"""' 4,400"""" 3,500""' 4,720"°"' ND ND Vizcaino Complex 379-001 Rockport Rocks j0..w,»«)} ND ND ND ND ND 379-002 Cape Vizcaino y26yWA»e»») 3,500"'""" 3,473"'""" 50i(M.y) 4364"""' 2,720*^» ND ND Newport- -Kibesiliah Complex 379-021 Newport Rocks {0"°~') ND ND 0 ND ND 379-004 Kibesiliah Rock I0-") MMADguslll Qa-b (3"*'-'] ND ND ND ND Goat Complex 379-006 Goat Island Area {©«'• Qi.b(JciJy) ND ND ND ND 110 USGS/BRD/ITR-2000-0012 Table, (continued) Colony Year number Colony name 1979"- 1980""= 1981' 1982° 1985" 1986" Noncomplex locations 379-010 White Rock {0»(June)j Mh(June)1 Qa(July) ND ND ND ND 404-004 Gualala Point Island {0*} {0-1 Ma(Junel] ND ND ND ND Point Reyes Complex' ' 429-001 Point Reyes [Ufi95'"'"'y'] 13,423^'""*' 16,474'""*' 26,337'""*' 9,242 9,360 {9,880'"^'"*'} 18,644'^^'"''>" 34,865'""*' 15,906'""*' Points Resistance-Double Complex 429-024 Point Resistance 2,970»i"'iyi 4 44Qa.b(June) 4^379<--iJ"iyi 1 55QclMayl 3,600'""*' 10,628'""*' 4,100'"-'*' 2,875'""*' 2,255 1,805 429-002 Millers Point Rocks ND 63'""'>" 66'""*' ■ 1 CiMay) ^PTtMay) 0 ND 429-003 Double Point Rocks 3990b(July, gg5flc(Jul,) 7 750'*-"'^""*^' 1^533c(May) 5,875'""*' 13,859'""*' 7,100'""*' 8,650'""*' 3378 1,950 North Farallon Complex 429-05 1 North Farallon Islands ND 31,428""'"" 13 442^ 29,100'""*' 21,550'"'*' 30,914"""*' 30.050'^'""*' {29,940""'""} 18,597 12,780 South Farallon Complex" 429-052 South Farallon Islands ND 52,527"'"'*' 49,975'""*' 61,510'""*' {31,738} {31,101}' {35,928'""''>'} 12.657""'*>' 23,500'""*' 44,250'""*' {33.780)" {31,045}" {SLTSC"""*'} { 30,035"'"""" 1 {45,100"'"'"-") {50,700"'""'=') {30,841}' {30,485') {45,600') {53,550'} {30,716}' Devil's Slide Complex 429-013 San Pedro Rock tka.b (June) ND ND ND ND ND 429-014 Devil's Slide Rock and {1,400''''} 1,750"""*' 800'^"'*' 1,530'""*' ND 0 Mainland 1,000""""''' J^531c(May) /.-^ys*""*' 2,300<""*' [93] Noncomplex location 429-033 Martin 's Beach jQa.b(July)J f Qa.b 454-010 Castle Rocks 954 567 728 841 972 1,439 1,376 and Mainland'' {625') (753') 1,240 (1,445') 454-0 1 1 Hurricane Point Rocks 310 480 365 420 489 496 440 423 Prince Complex 501-004 Prince Island {O") m {0'} {0'} 0 0 0 ' Source is Carter et al. (2000). " Source is Carteret al. (1995). •^ Source is Carter et al. ( 1992). <' Source is Carteret al. (1996). ' For 1989, Carteret al. (1992) accidentally omitted 5,01 1 birds counted at subcolony 02. ' Source is McChesney et al. (1998). * For 1989, Carteret al. (1992) misidentified certain subcolonies in aerial survey data that were combined with boat survey data to derive a total number of murres attending the colony. McChesney et al. ( 1 998) corrected this error and provided a separate aerial survey count of 9,141 birds. However, we used the corrected combined colony total instead of the aerial count alone due to incomplete coverage during the 1989 aerial survey. " For 1 989, Sydeman et al. ( 1 997 : 11 0) reported an incorrect colony total of 23,006 due to a typographical error. In Carter et al. (1996) and elsewhere in Sydeman et al. ( 1 997: 121), the correct total (23,066) is given, which corrects an error found in Carter et al. (1992). For 1990, Sydeman et al. (1997: 1 10) reported a "standardized" colony total of 40,919 birds and a Southeast Farallon Island (SEFI) total of 13,752 birds, by excluding 7 birds at Great Murre Cave. Carter et al. (1996) reported the correct 1990 colony total of 40,926 birds. In 1 994, Sydeman et al. ( 1997: 1 1 0) also reported a "standardized" colony total of 39.773 and a SEFI total of 13,797, by excluding 77 birds at North Landing. In addition, they used incorrect subtotals for West End Island (WEI) ( 1 6,55 1 ), West