Vol. 16, No. 1, 1985 WESTERN BIRDS Quarterly Journal of Western Field Ornithologists President: Laurence C. Binford, 985 Emily Avenue, Rohnert Park, CA 94928 Vice-President: Tim Manolis, 3532 Winston Way, Carmichael, CA 95608 Treasurer/ Membership Secretary : Garth Alton, 17 Camino Lenada, Orinda, CA 94563 Recording Secretary: Jean-Marie Spoelman, 4629 Diaz Drive, Fremont, CA 94536 Circulation Manager: Jerry R. Oldenettel, 4368 37th Street, San Diego, CA 92105 Directors: Laurence C. Binford, Peter Gent, Virginia P. Johnson, John S. Luther, Guy McCaskie, Timothy Manolis, Narca Moore-Craig, Joseph Morlan, Janet Witzeman Editor: Alan M. Craig, P.O. Box 254, Lakeview, CA 92353 Associate Editors: Cameron Barrows, Tim Manolis, Narca A. Moore-Craig, Dale A. Zimmerman Layout Artist; Virginia P. Johnson Photo Editor: Bruce Webb, 5657 Cazadero, Sacramento, CA 95822 Review Editor: Richard E. Webster, P.O. Box 6318, San Diego, CA 92106 Editorial Board: Robert Andrews, Alan Baldridge, William H. 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If this is not possible, extra charges for typesetting will be made as follows; $15 full page, $l0halfpage, $5 quarter page. Send copy with remittance to the Treasurer. Make checks payable to Western Field Ornithologists. A 15% commission is allowed for agencies. WESTERN BIRDS Volume 16, Number 1, 1985 THE BREEDING AVIFAUNA OF SAN BENITO MOUNTAIN, CALIFORNIA: EVIDENCE FOR CHANGE OVER ONE-HALF CENTURY NED K. JOHNSON, Museum of Vertebrate Zoology and Department of Zoology, University of California, Berkeley, California 94720 CARLA CICERO, Department of Landscape Architecture, University of California, Berkeley, California 94720 The San Benito Mountain region of the southern Diablo Range, San Benito and Fresno counties, California, is of unusual biological interest for several reasons. The highest peaks, San Benito Mountain (5241 ft [1599 m]) and Santa Rita Peak (5165 ft [1575 m]), support on their upper slopes significant forest well isolated from such growth in other areas. The nearest major stands of mixed conifers appear approximately 50 miles (80 km) to the west, in the northern Santa Lucia Range, Monterey County. Eastward, a distance of approximately 93 miles (150 km) separates the San Benito con- ifers from the rich forests of the Sierra Nevada (Figure 1) . The dominant species of conifer in most of the forest is Coulter Pine (Pinus eoulteri). It hybridizes extensively with the much scarcer Jeffrey Pine ( Pinus jeffreyi ) , the latter species growing in strongly disjunct stands far from its main Sierran distribution (Griffin and Critchfield 1976:82). Digger Pine ( Pinus sabiniana) and Incense-cedar ( Calocedrus decurrens ) are also prevalent. Ac- cording to Griffin (1974: 13) , “the combination of these three related pines all growing together can not be duplicated anywhere else and is of great interest to forest geneticists.” Strangely, much of the forest grows in open and highly insolated stands which are largely confined to otherwise bald serpentine soils (Figure 2). A diverse group of shrubby species also forms a conspicuous chaparral element on the serpentine. However, most of these shrubs are not those usually associated with montane forest. In addition, the serpentine soils support an interesting assemblage of herbaceous species, some of which are endemic. The foregoing floristic notes are mainly from Griffin (1974 and 1975). He also fully describes other aspects of the local ecology. Western Birds 16:1-23, 1985 1 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN Although the San Benito Mountain area has been easily accessible for years and received concentrated attention from at least two groups of vertebrate zoologists prior to our visits in 1983 and 1984, only scattered bird records from there have been published (Grinnell and Miller 1944). Our survey of American Birds for the last decade turned up no recent records for the region. Insofar as we have been able to ascertain, the notes and specimens taken by all previous workers are preserved in the Museum of Vertebrate Zoology, University of California, Berkeley. The first major sample of birds from the region was taken by Fletcher G. Palmer between 9 and 21 June 1936. He was accompanied by David H. Johnson, who mainly col- lected mammals. Camping at 4400 ft (1342 m) , 1 mile (1.61 km) southeast of the San Benito Mountain summit, they collected primarily on the moun- tain but also visited nearby Santa Rita Peak. Importantly, their work was done during the heart of the breeding season. Eight years later, from 6 to 11 August 1944, Alden H. Miller and Robert W. Storer collected a large number of birds and other vertebrates from much of the highland area surrounding San Benito Mountain as well as from the peak itself. Although their August records are too late to document breeding status for the summer resident species, they are suitable as evidence for the occurrence of permanently resi- dent forms. Our work in 1983 (12-14 May and 8-9 June) and 1984 (12-18 May and 31 May-1 June) focused on the densest stands of conifers on San Benito Mountain, those occurring on north and northeast -facing slopes and draws between 4000 ft and the summit. On 17 May 1984, we censused species found along a 3- mile transect following San Carlos Creek, from 3700 ft (1129 m) to 4400 ft. We also hiked the lower canyon of the East Fork of San Carlos Creek, which differs from much of the area in that it is relatively moist and dominated by Canyon Live Oaks (Quercus chrysolepis) . Despite the fact that our work emphasized the mid -May period, we stress that nesting behavior and reproductive condition of collected specimens clearly estab- lished breeding status for the vast majority of birds present at that time. Sur- prisingly few birds seem to use San Benito Mountain as a stop-over site dur- ing migration. Our studies, as well as those conducted by earlier field parties, are supported by complete and annotated lists of every species encountered in the region. Although we do not consider such compilations to be ex- haustive lists, they are complete enough to support the discussion and con- clusions on avifaunal change offered beyond. Coniferous forest in the North Temperate Zone is occupied largely by a boreal avifauna. According to Miller (1951:582-591), such an avifauna in California is comprised of species of fundamentally northern derivation that range into boreal environments of the state, either along the coast or in the highlands. In general, such species are adapted to cool and/or moist habitats. As Miller has mapped (loc. cit.:588), boreal environments along the coast of west-central California are fragmented into two components, Santa Cruz and Monterey: these are positioned north and south of Monterey Bay, respectively. The coniferous forest of San Benito Mountain represents a boreal island lying approximately 50 miles to the east of Miller’s Monterey component (hereafter called “the Monterey District”). For one or more reasons, Miller did not include the San Benito Mountain region on his map of the boreal areas of California. First, perhaps he regarded it as one of an 2 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN unspecified number of “very small detached boreal areas” which were neither plotted nor analyzed (Miller 1951:583). Second, he may have con- sidered the region to have been incompletely explored avifaunally. Third, he had not personally visited the mountain during the breeding season. In any event, despite the small size, isolation and impoverishment of the boreal en- vironments of the San Benito Mountain region, a substantial mountaintop avifauna occurs there. The first purpose of our paper is to describe this avi- fauna and to compare it with disjunct boreal avifaunas to the west, namely those of the Monterey District and Hastings Natural History Reservation, and with a more remote boreal avifauna to the east, that of Yosemite National Park in the main Sierra Nevada (Figure 1} . The avifauna of San Benito Mountain deserves special attention for another reason. Because of the thoroughness of the surveys, it is possible to search for evidence of temporal change over the approximate V 2 century that elapsed between the early and recent visits. This is the second purpose of our Figure 1 . Map of central California showing the location of the San Benito Mountain region in relation to the Monterey District as defined by Miller (1951), the Hastings Natural History Reservation, and Yosemite National Park. 3 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN paper. As the following species accounts will show, some surprising changes have indeed occurred, both in the composition of the avifauna and in the abundance of certain breeding species. Although the emphasis of this paper is on boreal species, accounts are also included for austral forms that have either colonized or changed in status within recent decades. Furthermore, we also comment on interesting habitat relationships for particular species. SPECIES ACCOUNTS MOUNTAIN QUAIL (Oreorfyx pictus) . Although well-known from the Santa Lucia Range of Monterey Co., this species was not reported from the San Benito Mountain region by Grinnell and Miller (1944:117-119). Thus, Palmer did not record it during his work there in 1936. In contrast, we heard Mountain Quail commonly in 1983, when several widely-spaced individuals were calling on each of several mornings. In May 1984, the species was again recorded but less frequently. Evidently, these in- dividuals were descendants of 43 birds introduced above New Idria in 1957, from stock native to the China Lake region [probably from the nearby Argus Mountains] ( fide Don Pine of California Department of Fish and Game, J.R. Griffin in litt. 10 Jan 1984). There is no evidence that Mountain Quail ever occurred naturally on San Benito Mountain, although the extensive habitat of diverse brushland there seems ideal for this species. Figure 2. View of the high country, looking north, from the north slope of San Benito Peak, 8 June 1983. Note the open nature of the forest, small stature of the trees, and the prevalence of bare serpentine soil. The track of a dirt bike is visible in the left-center of the foreground. Photo by Carla Cicero 4 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN NORTHERN SAW- WHET OWL ( Aegolius acadicus). At 0250 on 18 May 1984, we awoke to the rhythmic whistles of this species coming from the forest approximately 400 yards above camp along the East Fork of San Carlos Creek, 4500 ft (1373 m) (at Viz mile north and Vz mile east of San Benito Mountain). The night was clear and cool (Temp. 50 °F) with a gibbous moon. In response to our imitations of the call, the owl moved upslope for Vz mile before finally taking a stand in a clump of young Incense- cedars just below the peak. Surrounding this steep site were scattered yellow pines (P. coulteri and/ or P. jeffreyi) and a broken understory of Leather Oak (Quercus durata ) . We approached within 8 ft, and with a dim flashlight watched it call continuously for 8 minutes from the same perch. These calls fluctuated in amplitude, giving the false im- pression that the owl was changing perches. After departing for approximately 10 minutes, it returned briefly to the same nearby perch and then moved laterally along the slope for several hundred yards. It was not followed further. In view of the behavior and habitat of this individual, we do not hesitate to include the Northern Saw-whet Owl among the probable breeding species of the region. HAIRY WOODPECKER (Dendrocopus uillosus hyloscopus) . All ornithologists who have visited the San Benito Mountain region have encountered this woodpecker in the coniferous forest near San Benito Peak. Palmer recorded four to five individuals at 1 mile southeast of San Benito Mountain, 4400 ft. between 9-22 June 1936; during that period, he collected two adult males (testis 4x2 mm) and one juvenile male. Miller and Storer also noted several Hairy Woodpeckers at the same locality on 6-12 August 1944. In 1983 and 1984, this species was found regularly in the conifers sur- rounding the summit. One