End Cove (2,309) and Pelican Bowl (5,00 1 ). The correct subtotals are WEI ( 1 6,969), West End Cove (2,752) and Pelican Bowl (4,976). Carter et al. ( 1 996) reported the correct 1 994 colony total of 40.268. ' Source is Sydeman et al. (1997). ' Source is McChesney et al. (1999). BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 1 5 Table, (continued) * For 1989. Carter et al. (1992) reported an incomplete total of 625 murres. by combining highest aerial and ground counts. McChesney et al. (1999) reexamined aerial photographs, omitted ground counts and substituted aerial counts, found and counted a photograph which covered a missing section of the colony, and determined a complete total count of 728 murres. For 1994. Carteret al. (19%) reported a total of 1.435 murres. McChesney et al. ( 1999) reexamined aerial photographs, found and counted an omitted p>hotograph with four additional birds, and determined a total coimt of 1 .439 murres. ' Sources are Ingram (1992): Ingram and Carter ( 1997). ELvtended table legend: Colonies are ordered fh>m iKHth to south. Nonitalicized colonies were attended regularly and breeding is confirmed. Underlined and italicized colony names indicate long-inactive colonies and rocks attended without confumed breeding, respectively. Numbers without brackets refer to total murre counts from aerial photographs. Underlined counts were iiKomplete. Numbers with Ixackets ( [] ) indicate murres attending colonies but breeding not suspected. Braces ( ( ) ) indicate either combined coimts from aerial and ground-boat surveys, ground surveys, or boat surveys. Data considered to be best for trend analyses in this study are indicated in bold font, based on several criteria: ( 1 ) Aerial photograph counts usually fMXjvided higher and better colony numbers than boat and ground counts, except for small areas not photographed. ( 2 ) Surveys duringthemain part of the breeding season (late May to mid-July) were prioritized over earlier or later siu^-eys. (3) Archived raw counts were preferred over back- calculated raw counts. (4) Otherwise less reliable surveys were not used. ItaUcized counts were used to obtain population sums and colony complex totals but were not considered to be comptarable to other data for the colony. Codes: ND. no data obtained: PNC, photographs taken but not counted. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 1 7 Appendix E Population data for common murre (Uria aalge californica) colonies in Oregon, 1987-1995 (prepared by R. W. Lowe) Table. Summary of the total numbers of common murres {Uria aalge californica ) counted from aerial photographic surveys in Oregon in 1 987- 1995 by the U.S. Fish and Wildlife Service. See extended table legend at end of this appendix for format. Colony Colony name Year number 1987 1968 1989 1990 1991 1992 1993 1994 1995 219-001 Unnamed rock ND 8 ND ND ND ND ND ND 0 219-002 Unnamed rock ND 40 ND ND ND ND 7 107 67 219-003 Unnamed rock ND 173 ND ND ND ND ND 7 118 219-005 Tillamook Rock 3,745 5,628 3,654 6,414 6,419 5,732 608 5,484 7,199 219-007 Unnamed rock 0 0 0 0 0 0 0 0 0 219-010 Unnamed rock ND 21 56 112 186 113 0 160 129 219-013 Sea Lion Rock ND 1,602 1,912 1,761 ND 2,188 546 2,144 2,694 219-014 Unnamed rock ND 18 27 29 ND 56 7 43 130 219-017 Bird Rocks N ND 2,798 2,462 2,902 2,480 2,697 151 2,335 3,145 219-018 Bird Rocks W ND 19,250 ND ND ND ND ND ND ND 219-019 Bird Rocks SC ND 5,610 6,034 ND ND ND ND ND 7,143 219-026 Castle Rock ND 6,893 ND ND ND ND ND ND 6,132 219-027 Gull Rock ND 3,960 ND ND ND ND ND ND 5,342 219-029 Cape Falcon NF ND ND ND ND ND ND ND ND ND 219-030 Cape Falcon Rock ND 6 0 0 ND ND ND ND ND 219-036 Unnamed rock ND 0 0 0 0 0 0 Pr 43 219-044 Pyramid Rock ND 5,940 ND ND ND ND ND ND 4,926 219-045 Pillar Rock ND 6,645 ND 6,229 6,895 6,196 0 5,302 7,079 219-047 Cape Meares NPNF ND 20 ND ND ND ND ND ND ND 219-048 Cape Meares NP ND 20 ND ND ND ND ND ND ND 219-049 Cape Meares NPSF ND 5 ND ND ND ND ND ND ND 219-050 Cape Meares NC ND 70 ND ND ND ND ND ND ND 219-051 Cape Meares NF ND 13 ND ND ND ND ND ND ND 219-054 Finley Rock ND 28,224 ND ND ND ND 0 ND ND 219-055 Middle Rock ND 23,842 ND ND ND ND 0 ND ND 219-056 Shag Rock ND 79,415 ND ND ND ND 0 ND ND 219-057 Seal Rock ND 0 157 68 99 0 0 0 0 219-060 Brown Rock 1,013 1,473 2,506 1,494 2,117 2,315 0 2,278 1,922 219-061 Cape Lookout NF ND 163 ND ND ND ND ND ND ND 219-062 Cape Lookout WF ND 90 ND ND ND ND ND ND 132 219-063 Cape Lookout SF ND 8,031 ND ND ND ND ND ND ND 219-068 Cascade Head (Mnld) ND 110 97 ND ND ND 0 ND ND 219-069 Unnamed rock ND 2,158 2,069 ND 2,170 2,008 753 2,207 2,772 219-070 Unnamed rock ND 972 622 649 741 870 306 900 773 219-071 Unnamed rock ND 970 632 801 567 443 134 571 777 219-072 Two Arches Rock ND 12,176 15.982 ND ND 14,265 ND ND ND 219-073 Unnamed rock ND 8,400 ND ND ND ND ND ND ND 243-010 Gull Rock ND 13,730 14,219 14,377 12,243 11.704 8,651 11,278 13,013 243-015 Colony Rock 12,473 14,134 19,147 18,668 14,423 14,787 8,795 13,752 15,440 243-015A Subcolony Rock 0 0 0 75 56 33 0 6 73 243-016 Yaquina Head (Mnld) 0 0 0 0 0 0 168 119 265 243-017 Flat Top Rock 0 0 0 8 192 603 783 1,201 1,692 270-015 N. Coquille Pt. Rock ND 6,194 ND 6,647 ND 6.440 ND ND ND 270-016 M. Coquille Pt. Rock ND 0 0 0 5 17 0 107 90 270-017 Unnamed rock ND 0 0 46 324 795 204 1,180 1,079 270-019 Cat and Kittens ND 20,403 23,220 ND ND 22,917 ND ND ND 270-020 Face Rock ND 3.198 ND ND ND ND ND ND ND 270-023 Tower Rock ND 1,011 ND ND ND ND ND ND ND 118 USGS/BRD/ITR-2000-0012 Table, (continued) Colony Colony name Year number 1987 1988 1989 1990 1991 1992 1993 1994 1995 270-025 Unnamed rock NO 300 ND ND ND ND ND ND ND 270-027 Gull Rock ND 24,057 ND ND ND ND ND ND ND 270-029 Best Rock ND 15,405 ND ND ND 13,988 ND ND ND 270-032 Square White Rock ND 4,016 ND ND ND 4,110 ND 4,961 ND 270-034 Conical White Rock ND 2,051 1,775 1,883 2,149 1,310 793 2,317 1,737 270-035 West Conical Rock ND 1,161 ND ND ND 625 ND 922 ND 270-036 Arch Rock ND 69 ND ND ND 89 ND ND ND 270-043 Redfish Rocks N 1,564 1,399 1,398 1,888 1,521 1,841 197 1,514 1,244 270-044 Redfish Rocks NC ND 816 738 859 666 710 32 1,074 733 270-045 Redfish Rocks EC ND 5,017 ND ND ND ND ND ND ND 270-046 Redfish Rocks SC ND 1,771 ND ND ND ND ND ND ND 270-047 Redfish Rocks S ND 4,268 ND ND ND ND ND ND ND 270-048 Unnamed rock ND 2,091 ND ND ND ND ND ND ND 270-049 Island Rock ND 12,865 ND ND ND ND ND ND ND 270-063 Hubbard Mound Rock 14,731 13,091 ND ND ND ND ND ND ND 270-064 Dog Rock 2,043 2,026 2,207 2,087 2,389 1,579 1.729 2,004 1,732 270-067 Double Rock ND 519 ND ND ND ND ND ND ND 270-068 Needle Rock ND 1,884 2,070 ND 2,102 1,202 0 2,138 2.336 270-085 Unnamed rock ND 44 59 72 75 64 54 88 142 270-086 Unnamed rock ND 327 87 90 85 65 50 164 61 270-087 Mack Arch ND 13,839 ND ND ND ND ND ND ND 270-110 Unnamed rock ND 24,316 ND ND ND ND ND ND ND 270-115 Twin Rocks E 1,225 1,006 ND ND ND ND ND ND ND 270-116 Twin Rocks W 7,422 5,023 6,959 6,400 7,588 4,147 2,199 6,292 6.017 270-117 Unnamed rock ND 1,810 1,918 1,657 1,340 748 528 1,497 1,521 270-122 Unnamed rock ND 820 676 768 576 474 223 701 618 270-123 Goat Island 2,616 2,873 2,896 2,968 2,584 2,219 918 2,835 2,910 Extended table legend: Colonies are ordered from north to south. Nonitalicized colonies were attended regularly and breeding is confirmed. Bold colony numbers and names indicate sample colonies used for trend analyses from 1988 to 1995. Italicized colony numbers and names indicate rocks attended without confirmed breeding. Codes: ND, photographs taken but not counted or no photos were taken; Pr, murres present. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 1 9 Appendix F Population data for common murre (Uria aalge califomica) colonies in Washington, 1979-1989 (prepared by U. W. Wilson) Table. Summaiy of the total numbers of common murres [Una aalge califomica] counted from aerial photographic surveys conducted in Washington in 1979-1989 by the U.S. Fish and Wildlife Service. See extended table legend at end of this appendix for fomiat. Colony Year number Colony name 1979 1980 1981 1982 1983 19B* 1985 1986 1987 1988 1989 Point Grenville Complex 586 Erin 1^75 1.175 250 1.735 320 150 50 800 0 80 150 585 Erin's Bride 675 730 200 790 590 250 250 800 250 75 0 584 Unnamed rock 0 0 0 0 0 0 0 0 0 0 175 575 Grenville Arch' 8.985 5.825 3.250 5.015 0 0 50 15 5.050 250 75 570 Radio Stack 1.550 1.690 UOO 1.115 0 650 0 0 200 300 650 Split->Mlloughby Complex 531 Split R(ick^ 9.150 3.075 8.350 10.450 0 0 100 0 450 50 75 529 WilloughbyRcck' 5.300 3.115 3.800 5.270 850 0 0 40 0 35 200 Other Locations 480 Destruction Island *' 0 0 0 0 0 0 0 0 0 300 250 458 Middle Rock 0 0 0 0 0 0 1.800 450 0 0 0 457 North Rock NS NS NS NS NS 0 0 15 0 0 0 426 Unnamed rock NS NS NS NS NS 0 0 10 0 0 0 419 Unnamed rock NS NS NS NS NS 0 0 0 20 0 0 409 Rounded Island 2,130 3.435 850 2.180 200 800 300 0 0 0 0 Qniila>iite Needles Complex 367 Unnamed rock NS NS NS NS NS 0 10 0 0 0 0 363 Table Rock 210 275 250 320 30 0 175 50 0 450 150 361 Huntington Island ' 895 630 0 0 0 0 0 250 ZOOO 1.600 1.400 361 A Cakesosta' 450 685 50 580 0 0 0 150 370 600 250 355-359 Unnamed rocks >> NS NS NS NS NS 0 0 0 0 0 100 333 Gunsight Rock NS NS NS NS NS 0 0 50 50 0 0 332 Petrel Island 480 1.600 0 855 1.200 620 0 350 1.480 0 0 317 Cake Rock NS NS NS NS NS 0 0 0 0 0 0 Carroll-Jagged Complex 294 Unnamed rock NS NS NS NS NS 0 2 0 0 0 0 269 CarroU Pillar NS NS NS NS NS 0 0 0 0 0 0 262 Carroll Island' 0 0 0 0 0 0 0 0 0 0 0 258 Jagged Pillar 0 0 0 0 0 0 0 0 0 0 0 256 Jagged Island " 0 0 155 0 0 0 655 0 800 450 450 Other Locations 192 White Rock 120 0 0 630 0 0 0 0 55 0 0 140 Unnamed rock NS NS NS NS NS 0 0 125 0 0 0 Tatoosh Complex 35 Tatoosh Rock NS NS NS NS NS NS NS NS NS NS NS 23 Tatoosh Rock NS NS NS NS NS NS NS NS NS NS NS 22 Tatoosh Rock NS NS NS NS NS NS NS NS NS NS NS 21 Tatoosh Island ' NS NS NS NS NS NS NS NS NS NS NS ' Breeding has been confirmed with observations of eggs or chicks. '' These locations lacked suitable tMceding habitat Extended table legend: Colonies are ordered from south to north. Nonitalicized colonies were attended regulariy and breeding is expected. Italicized colonies indicate rocks with murre attendance in less than 4 years or no suitable breeding habitat. Codes: NS. site not aerially surveyed by the U.S. Fish and Wildlife Service. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 21 Appendix G Population data for common murre {Una aalge californica) colonies in Washington, 1990-1995 (prepared by U. W. Wilson) Table. Summafy of the total numbers of common murres {Uria aalge californica] counted from aerial photographic surveys conducted in Washington in 1990-1995 by the U.S. Fish and Wildlife Service. See extended table legend at end of this appendix for format. ^ Year Colony 1994 1 199S i" number Colony name 1990 1991 1992 1993 6/16 7/5 6/19 6iG5 7/13 7/27 Point Grenville Complex 586 Erin 125 25 75 45 230 175 110 0 no 55 585 Erin's Bride 0 50 75 70 190 130 395 35 105 80 584 Unnamed rock 0 0 0 0 0 0 0 0 