or two birds were recorded daily, including several pairs, and, on 16 May 1984, a pair was observed in courtship behavior. Therefore, a small breeding population still thrives in the San Benito Mountain region. No change in historical status is indicated. OLIVE-SIDED FLYCATCHER (Contopus borealis ). Palmer (MS) stated in June 1936 that he saw Olive -sided Flycatchers “fairly regularly” in the conifers. He took a male in breeding condition (testis 8x3 mm) on 10 June. Miller and Storer also reported the species in August 1944, but the individuals at that season could have been early migrants. In 1983 and 1984, this species was surprisingly numerous on San Benito Mountain, with 5-15 males singing on a single day; 14 regularly -spaced singing birds were encountered along our 3- mile transect. One male was taken (testis 11x4 mm, no fat) on 13 May 1984 along San Carlos Creek, 4400 ft. These records indicate that the Olive -sided Flycatcher has probably increased in population size between 1936 and 1983-1984. WESTERN WOOD-PEWEE (Contopus sordidulus). This species has definitely in- creased in numbers on San Benito Mountain in recent decades. Palmer (MS) reported the Western Wood-Pewee as “not common in the conifers” in June 1936. Storer (MS) noted that the species was “seen in the trees around camp and down the stream from camp” between 6-12 August 1944. He took an adult male (testis 3.5 mm; “little” fat) on 10 August at 4400 ft; this individual may have been a locally breeding bird. In contrast, the species was abundant on the mountain in 1983 and 1984. We recorded 6 to 8 individuals on 13 May 1983, approximately 20 territorial males in the conifers during the morning of 9 June 1983, and 34 singing and chasing males along the 17 May 1984 transect. One breeding male (testis 6 x 3.5 mm, no fat) was collected on 16 May 1984 at San Carlos Creek, 4400 ft, and on 1 June an active nest was found in a Coulter Pine near the same creek. DUSKY FLYCATCHER (Empidonax oberholseri) . The Dusky Flycatcher had not been recorded as a definite summer resident in the San Benito Mountain region before our visits in 1983 and 1984. Now, a substantial population occupies the mountain, and up to 10 individuals have been found singing on territories in a single day. On 8 5 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN June 1983, a singing male in breeding condition (testis 7x3 mm, no fat) was taken. Miller and Storer’s specimen (testis 2 mm) from the area was not taken until early August (1944), and thus provides equivocal evidence for local nesting. Palmer (MS) did not mention the species. During our visits, these flycatchers inhabited mixed yellow pines and Incense -cedars with clumps of Arctostaphylos and oak brush always nearby. A chaparral or low thicket element seems crucial for nesting wherever the species occurs (Johnson 1963) . The nearest probable breeding locality for the Dusky Flycatcher occurs to the west at Chews Ridge, Monterey Co,, where singing individuals have been found during late spring and summer in recent years (Chandik and Baldridge 1969; DeSante and LeValley 1971). Prior to these reports, the closest breeding sites included the Mt. Pinos area of Ventura Co, to the south and the higher elevation habitat in the Inner Coast Range of Lake Co. to the north. GRAY FLYCATCHER ( Empidonax wrightii). This species is well-known as a summer resident in eastern California. It occurs on the Modoc Plateau, in Mono and Inyo counties (Johnson 1963 and 1966), and throughout the higher mountains of the Mohave Desert (Johnson and Garrett 1974:47, Cardiff and Remsen 1981). Locally, it also breeds on the east slopes of the mountains of southern California (Garrett and Dunn 1981, Weathers 1983). Furthermore, a substantial population occurs in the Chimney Peak area of eastern Tulare Co. (Johnson and Garrett 1974:47). In 1983 and 1984, we found a population of summer resident Gray Flycatchers in the open conifers of San Benito Mountain. One singing male was taken (testis 5x3 mm, no fat) on 8 June 1983, Vz mile east of the summit, 4800 ft (1464 m); two others were col- lected (13 May, 6x3 mm; 1 June, 7x3 mm) in 1984, 1 mile southeast of the peak, 4400 ft. These birds were patrolling territories in well-spaced Incense-cedars and yellow pines, 2-2.5 ft (0.6-0. 8 m) in diameter and 20-25 ft (6-8 m) in height, with a scattered understory of scrub oak and manzanita (Figure 3). Much of the ground was bare, an apparent habitat requirement of this flycatcher (Johnson 1963). Several other individuals were encountered in similar habitat on 9 June 1983, and daily during our work in May 1984. We counted seven birds along our 3-mile transect on 17 May 1984, five of which were males singing repeatedly from small pines and Incense - cedars near the road; the remaining two birds, as well as one seen near Sawmill Creek on 13 May 1984, were probable females that occurred with males nearby and which behaved excitedly at our presence. Importantly, the males were singing in the same areas during our visits in both mid-May and early June 1984, Although no nests were found, the evidence strongly indicates that the flycatchers were established for breeding. This surprising occurrence extends the probable nesting range of the species approximately 150 miles (240 km) westward from the principal breeding distribution on the east side of the Sierra Nevada. WESTERN FLYCATCHER ( Empidonax difficilis). Breeding sites for this species are widely scattered in the generally dry Inner Coast Range of central California (Johnson 1980). Palmer took a breeding male (testis 5 x 2.5 mm) of £, d, difficilis at 1 mile southeast of the summit of San Benito Mountain, 4400 ft, on 13 June 1936. Miller (MS) reported a family group with short- tailed young in the conifers on 6 August 1944. In 1984, we collected a mated pair of Western Flycatchers (male, testis 5x3 mm, no fat; female, ova enlarged, ovary with 2 collapsed follicles, active incubation patch) along the East Fork of San Carlos Creek, 4200 ft. The male was delivering position notes from Canyon Live Oaks and the female was repeatedly uttering alarm notes at our presence, suggesting a nearby nest. The moist, steep -sided canyon of the East Fork, with large oaks shading a small, boulder-studded stream, provided ex- cellent nesting habitat. Such habitats are very local in the region, however, and thus the San Benito population of Western Flycatchers is probably sparse at best. The records indicate no change in historical status. 6 AV1FAUNAL CHANGE ON SAN BENITO MOUNTAIN PURPLE MARTIN (Progne subis) . Palmer, and Miller and Storer, all recorded this swallow in the San Benito Mountain region. On 21 June 1936, Palmer collected two breeding males (testes 13 x 9 mm and 12 x 8 mm, respectively) 1 mile south of the summit of Santa Rita Peak. Eight years later, on 9 August 1944, at 1 mile southeast of San Benito Peak, Miller and Storer noted that individuals of this species were “overhead frequently.” In contrast, we did not record Purple Martins. Therefore, we conclude that the species no longer occurs as a summer resident. Davis et al. (1980) state that the Purple Martin was last recorded at the Hastings Reservation in Monterey Co. on 30 June 1958. Moreover, Arbib (1979) reports the general decline of this species throughout its range in recent years. VIOLET-GREEN SWALLOW (Tachycineta thalassina). This species was fairly numerous on San Benito Mountain in 1983 and 1984. Ten individuals were seen foraging over the forest and near the roads on 8-9 June 1983, and, similarly, several swallows were recorded daily during our work in May 1984; on 17 May, we counted eight individuals along our 3- mile transect. These birds commonly foraged in flocks, often over deep, bare serpentine canyons surrounded by forest near San Benito Peak. Although some of these birds may have been migrants, a few definite pairs were noted. In addition, we found three suspected nests along the road. One was in a crack in a serpentine rock outcropping near the headwaters of the East Fork of San Carlos Creek, 4500 ft (1373 m) , and two were in earth banks at 3800 ft (1159 m) and 4500 ft; requisite perches consisting of dead -topped trees or exposed tree roots were always present nearby. A breeding female (ova enlarged to 1 mm) was taken on 14 May 1984 near the first nest, and pairs were seen entering and leaving the other two nest openings. Surprisingly, Palmer did not record the Violet-green Swallow on San Figure 3. Habitat of a singing male Gray Flycatcher, San Benito Mountain, 8 June 1983 (see species account). Photo by Carla Cicero 7 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN Benito Mountain in 1936; however, he reported small numbers in late June near a creek at 2 miles north- northwest of New Idria, a mining camp located downslope. Miller noted three individuals over Sawmill Creek on 8 August 1944, but these could easily have been migrants. The records indicate a substantial increase in the breeding population of this species in the region within recent decades. STELLER’S JAY (Cyanocitta stelleri). Palmer failed to observe this species in 1936 and it is uncertain whether the Steller’s Jay bred on San Benito Mountain at that time. Miller, on the other hand, mentioned (MS) two Steller’s Jays calling from a deep, oak- filled canyon on 11 August 1944. He stated that this gulch provided the most favorable habitat for the species in the region, largely because of the lack of “requisite shade” in the open coniferous forest on nearby slopes. Grinnell and Miller (1944:286) also described the need for “cool, wooded canyons or shaded slopes” by interior populations of the Steller’s Jay. We found the species to be common during our recent field work. In 1983, two individuals were recorded on 8 June in dense yellow pines and Incense -cedars near the summit of San Benito Peak. Steller’s Jays were especially numerous in 1984, when individuals were seen daily in the conifers. A male in breeding condition (testis 9x6 mm) was taken along the East Fork of San Carlos Creek, 4200 ft, in a canyon similar to the one which Miller described. We conclude that this jay has increased in abundance on the mountain since 1936. PLAIN TITMOUSE ( Parus inornatus ). As expected, all surveys have listed the Plain Titmouse for the San Benito Mountain region. In 1936, Palmer (MS) found the species to be “common in the blue oaks,” and Grinnell and Miller (1944:308) also reported records for San Benito Mountain, 4400 ft. Grinnell and Miller described the characteristic habitat of the subspecies P. i. inornatus as “open-type woodland of which oaks . . . are exclusive or dominant constituents.” While such a description seems accurate for much of the range in central California, it conflicts with our obser- vations in 1983 and 1984 for San Benito Mountain. There, all species of arboreal oaks are rare or lacking altogether, especially above 3900 ft (1200 m) (Griffin 1975:20). We saw the species commonly in pines, especially P. coulteri and P. sabiniana, with lesser use of P. jeffreyi. Palmer (MS) also reported titmice in conifers. Of interest here is the possible extent to which the Plain Titmouse is occupying coniferous habitat potentially acceptable to the Mountain Chickadee ( Parus gambeli), a species not yet known from San Benito Mountain. The closest breeding locality for the Mountain Chickadee is in the Santa Lucia Range, Monterey Co., at 3000 ft (915 m) (Grinnell and Miller 1944:300-302). PYGMY NUTHATCH ( Sitta pygmaea ), Neither Palmer nor Miller and Storer en- countered this species in 1936 and 1944, respectively. In contrast, we found a substantial population of Pygmy Nuthatches in the area. Several birds were present in the pines near our camp on 13 May 1983, and on 8-9 June 1983 we found a number of individuals in the conifers on the east-northeast slope; one pair was seen at a possi- ble nest cavity in a pine snag. Johnson collected a breeding male (testis 5x3 mm) of the subspecies S. p. pygmaea in an Incense-cedar at approximately x /2 mile east of the summit. In May 1984, the species was again encountered fairly commonly; five birds were counted during one morning in the conifers along San Carlos Creek. The discovery of this form on San Benito Mountain represents a definite extension of known range. The nearest previously -known localities for the species, as listed by Norris (1958:121), are 50 miles to the west of San Benito Mountain at Big Pines, 3700 ft (1130 m) (9 miles [15 km] west of Jamesburg), and at l x /4 miles (2 km) south of Chalk Peak, 3000 ft (915 m), both in Monterey Co. AMERICAN DIPPER ( Cinclus mexicanus) . Although San Benito Mountain has a drier climate than any of the Santa Lucia Range peaks to the west, it has more permanently flowing streams than the latter region (Griffin 1975:7) and, therefore, more potential 8 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN habitat for American Dippers. Nonetheless, the species has never been found in the region. Both San Carlos Creek and Sawmill Creek appeared suitable for this species during our visit in 1983, a year of extra- heavy precipitation and runoff. In 1984, on the other hand, the water flow seemed inadequate. Perhaps annual variation in stream volume is too great to permit colonization. Another factor might also exclude American Dippers from San Benito Mountain. Degradation of water quality by naturally -occurring toxic chemicals could adversely affect aquatic insects upon which dippers forage. Signs in the area currently warn humans that the water is not potable because of chemical contamination. Two biologically-poisonous chemicals, mercury and chromium, have been mined in the region, and an open -pit mine for asbestos is presently active below nearby Santa Rita Peak. Furthermore, the soils derived from serpentine have a serious magnesium- calcium imbalance and are extremely low in total nitrogen and total phosphorus (Grif- fin 1974:12). Such deficiencies would presumably affect the plants upon which some aquatic insects feed. Although Sawmill and San Carlos creeks contain at least small populations of some aquatic insects, as well as a few frogs, the aquatic resources in general may be insufficient to support breeding dippers. BLUE-GRAY GNATCATCHER ( Polioptila caerulea) . Palmer in 1936 and Miller and Storer in 1944 all recorded this species as being the most common bird in the San Benito Mountain region. Furthermore, Palmer collected two males in breeding condi- tion (11 June, testis 6x4 mm; 18 June, testis 6x3 mm) during his trip. In contrast, not a single individual was found in 1983 and only two widely-separated pairs were seen in May 1984, although we spent many hours in the same places and habitats where the previous workers had encountered the species abundantly. Thus, we con- clude that the Blue-gray Gnatcatcher has dramatically declined on San Benito Moun- tain, at least at higher elevations where it previously occurred in large numbers. AMERICAN ROBIN ( Turdus migratorius) . In early June 1983, several American Robins were singing in the yellow pines near moist places along San Carlos and Sawmill creeks. These records are the first for the species from San Benito Mountain. We again recorded several robins in comparable habitats in May-June 1984. Two of these were lone males, one of which was singing vigorously near Sawmill Creek on 12-14 May. The other birds were an interacting pair that responded to imitated Northern Pygmy-Owl (Glaucidium gnoma) calls near San Carlos Creek; the male sang continuously for approximately 30 minutes while the female uttered alarm notes, and then the pair departed together. Although there is still no conclusive evidence that the species nests in the area, the records suggest that a few individuals were at least at- tempting to colonize the mountain. Other nesting localities in central California are scattered through the Coast Range, the nearest being that for Hastings Reservation, Monterey Co Even there it has only recently become established (Davis et al. 1980). San Benito Mountain’s arid coniferous forest provides very limited potential nesting habitat for the species. SOLITARY VIREO (Vireo solitarius cassinii). This species breeds very locally in the San Benito Mountain region, mainly in the deep ravine of the East Fork of San Carlos Creek between 4000 and 4200 ft elevation. There, two pairs and a single male were stationed in May 1984. All three males sang steadily from fixed positions in the can- yon; they were not moving through as is typical of singing migrants of this species. The birds were excited by our presence and decoyed readily to imitated Northern Pygmy- Owl calls; presumably, they had active nests in the dense woodland of Canyon Live Oaks along the stream. We collected two of these males, both in breeding condition (testis 5x3 mm, slight fat; 7x5 mm, slight fat) , on 15 May 1984. On 1 June 1984, another male was singing in mixed Canyon Live Oaks and Coulter Pines at 4300 ft, on the canyon slope high above the East Fork of San Carlos Creek. The generally open and arid coniferous forest surrounding San Benito Mountain is apparently un- 9 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN suitable for nesting Solitary Vireos, although we recorded a singing migrant in such habitat along Sawmill Creek, 4300 ft, on 12 May 1983. Miller collected an immature Solitary Vireo of unknown sex (no fat) in a Digger Pine on 8 August 1944. Palmer does not mention the species. HUTTON’S VIREO ( Vireo huttoni). On 9 June 1983, we saw a singing Hutton’s Vireo in an Incense-cedar near the summit of San Benito Mountain. A second bird may have been present nearby. Several individuals were again recorded in 1984 along the East Fork of San Carlos Creek. Males were singing steadily from Canyon Live Oaks, and an actively -breeding mated pair (male, testis 3x2 mm; female laying, ovary with 4 collapsed follicles, egg in oviduct ready for shell, active incubation patch) was collected on 14 May from a 20 ft oak at the headwaters of the creek, 4500 ft (1373 m) . These are the first records of the species from the region. Palmer, and Miller and Storer, failed to encounter the species several decades ago. This vireo is a com- mon resident in the luxuriant oak woodland at the Hastings Reservation, Monterey Co. Although scarce and local, the Hutton’s Vireo has seemingly colonized the San Benito Mountain area within the past 40-50 years. The limited occurrence of arboreal oaks provides habitat for only a small population. NASHVILLE WARBLER (Vermivora ruficapilla) . According to Grinnell and Miller (1944), this warbler requires open oak or yellow pine forest for foraging and singing, and an understory of scattered shrubs to conceal and shade the nest. These authors state (1944:396) that “the combination is essential and as a consequence this warbler is usually only found in moderately open forests which permit suitable bush growth.” The San Benito Mountain region locally provides these requisite habitat elements and supports a small breeding population of Nashville Warblers, as the following records document. We found four vigorously singing males in mid-May 1984. Two of these males, one of which was identified by a peculiar inflection at the end of its song, were still present on their respective territories on 1 June. These birds were patrolling ter- ritories in pine-brush or oak/pine-brush habitats, and one was seen chasing another warbler. A singing male in reproductive condition (testis 5x3 mm, medium cloacal protuberance, no fat) was taken from a yellow pine on 15 May at the East Fork of San Carlos Creek, 4200 ft; another individual, also in reproductive condition (testes strongly dissimilar in size: left testis 9 x 6.5 mm, right testis 1 x 0.5 mm; large cloacal protuberance, no fat) , was taken on 1 June at the same locality. Our records represent the first for the San Benito Mountain region. The nearest known probable breeding localities for this species occur to the north in the Inner Coast Range of Lake Co. (vicinity of Crockett Peak, N.K. Johnson MS), and to the south in the vicinity of Pine Mountain, Ventura Co. (Garrett and Dunn 1981). To the east, this warbler breeds commonly on the west slope of the Sierra Nevada. YELLOW-RUMPED WARBLER ( Dendroica coronata ) . Palmer failed to record this warbler in 1936. However, Miller (MS) collected a male (testis 1 mm, no fat) in a yellow pine 1 mile southeast of the summit, at approximately 4400 ft, on 10 August 1944. In examining the specimen, he noted that “judging from its condition of molt it may be a local summer resident.” Records obtained in 1984 strengthen Miller’s suspi- cion. On 17 May, a singing male in breeding condition (testis 8x6 mm, very large cloacal protuberance) was taken near San Carlos Creek at 4200 ft (1281 m); a female was seen near this site later that morning. While these individuals could have been late migrants, the evidence suggests that Yellow-rumped Warblers possibly breed in the region. The habitat of open yellow pine appears to be at least marginally suitable for a small summer resident population. Nesting records of the species exist for Monterey Co. in the “yellow pine belt at the summit of coastal slopes” (Grinnell and Miller 1944:403), and Davis et al. (1980) also note that the “Audubon’s Warbler nests within 3 km of the [Hastings] Reservation.” 10 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN BLACK-THROATED GRAY WARBLER (Dendroica nigrescens) . This warbler breeds in a variety of habitats from oak woodland and open coniferous forest to pinyon- juniper woodland. Mixed chaparral is often a common component of the habitat. Warm and at least moderately arid conditions seem essential wherever the species oc- curs (Grinnell and Miller 1944:404-405). Thus, on San Benito Mountain, the open yellow pine forest and/or mixed yellow pine -Canyon Live Oak association, with an understory of manzanita, scrub oak and other species of brush, appears ideal. In June 1936, Palmer recorded (MS) Black- throated Gray Warblers as “common in the con- ifers.” He collected a male (testis 6x4 mm) on 12 June at 1 mile southeast of the sum- mit, 4400 ft. D.H. Johnson took a male at the same place on 20 June. This species was again encountered fairly regularly in August 1944, when Storer reported (MS) scattered families and a few single birds. Miller collected an immature female on 7 August near the summit of San Benito Mountain, 5000 ft. Fifty years later, the Black- throated Gray Warbler is still present on the mountain but in reduced numbers. A sing- ing male was found on 9 June 1983 in a yellow pine at 4800 ft, and several other in- dividuals were recorded in May- June 1984. On 13 May, a silent bird was seen in the brush below San Benito Peak, and another was present on 15 May in mixed yellow pine -Canyon Live Oak- chaparral on the canyon slope above the East Fork of San Carlos Creek, 4500 ft. A third individual was seen on 1 June in a yellow pine near the upper East Fork, 4200 ft. Some or all of these birds, except for the singing individual, were doubtless spring migrants. Although the species still breeds in the San Benito Mountain region, the records indicate a substantial decline in the nesting population between 1936 and 1983-84. WESTERN TANAGER ( Piranga ludoviciana) . Miller and Storer first recorded the Western Tanager on San Benito Mountain, although the species nests on Santa Lucia Peak, Monterey Co. (Grinnell and Miller 1944:440). On 11 August 1944, they noted (MS) one calling at 1 mile southeast of the summit, 4400 ft. Apparently the species was scarce then and, in light of the late summer date and the lack of specimens, it may not have been breeding. In contrast, in May and June 1983- 1984, a large population of Western Tanagers was established for breeding on San Benito Mountain. Five to ten individuals were recorded on a single day, including nine birds during our 3- mile transect. Most of these tanagers were vigorously singing males, but several pairs were observed and a female was seen carrying nest material on 16 May 1984 near San Carlos Creek. A breeding male (testis 12 x 8.5 mm, enlarged cloacal protuberance, no fat) was taken from a yellow pine near the East Fork of San Carlos Creek, 4300 ft, on 15 May 1984. This species has