0 0 575 Grenville Arch >= 850 25 50 15 25 85 0 0 0 0 570 Radio Stack 0 350 350 250 75 220 0 0 605 5 SpUt-WUloughby Complex 531 Split Rock' 0 150 0 0 15 0 0 0 170 70 529 WilloughbyRock' 15 75 0 0 0 0 0 0 35 0 Other Locations 480 Destruction Island" 250 650 350 0 0 0 0 0 0 215 458 Middle Rock 0 0 0 0 0 0 0 0 0 0 457 North Rock 0 0 0 0 0 0 0 0 0 0 426 Unnamed rock 0 0 0 0 0 0 0 0 0 0 419 Unnamed rock 0 0 0 0 0 0 0 0 0 0 409 Rounded Island 0 0 0 0 0 0 0 0 0 0 Quillayute Needles Complex 367 Unnamed rock 0 0 0 0 0 0 0 0 0 0 363 Table Rock 350 350 175 0 550 375 0 0 0 0 361 Huntington Island ' 1,050 550 1,500 0 1,660 1,265 2,480 2,460 2,590 1,755 361 A Cakesosta' 450 300 295 0 370 10 590 815 950 605 355-359 Unnamed mcks " 360 250 150 0 150 15 280 225 205 140 333 Gunsight Rock 35 0 15 25 0 55 50 45 100 70 332 Petrel Island 0 0 0 5 40 15 0 50 80 75 317 Cake Rock 175 0 25 0 0 0 0 0 0 0 Carroll-Jagged Complex 294 Unnamed rock 0 0 0 0 0 0 0 0 0 0 269 Carroll Pillar 0 0 0 45 0 120 375 345 430 455 262 Carroll Island' 0 0 0 75 0 95 815 1,275 1,260 1,025 258 Jagged Pillar 0 25 0 0 0 0 0 0 0 0 256 Jagged Island ' 250 500 250 0 0 125 0 0 0 0 Other Locations 192 White Rock 450 175 175 0 350 110 110 5 0 85 140 Unnamed rock 0 0 0 0 0 0 0 0 0 0 Tatoosh Complex 35 Tatoosh Rock NS NS NS NS NS 0 165 190 190 200 23 Tatoosh Rock NS NS NS NS 490 360 660 0 355 925 22 Tatoosh Rock NS NS NS NS 0 130 110 70 60 60 21 Tatoosh Island' NS NS NS NS 585 260 550 220 285 520 ' In 1994, two surveys were conducted on 16 June and 5 July. '' In 1995, four surveys were conducted on 19 and 25 June and 13 and 27 ' Breeding has been confirmed with observations of eggs or chicks. '' These locations lacked suitable breeding habitat. July. Extended table legend: Colonies are ordered from south to north. Nonitalicized colonies were attended regularly and breeding is expected. Italicized colonies indicate rocks with murre attendance in fewer than 4 years or no suitable breeding habitat. Codes: NS, site not aerially surveyed by the U.S. Fish and Wildlife Service. BIOLOGY AND CONSERVATION OF THE COMMON MURRE 1 23 Appendix H Summary of regression analyses (prepared by J. L. Yee and H. R. Carter) We conducted the following three types of regression analysis: (1) Simple linear regression to demonstrate major trends in the log-transformed annual sums of whole-colony counts for populations of common murres (Uria aalge califomica) in central California, northern California. Oregon, southern Washington, northern Washington, and Washington (referred to as "'Sum Regressions"); (2) Poisson Regression to demonstrate major trends in annual sums of whole-colony counts for colony complexes in central California and Washington: and (3) Averaged Poisson Regressions for colony complexes over a certain period within central California to derive "Route Regressions'" for comparison with Sum Regressions over the same period (Geissler and Sauer 1 990: Link and Sauer 1994). For either regression method (Sum Regression or Route Regression), trends can be fit with Poisson Regression directly on counts or simple linear regression on log- transformed counts. Both approaches fit a linear relation between time and population size on a log-scale, allowing percent per annum change to be derived from the exponent of the slope of log(N). Further, the log- transformation helps the data to better meet the constant variance assumption of simple linear regression (Rawlings 1988; Neter et al. 1990). Both approaches provide consistent results when counts are large. However, they differ in assumptions regarding the distribution of errors in the model and there are problems in the simple regression