increased dramatically on San Benito Mountain in re- cent decades and we strongly suspect that colonization of the region took place since Palmer’s work in 1936. BLACK-CHINNED SPARROW (Spizella atrogularis caurina) . This subspecies of the Black- chinned Sparrow breeds at only a few localities in west-central California and was considered “rare” by Grinnell and Miller (1944:518). Evidently, the metropolis of the form S. a. caurina occurs on San Benito Mountain. S. a. caurina was first en- countered in the region by Palmer in mid- June 1936, when he recorded seeing 10 or more individuals in the mixed chaparral between 4400 ft and the summit (5241 ft) . He also noted the species from 1 mile south of Santa Rita Peak, 4500 ft (1373 m) . During the same 2 -week period, Palmer collected three adult males (left testis lengths 6 x 3 to 7x4 mm), one juvenile male, and one female (ova enlarged), all from San Benito Mountain, Palmer’s records were reported in Grinnell and Miller (1944:518). Miller failed to record the species in August 1944. However, because Black-chinned Spar- rows are most easily detected by the singing of males, it is probable that he overlooked this species due to the timing of his visit in late summer. In 1983 and 1984, we found males singing fairly commonly in the chaparral at the same localities as Palmer’s obser- vations. Thus, it appears that the Black-chinned Sparrow has maintained a substantial 11 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN breeding population in the region for at least the past 50 years. In view of the very local distribution of S. a. caurina, we are pleased to report the good health of the San Benito Mountain population. Unfortunately, the increasing degradation of brushlands in the region by extensive mining, especially near Santa Rita Peak, and by trailbikes and other off-road vehicles, poses a distinct threat to this isolated population. SAGE SPARROW (Amphispiza belli). Palmer in 1936, and Miller and Storer in 1944, collected a series of specimens of this species high on San Benito Mountain. Miller identified these as intergrades between A. b. canescens and A. b. belli (Grinnell and Miller 1944:501). Because the skins were determined to be intermediates, we were originally prompted to visit this region to inspect the habitat where the sparrows were found. Typical populations of canescens and belli differ strikingly in this regard; canescens prefers shadscale scrub and belli occupies chaparral primarily comprised of Chamise (Adenostoma fasciculatum) . Surprisingly, although we searched for several days in the exact places where the earlier workers found the species very commonly, none could be found. Although San Benito Mountain is cited as a breeding locality for the species, we doubt that they have ever nested there. The four specimens taken by Palmer, and the series of skins taken by Miller and Storer, were all in non-breeding condition, based on examination of gonads. This is understandable for the August series taken by the latter workers, but it is surprising that none of Palmer’s June birds showed breeding activity. Perhaps San Benito Mountain is not a breeding area but rather is a site where post- breeding groups congregate after nesting at lower eleva- tions, either in shadscale scrub in the San Joaquin Valley to the east or in Adenostoma chaparral in the southern Diablo Range. Miller also mentioned (MS) that the Sage Sparrows he found on San Benito Mountain occurred in large flocks, a point which further suggests possible post-breeding movement into the area. Therefore, we may have failed to record the species because our visits were prior to this postulated uphill movement by post- breeders. DARK-EYED JUNCO (Junco hyemalis pinosus). As Grinnell and Miller (1944:510-511) described, juncos of the subspecies J. h. pinosus are distributed inter- ruptedly in west- central California, with the population on San Benito Mountain being especially isolated. All ornithologists who have visited the region, starting with Palmer in 1936, have reported the species. Palmer (MS) found them “In flocks for the most part, 10-15 in number [and] usually in heaviest stands of conifers or very brushy gulches with streams.” He collected an adult male in breeding condition (testis 8x5 mm) on 9 June and juveniles on 12 and 18 June. Miller (MS) took two adult females on 6 and 8 August 1944, and also reported flocks as well as adults with nearly in- dependent young. Storer (MS) collected an adult male (testis 1 mm) on 8 August and stated that the species was fairly common and most numerous near streams. In 1983 and 1984, Dark- eyed Juncos were common; 11 were found along the transect of 17 May 1984. A male taken on 13 May 1984 was breeding (testis 7x5 mm, large cloacal protuberance). No change in historical status is indicated. PURPLE FINCH ( Carpodacus purpureus). The Purple Finch was one of the most abundant species on San Benito Mountain in 1983 and 1984. In a single day we recorded five to ten vigorously singing males and up to 21 individuals along the 3- mile transect. Most of these finches were in mated pairs, and a female was seen carrying nest material on 16 May 1984 near San Carlos Creek at 4200 ft (1281 m). A small series of specimens, all of which were at the peak of reproductive condition, was taken between 13 May and 17 May 1984. The finches preferred clumps of conifers scattered through mixed chaparral, the latter including several berry- producing shrubs that pro- bably were an attractive food source. Unexpectedly, Palmer did not list the species in 1936. Miller stated in 1944 (MS) that Purple Finches were “heard all day at camp,” and he took an immature female at 4400 ft on 10 August. Because Miller’s records were from late summer, they provide no certain evidence for breeding status. These 12 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN data strongly point to a substantial increase in the breeding population of this species since 1936. Indeed, this finch may have colonized San Benito Mountain sometime between 1936 and 1944. This locality defines the eastern edge of the nesting distribu- tion of Purple Finches in the Inner Coast Range of south -central California. CASSIN’S FINCH ( Carpodacus cassinii). On 13 May 1984 we collected a steadily singing male (testis 9x7 mm) in a yellow pine along Sawmill Creek, 1 mile southeast of San Benito Mountain, 4400 ft. Several other probable Cassin’s Finches were subse- quently seen along San Carlos Creek on 16 May in mixed forest of yellow pine and Incense-cedar with an understory of manzanita-scrub oak. Although this finch pro- bably nests in the area, additional evidence is needed. Summer residence has also recently been suggested for Chews Ridge in Monterey Co. (DeSante and LeValley 1971) . Neither Palmer in 1936 nor Miller and Storer in 1944 reported this finch for the San Benito Mountain region. HOUSE FINCH ( Carpodacus mexicanus) . Although less numerous in 1983 and 1984 than its sibling species, the Purple Finch, the House Finch used pine and brushland habitat on San Benito Mountain apparently identical to that occupied by C. pur- pureus. Both species occurred side by side; males of either sang persistently from con- ifer tops and intraspecific chases were noted through the foliage in space occupied by the other congener. Mated pairs were also commonly observed in these areas. In view of such local sympatry of the two species in the same habitat during the nesting season, San Benito Mountain would be an ideal place to study their interactions. A small series of specimens was taken during our visit between 14 May and 17 May 1984, all of which were in reproductive condition. Palmer in 1936 and Miller and Storer in 1944 also recorded the House Finch. LESSER GOLDFINCH (Carduelis psaltria). This species, a common resident of the Inner Coast Ranges of California (Grinnell and Miller 1944:461-462), has definitely increased in abundance on San Benito Mountain within the past half-century. Palmer recorded only four or five individuals and collected a breeding female (ovum 5x4 mm) during his 2- week stay on the mountain in 1936. Similarly, Miller and Storer found the species in 1944 but not in unusual numbers. In contrast, the Lesser Goldfinch seemed to be among the most abundant species in the region in 1983 and 1984. During our June 1983 visit we found at least 40 individuals in the pines and shrubs; these were actively chasing in small groups or in pairs. On 9 June, we col- lected a female in breeding condition (ovum 8 mm). Pairs and singing males were again commonly encountered in May 1984, and on 16 May a male was taken (testis 6 x 6 mm, large cloacal protuberance) near San Carlos Creek, 4400 ft. The reason for this impressive increase in numbers is unknown, although the open forest and brushland seem ideal for the species according to the habitat description of Grinnell and Miller (1944:412). LAWRENCE’S GOLDFINCH ( Carduelis lawrencei ) . This species was also very com- mon on San Benito Mountain in 1983, although it was not as abundant as its con- gener. On 8-9 June, we observed at least 25 birds in the pine and chaparral habitat, many of which were in interacting pairs or in social groups mixed with Lesser Gold- finches. We also saw several pairs during our trips in May of 1983 and 1984. On 16 May 1984, a breeding male was taken (testis 6x4 mm, cloacal protuberance) along San Carlos Creek, 4400 ft. Such numbers represent a substantial increase in the population within the past 40-50 years. Paimer failed to observe any Lawrence’s Goldfinches in the region in 1936. Miller and Storer (MS) did report the species in 1944, but without commenting on numbers present. 13 AV1FAUNAL CHANGE ON SAN BENITO MOUNTAIN DISCUSSION AND CONCLUSIONS Species richness and avifauna! resemblance. In Table 1 we compare the total number of boreal breeding bird species recorded from San Benito Mountain (14) with those from two other areas of west- central California, Monterey (33 species; Miller 1951 plus Dusky Flycatcher [Chandik and Baldridge 1969, DeSante and LeValley 1971]) and the Hastings Natural History Reservation (19 species; Davis et al. 1980). We included Hastings because it is roughly comparable in size to the San Benito Mountain region (Figure 1). Furthermore, the boreal avifauna of Hastings essentially represents a subset of that found in the adjacent Monterey District as defined by Miller (1951). Fourteen species known from Miller’s Monterey component have not been recorded as summer resident at Hastings. However, a number of these species breed in the Santa Lucia Mountains only a few miles from the Reservation. Evidently, these forms require high elevations and cool- adapted forest not found at the Reserve. Such species include the Flam- mulated Owl, Dusky Flycatcher, Mountain Chickadee, Hermit Thrush, Yellow-rumped Warbler, Western Tanager and Pine Siskin. Other species that are missing from Hastings but found in the broader Monterey region need either (a) large permanent streams or rivers (Common Merganser) , (b) heavy woodland or forest in steep-sided canyons (Spotted Owl), (c) the generally moist summer environments and associated thickets found at or near the coast (Winter Wren, Swainson’s Thrush, Wilson’s Warbler and White-crowned Sparrow), or (d) extensive yellow pine forest (Pygmy Nuthatch) . The avifauna of San Benito Mountain is substantially depleted relative to those occurring in the more moist and heavily- wooded Hastings and Monterey areas. This is largely in keeping with its isolation near the western border of the arid San Joaquin Valley. Among the species lacking from the mountain are the Sharp-shinned Hawk, Chestnut- backed Chickadee, Brown Creeper and MacGillivray’s Warbler. All of these nest in both coastal locations but apparently do not breed at San Benito Mountain because of the comparatively stunted and highly insolated conifers there. Another species, the American Dipper, may be excluded from the region because of excessive annual fluctuations in streamflow volume and possible chemical contamina- tion of the aquatic habitat. San Benito Mountain also seems to be missing two species of small forest- woodland owls, the Northern Pygmy- Owl and Flam- mulated Owl. We recorded only the Western Screech-Owl (Otus kennicottii) and Northern Saw- whet Owl during several nights of persistent hunting by means of imitated calls. More intensive searching of the conifers would likely reveal the Northern Pygmy-Owl; Johnson has recorded this species in similarly inferior conifer stands at several localities in the western United States. Otus flammeolus, on the other hand, may not occur, especially in view of the current scarcity of mature conifers in the logged and burned forest. In comparing the boreal avifaunas of the three regions, it was further noted that some species inhabit San Benito Mountain but are absent from either the Monterey District and/or the Hastings Reservation. Of these, the Nashville Warbler is the only species that breeds on San Benito Mountain but not in the other two areas; the Dusky Flycatcher, Pygmy Nuthatch and Western Tanager are shared with Monterey but do not nest at Hastings. 14 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN Table 1. Probable breeding species of boreal birds." HASTINGS SAN BENITO MONTEREY* RESERVATION' MTN. 1. Common Merganser ( Mergus merganser) 2. Sharp-shinned Hawk ( Accipiter striatus) X 3. Mountain Quail (Oreortyx pictus) X [X]‘ 4. Flammulated Owl (Otus flammeolus) 5. Northern Pygmy-Owl {Glaucidium gnoma) X 6. Spotted Owl ( Strix occidentalis ) 7. Northern Saw-whet Owl ( Aegolius acadicus) X X 8. Hairy Woodpecker ( Picoides uillosus) X X 9. Olive-sided Flycatcher ( Contopus borealis) X X 10. Western Wood-Pewee ( Contopus sordid ulus) X X 11. Dusky Flycatcher ( Empidonax oberholseri) X 12. Western Flycatcher ( Empidonax difficilis ) X X 13. Violet-green Swallow ( Tachycineta thalassina) X X 14. Steller’s Jay (Cyanocitta stelleri } X X 15. Mountain Chickadee ( Parus gambeli) 16. Chestnut-backed Chickadee ( Parus rufescens ) X 17. Pygmy Nuthatch ( Sitta pygmaea) X 18. Brown Creeper (Certhia americana) X 19. Winter Wren ( Troglodytes troglodytes ) 20. American Dipper ( Cinclus mexicanus) X 21. Swainson’s Thrush ( Catharus ustulatus) 22. Hermit Thrush ( Catharus guttatus) 23. American Robin (Turdus migratorius) X 24. Wrentit ( Chamaea fasciata fasciata) X [X]' 25. Solitary Vireo ( Vireo soiitarius) X X [Nashville Warbler]* X 26. Yellow-rumped Warbler (Dendroica coronata ) 27. MacGillivray’s Warbler (Oporornis tolmiei) X 28. Wilson’s Warbler ( Wilsonia pusilla) 29. Western Tanager ( Piranga ludoviciana) X 30. White-crowned Sparrow (Zonotrichia leucophrys) 31. Dark-eyed Junco (Junco hyemalis ) X X 32. Purple Finch ( Carpodacus purpureus) X X 33. Pine Siskin (Carduelis pinus) TOTAL NO. SPECIES 19 14 Nomenclature follows 6th edition of the AOU Check-list (AOU 1983). From Miller (1951:584-587), except for species 4, 6, 7 and 25, the first 3 of which were recorded subsequently. The Solitary Vireo has long been known to breed in the Monterey region and was apparently overlooked by Miller. From Davis et al. (1980). Based on present study. Introduced, and thus not included in total for number of species; see species account. Non-boreal subspecies occurs. Species not known to breed in Monterey region. 15 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN Finally, we note that several species (American Robin, Yellow-rumped Warbler and Cassin’s Finch) are either attempting to colonize or are possibly established as breeders in small numbers on San Benito Mountain; thus, the nesting avifauna of this region may actually be somewhat richer than we now conclude. A quantitative method for judging avifaunal resemblance among various regions is provided by the calculation of similarity coefficients (Table 2) . We attempted several approaches, each of which incorporates different informa- tion: (1) Jaccard’s (1902 and 1908) Coefficient of Community; (2) Simple Matching Coefficient (Sneath and Sokal 1973); (3) Simpson’s (1943) Index; and (4) Schilder’s (1955) Index. However, only the results obtained with Jaccard’s Coefficient and the Simple Matching Coefficient are presented here. These techniques are compared by Sneath and Sokal (1973:129-133) and by Udvardy (1969:273). Table 2. Similarity coefficients for avifaunas of four areas of California. Upper right triangular matrix, Jaccard’s (1902) Coefficients. 0 Lower left triangular matrix, Simple Matching Coefficients* (Sneath and Sokal 1973). For either of these coefficients, a value of zero indicates complete avifaunal dissimilarity and a value of one indicates total avifaunal resemblance. 1. 2. 3. 4. 1. Monterey — 0.58 0.38 0.47 2. Hastings Reservation 0.79 — 0.43 0.26 3. San Benito Mountain 0.69 0.81 — 0.21 4. Yosemite National Park c 0.47 0.26 0.22 — a + b- c where a is number of species in larger fauna, b is number of species in smaller fauna, and c is number of species in common. Numbers of species shared by each pair of the four areas are as follows: Monterey-Hastings, 19; Monterey-San Benito Mountain, 13; Monterey- Yosemite, 32; Hastings- San Benito Mountain, 10; Hastings-Yosemite, 18; San Benito Mountain- Yosemite, 14. b c _ m ‘Jjm - - m + u where m = a + s and u = b + c. a is number of shared species, b is number of species in first avifauna that are not in second avifauna, c is number of species in se- cond avifauna that are not in first avifauna, and d is number of species missing from both avifaunas, using as a base the complete list of species found in all avifaunas (68 species, that is, the list for Yosemite [67 species] plus the boreal form of Wrentit found at Monterey and Hastings) . c Data from Johnson (1975:564-567), whose species list was developed from Grinnell and Storer (1924). Four additional species can be added to Grinnell and Storer’s list: Mergus merganser and Contopus sordidulus, two species inadvertently omitted by Johnson; and Parus rufescens and Anthus spinoletta, two species that have recently colonized the Yosemite region. 16 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN Each method for estimating avifaunal resemblance has its merits and weaknesses. According to Udvardy, Jaccard’s Coefficient tends to give a biased index where substantial discrepancies exist in the size of the different faunas. In such cases, the proportional role of the shared taxa (c) is much greater in the smaller fauna (b) than in the larger one (a) , and the coefficient does not take this factor into account. To avoid this problem, Udvardy recommends the use of either Simpson’s Index or Schilder’s Index. In our opinion, results obtained from the latter two indices are misleading because they exclude important data. Although Simpson’s Index evaluates the con- tribution of both the number of shared taxa and the absolute size of the smaller fauna, it is of limited utility because it omits consideration of the size of the larger fauna. Similarly, Schilder’s Index excludes data on the number of shared taxa and thus disregards qualitative faunal differences. Furthermore, it does not incorporate information on the absolute size of the smaller fauna into its computation. We regard Jaccard’s Coefficient and the Simple Matching Coefficient as the most realistic measures of avifaunal similarity because they consider all of the information pertinent to such comparisons. Calculation of Jaccard’s Coefficient includes data on the absolute size of each fauna and on its com- position in terms of number of shared species. The Simple Matching Coeffi- cient is even more comprehensive. It incorporates information on shared species (positive matches), unshared species (mis- matches) , and, important- ly, species missing in the two faunas being directly compared (negative matches) but occurring in at least one of the faunas in the entire comparison group. To our analysis of avifaunal resemblance among the three areas of western California, we added Yosemite National Park in the Sierra Nevada. Yosemite supports the greatest number of boreal breeding species in Califor- nia (67; Johnson 1975 and Table 2, footnote c) and therefore provides a broader perspective by which to judge similarity of the other regions. Many of these species are absent from the boreal environments in the western portion of the state. Consequently, Yosemite is the main source of negative matches between pairs of the three other avifaunas. Therefore, because the Simple Matching Coefficient considers negative matches in its computation, it is a more appropriate measure of similarity among avifaunas when Yosemite is included in the comparison. In contrast, Jaccard’s Coefficient is most useful when comparing only the three western regions because it excludes negative matches from its computation. The spatial relationship of resemblance coefficients is schematically il- lustrated in Figure 4. Jaccard’s Coefficients (Figure 4a) clearly show a gradual avifaunal depletion eastward from Monterey, through Hastings, to San Benito Mountain. This trend matches a similar depletion in bird species richness as one progresses from north to south along the California coast (Miller 1951:589). Miller attributes the latter trend to moisture and temperature gradients. Presumably, similar climatic changes inland from the coast account for the relative impoverishment of the small and local boreal avifaunas considered here. Jaccard’s Coefficients also reveal a stronger avi- faunal relation between Monterey and Yosemite than between Monterey and San Benito Mountain. Finally, the low coefficient connecting San Benito 17 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN Mountain and Yosemite underscores the profound break in boreal en- vironments and associated avifaunas across the San Joaquin Valley. Coefficients derived by the Simple Matching (S,J approach are very similar in magnitude to Jaccard’s Coefficients (S y ) for any pairwise com- parison in which Yosemite is involved (Figure 4b). For example, S jm and S, for both Monterey and Hastings versus Yosemite are identical. However, values of S jm are higher and more uniform than those of Sj when comparing any two of the three smaller avifaunas. This difference arises from the disproportionate influence of negative matches (d) between pairs of coastal avifaunas, caused by the missing Yosemite species. The S, m data point to a strong avifaunal resemblance among Monterey, Hastings and San Benito Mountain. In addition, these coefficients again reveal the substantial dissimilarity in avifaunas divided by the San Joaquin Valley. Temporal change. The data strongly suggest that the breeding avifauna of San Benito Mountain has changed markedly since the surveys of the region in 1936 and 1944. This change has involved both the composition of the avi- fauna and the relative abundance of particular species. We recorded eight species that were not previously known as summer residents on the moun- tain: Northern Saw-whet Owl, Dusky Flycatcher, Gray Flycatcher, Pygmy Nuthatch, Solitary Vireo, Hutton’s Vireo, Nashville Warbler and Western Tanager. In addition, seven other species appear to have increased in numbers within the past 50 years: Olive-sided Flycatcher, Western Wood- Pewee, Violet-green Swallow, Steller’s Jay, Purple Finch, Lesser Goldfinch and Lawrence’s Goldfinch. Finally, three species, two of them formerly com- mon or even abundant, have apparently either vanished or become very scarce on San Benito Mountain in recent decades: Purple Martin, Blue -gray Gnatcatcher and Black- throated Gray Warbler. As one examines these changes more closely, a pattern becomes evident. Most of the species that are either new to the mountain (6, or 75%), or are a. Jaccard's Coefficients b. Simple Matching Coefficients Figure 4. Schematic illustration of the spatial relationships of the four boreal avifaunas and of their resemblance as measured by similarity coefficients. 