approach when counts are too close to zero. We chose to use simple linear regression on the log-scale for the Sum Regression method since it is a more accessible approach and the data sums involved were large enough to make the two approaches comparable. The Poisson Regression was selected for the Route Regression method because some individual colony complex counts reached zero. To examine possible violation of independence in using a series of years of available data for regression analyses, we performed Durbin- Watson tests (Durbin and Watson 1 950, 1 95 1 ) but did not find evidence of autocorrelation. All regressions were performed using SAS 7 (SAS 1997). and graphs were prepared using Microsoft Excel 97. With regard to the practical application of linear regression techniques, we have not assumed that true linearity exists in the data examined since different results can be obtained by merely considering slighdy different samples of years. A wider class of models able to reflect nonlinear relations between population size and time would produce better fitting models but. for our objective, this exercise probably would produce needlessly complex models. We instead used the approach that reasonable line approximations to nonlinear functions can be taken over subset ranges of data. To standardize the use of regression analyses in this chapter, we conducted regressions over three time periods (1) data throughout the 1979-95 period that used all years of standardized whole-colony count data when all colonies were surveyed: (2) a subset of population data confined roughly to the first half of this period (i.e., between 1979 and 1989) with a consistent trend of decrease, increase, or no change during this period; and (3) a subset of population data confined roughly to the second half of this period (i.e., between 1984 and 1995) with a consistent trend of decrease, increase, or no change. Subsets were based on trends evident from inspection of sums of whole-colony counts. For Poisson and Route Regressions of colony complexes, the same range of years of data was applied (as for Sum Regressions of the larger population), but additional years of data for colony complexes were included if available. All regressions were presented in tables. To perform Sum Regressions, we collated populadon sums for each geographic area from available data in Appendixes C. D. E. F. and G. Population sums are summarized in Table H- 1 , including sums for ( 1 ) all colonies in central California between 1980 and 1995; (2) all colonies, except Castle Rock, in northern California between 1979 and 1989; (3) 15 sample colonies in Oregon between 1988 and 1995: (4) all colonies in southern Washington between 1979 and 1995: (5) all colonies, except Tatoosh Island and associated rocks, in northern Washington in 1979-95; and (6) all colonies, except Tatoosh Island and associated rocks, in Washington between 1 979 and 1 995. The regressions were conducted by examining the relation of N on year where A' is the sum of whole- colony counts for all colonies (or all sample colonies) in a geographic area. To describe Sum Regressions for three time periods, we presented in Table H-2 ( 1 ) the slope of ln(^ with standard error and 95% confidence limits; (2) the percent per annum change, with 95% 124 USGS/BRD/ITR-2000-0012 confidence limits; (3) the H value; and (4) the p-\a\ue for testing whether the slope was statistically different from zero. In Figures 2.4, 2. 1 0, and 2. 