18 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN currently more abundant (5, or 71%), represent boreal forms characteristic of cool, moist environments. Therefore, fully 79% of the present boreal avi- fauna consists of species that have either arrived or increased in numbers in the past half-century. Importantly, no boreal species present in 1936 has diminished in numbers in the ensuing decades. Furthermore, the three species currently attempting to colonize (American Robin, Yellow- rumped Warbler and Cassin’s Finch) are also boreal forms. Only the Northern Saw- whet Owl is suspect; it could have been present but overlooked in 1936. The remaining two new additions, the Hutton’s Vireo and Gray Flycatcher, although not considered to be of boreal derivation, are adapted to cool habitats in either the oak woodlands or in the elevated valleys and highlands of the interior of the western United States, respectively. Another related trend is shown by the three species unexpectedly missing or scarce on San Benito Mountain in 1983. All of these are associated with either warm and/ or arid environments. Thus, these avifaunal losses are directly opposite in kind to the gains we observed in the latest censuses. Furthermore, we stress that the species previously recorded as being most abundant on the mountain, the arid-adapted Blue-gray Gnatcatcher, is now very scarce. In sharp contrast, several cool- adapted species that were formerly absent or un- common, such as the Western Wood-Pewee, Dusky Flycatcher and Purple Finch, were among the most abundant forms in 1983 and 1984! The conclusion is inescapable that we have witnessed a broad adaptive response by the high -elevation avifauna of San Benito Mountain to a per- vasive environmental change occurring within the last 50 years. One plausi- ble explanation is that the habitat has undergone substantial modification over one-half century, either naturally or through human perturbation. Evidence of extensive logging in the region around the turn of the century and before is provided by existing stumps and by early records (Griffin 1974) . Jepson wrote in 1907 (in Griffin 1975:7) that “the trees have been logged clean for the mines, even the 6-inch stuff taken for logging.” Griffin (1975:43) discusses conifer reforestation in October 1910 in the Clear Creek area of San Benito Mountain. He also notes that Pinus jeffreyi was “probably more dominant prior to the heavy logging for mine timbers.” One habitat change that is difficult to assess is the removal of most of the old-growth timber. Griffin (1974) provides evidence that large old Incense-cedars and Jeffrey Pines were once much more common than at present. Virtually all of the San Benito forest is now second -growth. Another factor could have been fire. In 1936, Palmer noted (MS) a large burn at Santa Rita Peak. Similarly, Miller stated (MS) in 1944, in reference to a spur running northeast from San Benito Mountain, that “a fire has swept the southeast slope to the crest.” It is probable that some of these habitat modifications would have altered the environment in ways selectively favorable to particular species of birds. For example, subsequent chaparral regeneration in the burned areas would have encouraged populations of the Blue-gray Gnatcatcher, a species that both Palmer and Miller reported in numbers. Moreover, as the density of brush increased and as young conifers began to invade, the acreage of habitat appropriate for gnatcatchers would have declined while its suitability for species such as Dusky Flycatchers and Purple Finches would have increased. Natural succession and the eventual 19 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN colonization of conifer seedlings on at least some logged or burned sites also would then allow forest- adapted species to invade. Despite the effects of logging and fire evident early in this century, the field notes of Palmer and of Miller and Storer clearly describe the presence of ex- tensive forest and rich brushland habitats suitable for boreal birds in the San Benito Mountain region in the 1930s and 1940s. Consequently, we prefer another explanation for the avifaunal dislocation. Because of the particular combination of species involved in this secular change, the underlying cause may have been a shift in recent decades toward cooler and more moist sum- mer climates. Two other studies are relevant to this explanation. Ten years ago, Johnson and Garrett (1974) published data to document the westward spread of eight interior bird species into southern California, including seven boreal forms and the Gray Flycatcher. These authors attributed the expan- sion to “some complex pattern of change in recent decades of spring and summer average moisture and temperature regimes . . .” (Johnson and Garrett 1974:54). In addition, Johnson (1974) demonstrated that a striking increase in boreal species had occurred between 1939- 1940 and 1971 in the Grapevine Mountains and on Potosi Mountain, southern Nevada. He speculated (Johnson 1974:336) that, “we are witnessing the recovery in re- cent years of Boreal faunas which were reduced in diversity sometime prior to the census of 1940, perhaps by the deleterious environmental effects of the relatively warm-dry period of the 1930s.” The new and parallel findings from San Benito Mountain provide clear evidence to support these earlier suppositions. Former speculation can now be transformed into a working hypothesis. Since the aforementioned papers, a publication has appeared (Diaz and Quayle 1980) that confronts the issue squarely by presenting substantial in- formation on climatic change in the United States from 1895 through 1977. This elaborate analysis reveals three distinctly different periods in terms of temperature: (1) 1895-1920, cooler than average temperatures; (2) 1921-1954, warmer than average temperatures; and (3) 1955-1977, rever- sal to cooler than average temperatures. Importantly, all of the early surveys of the Grapevine Mountains, Potosi Mountain and San Benito Mountain fall within the warm middle period, and all of the later censuses from the same three regions occurred during or after the cool, more recent period. Despite geographical and seasonal variation in the climatic data, the information of- fered by Diaz and Quayle for the far West is fully compatible with the sugges- tion of decreased average spring and summer temperatures since the mid-1950s. The patterns of moisture are generally more complex and difficult to inter- pret. Nonetheless, Diaz and Quayle (1980:259) conclude that “average summer precipitation in the far western United States was greater in the re- cent period compared to the previous one,” and that winter precipitation in- creased in the Northwest. Diaz and Quayle present two other conclusions of relevance to the present study. First, they show that the recent period has been relatively more stable (reduced variance) in average temperature and total precipitation. This sug- gests that the cooling trend that has occurred since 1955 represents an unambiguous environmental shift, one striking enough to have led to a more 20 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN defined avifaunal displacement than might otherwise have been the case. Second, Diaz and Quayle (1980:264) report that “in the recent cooling period, the greatest drop in mean temperature occurred essentially over those areas that reflected the greatest increases during the warm interval.” We regard this finding as especially significant and exciting. In particular, it implies that if the greatest extremes between warm- arid and cool -moist climates were reached in the same region, then the magnitude of secular en- vironmental change necessary to drive the kind of avifaunal response described here would have been perfectly plausible. SUMMARY We review the breeding avifauna of the isolated San Benito Mountain region, southern Diablo Range, San Benito and Fresno counties, California. Field notes and specimens resulting from concentrated field work in 1936 and 1944, and preserved in the Museum of Vertebrate Zoology, allowed assessment of the avifauna as it existed approximately V 2 century ago. These data are compared in detail with new information gathered in May and June of 1983-1984. The boreal avifauna of San Benito Mountain is contrasted with those of Monterey and the Hastings Reservation to the west, and with that of Yosemite National Park to the east. Species richness of the four regions is compared, and avifaunal similarity is measured by Jaccard’s Coef- ficient and the Simple Matching Coefficient. The avifauna of San Benito Mountain is substantially depleted relative to those of Monterey and Hastings, and it contains only 21% of the boreal species known from Yosemite. Most of the species missing from the region require dense forest, moist thickets and/or aquatic habitats, either at low or high elevations. Such habitats on San Benito Mountain are either limited or impoverished, or are lacking altogether. The similarity coefficients illustrate avifaunal depletion from Monterey inland, through Hastings, to San Benito Mountain. In addi- tion, they underscore the strong break in boreal environments and associated avifaunas across the arid San Joaquin Valley. A comparison of the censuses of 1936 and 1944 with those for 1983-1984 reveals that striking avifaunal changes have occurred in the San Benito Mountain region over the interval of approximately V 2 century. Eight species of probable colonists, and several other forms that have increased profoundly in numbers, are nearly all species of boreal derivation. Three other species, two of which were recorded as being common or abundant in 1936 and 1944, have either declined in numbers or vanished from the mountain; these forms are typically associated with warm and arid en- vironments. Although habitat disruption from fire and logging may have influenced the occurrence of some species, we conclude that the major avi- faunal shift is attributed to secular climatic change. The reduced average temperatures and increased winter and summer precipitation recorded in the western United States since 1955 appear to have dramatically improved en- vironments for boreal species. Apparently we are witnessing a widespread and ongoing adaptive response by mountaintop avifaunas to these more favorable conditions. 21 AVIFAUNAL CHANGE ON SAN BENITO MOUNTAIN ACKNOWLEDGMENTS We are greatly indebted to Dennis Medlin who accompanied us during all of the field work and who assisted in many ways. David DeSante and James R. Griffin kindly read the manuscript and offered many useful comments. Michael Green called to our attention a crucial reference. Dr. Jon Earhart provided useful information on chemical contamination of water. Bonnie Resnick typed the manuscript and Gene M. Christman assisted in the preparation of the figures. Funds for field expenses were provided by the Na- tional Science Foundation through Grant D.E.B. 79-20694 to Johnson (the first author) . LITERATURE CITED American Ornithologists’ Union. 1983. Check-list of North American birds, 6th ed. Am. Ornithol. Union, Lawrence, KS. Arbib, R. 1979. The blue list for 1980. Am. Birds 33:830-835. Cardiff, S.W. & J.V. Remsen, Jr. 1981. Breeding avifaunas of the New York Mountains and Kingston Range: islands of conifers in the Mojave Desert of Califor- nia. West. Birds 12:73-86. Chandik, T. & A. Baldridge. 1969. The nesting season. Middle Pacific Coast region. Aud. Field Notes 23:692. Davis, J., W.D. Koenig & P.L. Williams. 1980. Birds of Hastings Reservation, Monterey County, California. West. Birds 11:113-123. DeSante, D. & R. LeValley. 1971. The nesting season. Middle Pacific Coast region. Am. Birds 25:903. Diaz, H.F. & R.G. Quayle. 1980. The climate of the United States since 1895: spatial and temporal changes. Monthly Weather Rev. 108:249-266. Garrett, K. & J. Dunn. 1981. Birds of southern California. Los Angeles Audubon Society, Los Angeles. Griffin, J.R, 1974. A strange forest in San Benito County. Fremontia 2:11-15. Griffin, J.R. 1975. Plants of the highest Santa Lucia and Diablo Range peaks, California. USDA Forest Serv. Res. Pap. PSW-110, 50 pp. Griffin, J.R. & W.B. Critchfield. 1976. The distribution of forest trees in California. USDA Forest Serv. Res. Pap. PSW-82, 118 pp. (Reprinted from 1972 with supplement) . Grinnell, J. & A.H. Miller. 1944. The distribution of the birds of California. Pac. Coast Avif. 27. Grinnell, J. & T.I. Storer. 