1 2, Sum Regression lines are indicated for trends that were statistically different from zero at the 0.05 significance level. To perform Poisson Regressions, we summed available data from individual colonies within colony complexes in central California and Washington from Appendixes C, D, F, and G (Tables H-3 and H-4). The regressions were conducted by examining the relation of A^ on year where A' is the sum of whole-colony counts for all colonies in a colony complex, and using the deviance to adjust the standard errors for overdispersion (McCullagh and Nelder 1989; SAS 1997). We described Poisson Regressions for three time periods by presenting in Tables H-5 and H-6: (1) the slope of InCAO for each colony complex with standard error and 95% Bonferroni simultaneous confidence limits; (2) the percent per annum change for each colony complex, with 95% Bonferroni simultaneous confidence limits; (3) the Bonferroni-adjusted p-values for testing whether the slopes were significantly different from zero (Westfall and Young 1993); and (4) results of testing for differences between trends for different colony complexes. In Figures 2.3 and 2. 1 1 , Poisson Regression lines are indicated at colony complexes with trends that were statistically different from zero at the 0.05 significance level under Bonferroni adjustments for simultaneous inference across colony complexes in central California and Washington. We performed Route Regressions by taking the averages of percent per annum changes from Poisson Regressions for colony complexes within geographic areas (weighted by population size and survey effort). Standard errors were obtained by bootstrap (Efron and Tibshirani 1993). Both Sum Regression and Route Regression methods aim to estimate trends for geographic areas. However, Route Regression better accounts for between-site variation in trends when study sites are randomly sampled, thus often producing a more reliable test and confidence interval for trend, but does not produce an estimate of intercept. In Table H-7, we compared trends depicted with Sum Regressions and Route Regressions in central California, which helped to assess the general consistency of the Sum Regression methods used to derive population trends for central California. 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Disn Held Siaicn. 6924 Tiemon Road Dixoa California 95620 a FBfORMNG CRGAMZATION a SPONSQHMVMMTOHNG AGBO NA**ISI AND ADOflESSESI U.S Geok^cd Siivey. Wesan Ec<4ogical Research Ceiaa^. 7801 Fblsam Boule\3(L Suite 101. Sacomeiaoi, Olilbnia 95K76 U.S. Ffeh and wajife Service, Division of NSgratory Bird Mani^einenl, 91 1 ItE 11* Avenue. Pbttlml Oregon 97232 10 SPONSOHlNGtiMQNITaHNG AG0CYHtHJHINlA«B1 Information and Technology ReponiUUMWP II. SUPna€NTAffir NOTES 12a OBIfflBUnON^AVAiyVHUTY STATaeff Release inbniied. AvaibUe fiom National Technical brfatnuian Service. 5285 Pbn Roy-al Riwl Sprii^field. VA ^161 (1-80O-5531-6S47 or 703-I87-»650) i2hDeTHHniGNnnrF U AISIH«CT(IUbnnjn2inwcnlsl Iv iIk paa 30 ycatv die coinnan nure ( Uria oof^ aa<{|br7Bca 1 has been iai)gni2ed as a pianiien indict V/KUiffin. aid British Cohortiia. espedafly impacts bom oil poUutian. oeitain fisheries, and bunan dututance. To assist die effective matE^einent of die cannon aaae and die marme envnonmens in »tich diev bve. das suimao of available informatian on die hmloEy and regional staus of die commn muire has been sponsored l9dieU.S. Hsh aid >V'iidlife Service (Dnision of Ntgraory Bird. Man^emea). In Vokime 1 (Chapter li.dienaiuralfai$toc> of die common nuie is sunmaiized. (kavkmg heavily on bteecii^ smcfies 6oin the South I^raDon Islands. California, phis a host of delaikd faieecing siudks hom die North .Ailanic Oceai. Ripulaiion nends of die common nure ate summarized in Volume I iChapKr 2). focusing on charges in whole