1924. Animal life in the Yosemite. Univ. Calif. Press, Berkeley. Jaccard, P. 1902. Lois de distribution florale dans la zone alpine. Bull. Soc. Vaudoise Sci. Nat. 38:69-1.30. Jaccard, P, 1908. Nouvelles recherches sur la distribution florale. Bull. Soc. Vaudoise Sci. Nat. 44:223-270. Johnson, N.K. 1963. Biosystematics of sibling species of flycatchers in the Empidonax hammondii-oberholseri-wrightii complex. Univ. Calif. Publ. Zool. 66:79-238. Johnson, N.K. 1966. Bill size and the question of competition in allopatric and sympatric populations of Dusky and Gray flycatchers. Syst. Zool. 15:70-87. Johnson, N.K. 1975. Controls of number of bird species on montane islands in the Great Basin. Evol. 29:545-567. 22 AV1FAUNAL CHANGE ON SAN BENITO MOUNTAIN Johnson, N,K. 1980. Character variation and evolution of sibling species in the Em- pidonax difficilis-flavescens complex (Aves: Tyrannidae). Univ. Calif. Publ. Zool. 112:1-151. Johnson, N.K. & K.L. Garrett. 1974. Interior bird species expand breeding ranges into southern California. West. Birds 5:45-56. Miller, A.H. 1951. An analysis of the distribution of the birds of California. Univ. Calif. Publ. Zool. 50:531-644. Norris, R.A. 1958. Comparative biosystematics and life history of the nuthatches Sitta pygmaea and Sifta pusilla. Univ. Calif. Publ. Zool. 56:119-300. Schilder, F A. 1955. Statistische Methoden in der Biogeographie. Wiss. Z. Martin- Luther-Univ., Halle -Wittenberg 4:711-716. Simpson, G.G. 1943. Mammals and the nature of continents. Am. J. Sci. 24:1-31. Sneath, P.H.A. & R.R. Sokal. 1973. Numerical taxonomy. W.H. Freeman and Co., San Francisco. Udvardy, M.D.F. 1969. Dynamic zoogeography with special reference to land animals. Van Nostrand Reinhold Co., New York. Weathers, W.W. 1983. Birds of southern California’s Deep Canyon. Univ. Calif. Press, Berkeley. Accepted 1 August 1984 Black-chinned Sparrow Sketch by Narca Moore-Craig 23 Northern Hawk-Owl ( Surnia ulula ) at Cantwell, just outside Denali National Park, Alaska, 17 June 1982. This immature was one of three Roger Harris found in a nest on top of a 3-m broken top snag 3 days earlier. On 17 June the three young were on the ground, with an adult in close attendance— see cover photo, Western Birds 15(2), 1984. Photo by Roger D. Harris 24 CHANGES IN DISTRIBUTION OF OWL SPECIES SUBSEQUENT TO HABITAT ALTERATION BY FIRE BRUCE ELLIOTT, California Department of Fish and Game, 2201 Garden Road, Monterey, California 93940 Information on the effects of major habitat change on the distribution of owls is generally lacking. The result may be that marked changes in density or local distribution go unnoticed. I have compiled records and subjective im- pressions from several observers near China Camp Forest Service camp- ground during a period interrupted by a major forest fire. This information is particularly valuable when it pertains to the California Spotted Owl (Strix oc- cidentalis occidentalis ) , a subspecies which is under study by the California Department of Fish and Game and the U.S. Forest Service because of con- cern for its status. China Camp, a U.S. Forest Service campground at the head of Miller Canyon, is 3.4 km south of Chew’s Ridge summit on the Tassajara Hot Springs Road in the Los Padres National Forest, Monterey County, Cali- fornia. This area has enjoyed a reputation among local observers for the variety and abundance of its fauna. Eight species of owls have been recorded here (Table 1). Of great attraction to most observers have been the Spotted Owls, which have been easily studied here due to their prompt response to imitated or taped calls. In contrast, Western Screech-Owls were seldom noted about this location prior to the fire, although they could always be found throughout the year at lower elevations in the riparian, encinal and oak-savannah habitat a few kilometers north of Chew’s Ridge in Carmel Valley. The occurrence of various owl species in the study area may be sum- marized as follows: two or more pairs of Spotted Owls were noted in the vicinity of China Camp each year between June 1972 and July 1979 (Table 2). Definite evidence of local breeding was secured in 1977 prior to the fire, when a family of Spotted Owls (two adults and at least two young-of-the- year) were present. In contrast, I observed only one Western Screech-Owl near China Camp in 1973 and 1974 respectively; two may have been there in 1976 but no screech-owl was noted in the spring of 1977 prior to the fire. Northern Saw-whet Owls with two young-of-the-year were observed there on a June visit in 1977 and Roberson suspected breeding by this species in the same location in 1976 (Don Roberson pers. comm.). In August 1977, the second largest forest fire in California history (the 77,000 HA Marble-Cone fire) effected large scale habitat changes about Chew’s Ridge. The fire burned almost all the understory of the area and ef- fectively denuded most foliage from various live oak species ( Quercus spp.) and Tanoaks ( Lithocarpus densiflora) . The Tanoak stands on north-facing slopes had been noted as a favorite local Spotted Owl habitat. The fire pattern limited crowning in the larger Douglas-firs (Pseudotsuga menziesii ) in the Chew’s Ridge area. Flammulated Owl habitat (as described by Marcot and Hill 1980) apparently was not markedly affected. Flam- mulated Owls have been almost as abundant since the conflagration as they were previously. Western Birds 16:25-28, 1985 25 OWL HABITAT ALTERATION Table 1. Owl species and their status near the China Camp campground, Monterey County, California. Common Barn-Owl Tyto alba Western Screech-Owl Ofus kennicottii Flammulated Owl Otus flammeolus Great Horned Owl Bubo virginianus Northern Pygmy-Owl Glaucidium gnoma Spotted Owl Strix occidentalis Northern Saw-whet Owl Aegotius acadicus Long-eared Owl Asfo otus -vagrant (or very scarce resident) -see text -local summer resident (19 April to August) -resident (at least two pairs) -resident (two singing birds) -probably resident (high count: 2 pairs plus young) -possibly resident (bred in 1977; present also in 1976 and 1981) -one male on territory 21 May 1967 at China Camp; another heard briefly in 1977 Such was not the case with Spotted Owls— during the spring 1978 survey, only Flammulated, Northern Pygmy- and Great Horned owls were recorded. In the 1979 and 1980 breeding seasons, the latter species assemblage was noted, plus one Western Screech-Owl. In spring 1981, Spotted Owls again were detected, but the calls were all from unburned areas of Miller Canyon at lower elevations well below China Camp. One was heard here on 16 and 25 April, and two were heard on 27 June. Certainly, since the fire, the vegeta- tion type offered no semblance of the foliage types postulated to be prime habitat for Spotted Owls (Grinnell and Miller 1974, Small 1974, Gould 1977, Barrows and Barrows 1978, Marcot and Gardetta 1980, Barrows 1981). Also during spring 1981, a marked increase in the total number of Western Screech-Owls in the burn area was observed. Roberson noted five screech- owls near China Camp in April. During three survey nights between 2 May and 22 June, I encountered numerous individual singing screech-owls along a 2-mile survey route centered on China Camp (2 May, 4 birds; 16 June, 5 birds; 22 June, 6-7 birds). Vocalizations indicated fledged young-of-the-year soliciting feeding. Perhaps the most significant factor influencing the apparent increased oc- currence of screech-owls was the copious sprouting from the trunks and limbs of fire-blackened oaks in the spring of 1981, following three better- than-average precipitation years in the Santa Lucia Range. Sprouting oc- curred at middle canopy and crown height for live oaks and from the basal section of the main trunks of Tanoaks. Prior to spring 1981, most of these trees appeared moribund. Marshall (1967) noted in his discussion of the genus Otus in the American Southwest that periodic burning of appropriate habitat for screech-owls seemed to enhance populations. 26 OWL HABITAT ALTERATION Table 2. Number of Spotted Owls and Western Screech-Owls reported near China Camp U.S. Forest Service campground between 1972 and 1981. (Marble-Cone fire occurred in August 1977.) Spotted Owls Western Screech-Owls 1972 4 - 1973 4 1 1974 4 ( + 2?) 1 1975 4 - 1976 4 2 1977 4 ( + 2) - 1978 - - 1979 - 1 1980 - 1 1981 25 April 1 (a)* 25 April 5 2 May 4 16 June 5 27 June 2 (a) * 22 June 6-7 * Reported by Roberson (pers. comm.) (a) Birds calling from lower elevations in Miller Canyon It must be emphasized that the methodology employed to gather the data was not a systematic uniform census, but rather a series of informal surveys by several independent observers employing heterogeneous methods. Also, Roberson’s taped or imitated calls stressed owl species (Spotted, Flarn- mulated, Northern Saw-whet) other than Western Screech-Owls; the latter could conceivably have been present and non-respondent during some or all of these field sessions. Notwithstanding the latter caveat, the evidence still indicates that Spotted Owls abandoned their former habitat, occupied prior to the Marble-Cone fire, and shifted their distribution downslope into unburned areas near the bottom of Miller Canyon. Whether or not Spotted Owls occurred regularly in the latter area prior to the fire is unknown . The data also suggest that the apparent increase in numbers of Western Screech-Owls in 1981 resulted from a significant increase in appropriate habitat. The serai development of an incipient oak canopy provided the ap- propriate niche to accommodate Western Screech-Owls in an area previous- ly inhabited by Spotted Owls. ACKNOWLEDGMENTS I thank the following individuals for sharing their records and recollections of owl data from the study area: Alan Baldridge, Ronald Branson, Bill Clow, Debra Love Shearwater, William Reese, Don Roberson and Dennis Serdehely. Baldridge, Roberson, Jon Winter, Gordon Gould, Rich Stallcup and Cameron Barrows reviewed one or more drafts of the manuscript and 27 OWL HABITAT ALTERATION provided useful comment and discussion. I also thank Mary Elliott and Gail Nolan Presley for assistance in the field. I wish to dedicate this paper to the memory of the late George M, Sutton in thanks for his kind advice on a mat- ter of mutual interest. LITERATURE CITED Barrows, C. & K. Barrows. 1979. Roost characteristics and behavioral thermoregula- tion in the Spotted Owl. West. Birds 9:1-8. Barrows, C. 1981. Roost selection by Spotted Owls: an adaptation to heat stress. Condor 83:302-309. Gould, G., Jr. 1977. Distribution of the Spotted Owl in California. West. Birds 8:131-146. Grinnell, J & A. Miller. 1944. The distribution of the birds of California. Pac. Coast Avif. 27. Marcot, B. & J. Gardetto. 1980. Status of the Spotted Owl in Six Rivers National Forest, California. West. Birds 11:79-87 Marcot, B. & R. Hill. 1980. Flammulated Owls in northwestern California. West. Birds 11:141-149. Marshall, J. 1967. Parallel variation in North and Middle American screech owls. Monogr. West. Found. Vert. Zool. No. 1. Small, A. 1974. The birds of California. Winchester Press, New York. Accepted 26 November 1983 Spotted, Flammulated and Pygmy Owls 28 Sketch by Keith Hansen SEVENTH REPORT OF THE CALIFORNIA BIRD RECORDS COMMITTEE LAURENCE C. BINFORD, 985 Emily Avenue, Rohnert Park, California 94928 This report of the Western Field Ornithologists’ California Bird Records Committee (CBRC) contains 197 records of 78 species, divided as follows: 174 records (of 65 species) accepted; 18 (17) unaccepted, identification questionable; and 5 (5) unaccepted, origin questionable (i.e., possible escapees). A few of the accepted records involve returning birds or the reevaluation of records previously treated by the Committee. These figures represent a rejection rate of only 11.7%, which is similar to the rates in four of the six previous reports and to the overall average of 15.7% . This average is based on 1140 records treated, of which 179 were judged unacceptable (see Table 1). By way of comparison, the British Rarities Committee had an overall rejection rate of 22% during its first 10 years, with the lowest annual rate being 18% during the tenth year (Wallace 1970). State list. Jones et al. (1981) included 541 species on the California state list. They anticipated and included all species added in the Committee’s fifth report (Luther et al. 1983). The sixth report (Binford 1983) noted the addi- tion of Gray-tailed Tattler ( Heteroscelus breuipes) and Least Auklet (Aethia pusilla ) and the deletion of Yellow Wagtail (Motacilla flava) and White Wagtail (M. alba). At its meeting of 18 February 1984, the Committee removed Acadian Flycatcher and Cook’s Petrel; see Cook’s/Mas Atierra Petrel under Accepted Records and Acadian Flycatcher in Unaccepted Records. The present report officially adds four species to the state list: Smew, Kittlitz’s Murrelet, Barred Owl and Black-backed Wagtail. The California state list thus stands at 543 species. Number of records. The number of records submitted over the years (Table 1) shows a fairly steady but not dramatic rise that I believe combines the effects of increases in the numbers of (1) active birders (plus improved awareness as to where and when to find rarities and how to identify them) and (2) people reporting to the Committee, especially subsequent to the first two reports when observers became aware of the Committee and its func- tions. That the number of rarities present in the state also has increased is suggested by DeSante (1983). Note that the great increase from 93 records treated in the second report to 253 in the third is at least partly a result of the 4-year time lag in publication dates and a concerted effort on the part of the Committee to obtain and validate old records. Given these effects, an even more dramatic increase in the number of records reported might have been expected. That such is not the case ap- pears to be a function of changes in the review list. The total number of species has changed little, from 131 in 1972, 105 in 1973, 107 in 1975, 109 in 1979, 110 in 1980, 116 in 1981, and 117 in 1983 to 122 in the present report. The net decrease of only nine species should have little effect on the number of reports. However, the species composition of the list has changed considerably. Forty-nine forms on the 1972 review list are not to be found on the current list. Many of these are birds that are now recorded regularly, such as Hooded Warbler ( Wilsonia citrina ) and Indigo Bunting (Passerina cyanea). Western Birds 16:29-48, 1985 29 CALIFORNIA BIRD RECORDS .s c l- 0 "rts 15 u 0) 3 "o 01 r o a CD fa- c 0) > cu o> NMOOH^^rN cj CD V • — » -4-< CP (0 DC DC -a 01 CD JD 3 10 ”S a .E c 0 8 0 0 u o 'C « o n in to w ® & u CC * 3 a VO CO LO LO VO VO rH H H CSJ rH LO O O 00 i-h i-h i-h lo VO CO 00 Ov co 4-* Cl) u CD JO 3 3 O 00 ON 0) 3 3 cj io a> _c 0) ia i-i c o '■3 cj CD JO E 3 c CD -C H jd 10 H CD DC _'C 8 cn CD .2 -j2 Tl -H •“ A c a ro c O 8 .Si O d Q) CD -2 & 3 CO 0) CD I- co -q <2 c fa- (0 o . „ a CD co fa- oo sa (/) S Zo -«-i ^ 2 g *a a O cn in 3 CD i- C 3 in CO T3 2 3 in 15 c o o E in CD > i0 CD 3 st 3 3 a "O o > Q DC HI CO z < UJ Other Raptors Red-tailed Hawk Sep Oct Nov Dec Jan Feb Mar American Kestrel Sep Oct Nov Dec Jan Feb Figure 2. Mean monthly population of raptors in the San Jacinto Valley, Riverside Co., California. 127 ROADSIDE RAPTOR CENSUS DISCUSSION Although comparative data for other areas in southern California are lack- ing, the mean numbers of raptors observed during two years of study, 1.5/km and 1.4/km, indicate that the San Jacinto Valley and similar sur- rounding areas are of major importance to wintering birds of prey. Most areas outside southern California studied in a similar fashion (Table 2) are characterized by much lower raptor densities. This indication is especially true for Red-tailed Hawks and American Kestrels. Our study indicates that raptor densities in the San Jacinto Valley are from 5 to 17 times higher than those reported for other areas. However, the areas listed in Table 2 differ in species composition, with Rough-legged Hawks, Golden Eagles ( Aquila chrysaetos) and Prairie Falcons being among the most common species. In northern California, density estimates for Red-tailed Hawks and American Kestrels (Wilkinson and Debban 1980) were similar to those in this study in- dicating that these two areas are probably similar in overall raptor densities. The future existence of areas important to wintering raptors in Riverside County is dubious. Since 1950, the human population of the county has more than quadrupled, and almost all development has occurred in the rich agricultural lowlands west of San Jacinto Valley. Currently, development is expanding into the physiognomically similar Moreno Valley to the north of San Jacinto Valley and into Perris Valley to the southwest. Although it is dif- ficult to assess the impact of the eventual loss of habitat in these interior Table 2. Partial results of seven wintering raptor census studies. Individuals/km driven Rough-legged Red-tailed American All Number of Study area Hawk Hawk Kestrel species species California 0.01 0.5 0.7 1.5 14 (San Jacinto) California 0 0.061 0.54 0.54 13 (Sacramento V.) Colorado 1 ’ 0.022 0.011 0.018 0.11 8 (El Paso Co.) Utah' 0.055 0.053 0.068 0.3 14 (Cache Valley) Utah d 0.014 0.002 0.003 0.1 12 (Provo) Idaho' 0.048 0.019 0.085 Michigan 7 0.059 0.085 0.026 0.32 6 “Wilkinson and Debban 1980 & Bauer 1982 “Gessaman 1982 d Woffinden and Murphy 1977 'Craig 1978 Craighead and Craighead 1956 128 ROADSIDE RAPTOR CENSUS valleys upon wintering raptors, it seems likely that their utilization of other probably suboptimal areas will reduce survivorship. We encourage the initia- tion of similar raptor studies in other portions of California which may identify important wintering areas and point out population trends. ACKNOWLEDGMENTS We thank Bruce A. Henderson and John R. Storrer for their assistance in the field and Terry C. Sciarrotta of the Southern California Edison Company, Division of Research and Development, for his valuable support and assistance throughout the study. Carneron W, Barrows, Peter H. Bloom, Charles T. Collins and Tim Manolis reviewed earlier drafts of this report. This research was financially supported by the Southern California Edison Com- pany, Division of Research and Development through purchase order C1801901. LITERATURE CITED Bauer, E.N. 1982. Winter roadside raptor survey in El Paso County, Colorado, 1962-1979. Raptor Res. 16:10-13. Craig, T.H. 1978. A car survey of raptors in southeastern Idaho, 1974-1976. Raptor Res. 12:40-45. Craighead, J.J. & F.C. Craighead. 1956. Hawks, owls and wildlife. Stackpole Co., Harrisburg, PA. Fretwell, S. 1977. Is the Dickcissel a threatened species? Am. Birds 31:923-932. Gessaman, J.A. 1982. A survey of raptors in northern Utah, 1976-1979. Raptor Res. 16:4-10. Koplin, J.R, 1973. Differential habitat use by sexes of American Kestrels wintering in northern California. Raptor Res. 7:39-42. McKernan, R.L. 1983. San Jacinto Lake, Calif. Pp. 773-774 in Heilbrun, L.H. etal., eds. The eighty-third Audubon Christmas Bird Count. Am. Birds 37:369-792. Mills, G.S. 1975. A winter population study of the American Kestrel in central Ohio. Wilson Bull. 87:241-247. Mills, G.S. 1976. American Kestrel sex ratios and habitat separation. Auk 93:740-748. Newton, I. 1979. Population ecology of raptors. Buteo Books, Vermillion, SD. Olendorff, R.R., D.A. Miller & R.N. Lehman. 1981. Suggested practices for raptor protection on power lines. The state of the art in 1981. Raptor Res. Rep, No. 4:1-111. Wilkinson, G.S. & K.R. Debban. 1980. Habitat preferences of wintering diurnal raptors in the Sacramento Valley. West. Birds 11:25-34. Woffinden, N.D. & J.R. Murphy. 1977. A roadside raptor census in the eastern Great Basin — 1973-1974. Raptor Res. 11:62-66. Accepted 1 1 September 1 984 129 Prairie Falcon and Brittlebush Sketch by Narca Moore-Craig 130 WHITE TERNS ON OAHU PRODUCE SIBLINGS FIVE MONTHS APART DOROTHY H. MILES, 2957 Kalakaua Avenue, Apt. 116, Honolulu, Oahu, Hawaii 96815 White Terns (Gyg/s alba ) commonly breed on remote atolls and islands in tropical and subtropical regions, including the Northwestern Hawaiian Islands (NWHI). In 1961 a pair of these seabirds was reported to be breeding at Koko Head on Oahu (Ord 1961), the only main Hawaiian Island where they have been found. Since then the terns have expanded their nesting area some 16 km to the civic center of Honolulu. Harrison et al. (1984) estimated 50-100 pairs in the main Hawaiian Islands. Dorward (1963) found that the White Tern was one of the few species on Ascension Island to have a distinct annual breeding season, laying about January. Individual pairs laid on the same ledge in successive seasons with an interval of close to a year. On Christmas Island in the Central Pacific Ocean Ashmole (1968) found that incubation and chick-rearing took about 5 months and molt about 5.5 to 7 months. Howell (1978) found the incuba- tion period to be 35 days. Pettit et al. (1981) found the White Tern to be one of only two terns with prolonged incubation and to have the longest incuba- tion in relation to its egg mass of any tern. A single egg is laid but no nest is built. Here I present the results of my study of White Tern breeding biology on Oahu. I describe differences occurring in individual breeding pairs; these previously undescribed differences concern the lengths of intervals between breeding which, in turn, affect the number of offspring produced in one year. STUDY AREA AND METHODS The breeding area of the first pair of White Terns to exhibit an unusual breeding pattern (Pair 1 in 1979) became the focal point of a 6-year study. This small nesting area was located in Kapiolani Park on the south shore of the Island of Oahu between Diamond Head crater and the Pacific Ocean. The 45 m x 90 m area contained 13 ironwood ( Casuarina equisetifolia ) trees spaced 3.6 m to 5.4 m apart and surrounding a central open space. In 1982 this nesting area was extended to include a nearby Kiawe ( Prosopis pallida ) tree. A row of high-rise oceanfront condominiums served as a protective bar- rier. This urban park environment had traffic on three sides and other human activity in the area. Several species of introduced land birds and escaped cage birds competed for nesting trees but no other White Terns bred there. The focal area was one of 16 White Tern breeding areas which I monitored in Kapiolani Park (1975-1984). Breeding here was discovered in October 1970 (Berger 1981). The 68 ha park extends about 1 km from Diamond Head to Waikiki parallel to the shoreline. The park has a central athletic field and numerous picnic areas which receive much human use. In addition to the ironwood from Australia, many large, old trees introduced from Asia and Africa offer the White Terns ample choices of nest sites. I recorded 56 nest sites in 14 species of trees. Breeding pairs sought isolation; distances between Western Birds 16:131-141. 1985 131 WHITE TERNS ON OAHU nests were always greater than 10 m. I generally made daily observations for periods ranging from a few minutes’ check to more than 8 hours. Night observations of sleeping perches in the focal area were made to help deter- mine the identity of individuals remaining in the area. Some terns arrived on their perches after dark and left before dawn; therefore, periodic night checks also assured more accurate data on population size. Beginning in May 1981 chicks were banded at about 5 weeks of age with both a numbered anodized aluminum band and a color-coded plastic band. Moynihan (1962), while studying White Terns on Moto Nui Islet off Easter Island, noted that each bird selected a station on which it perched most of the time. Consistent use of one perch by an unbanded bird during a breeding season and in subsequent seasons provided strong evidence of its identity. The terns’ attachment to a particular perch and to their chosen nest sites, along with slight variations in physical appearance as well as differences in behavior and vocalizations, made individual identification possible. The sex of breeding partners was determined during observations of courting and copulation. Howell (1978) noted that in birds marked before the egg-laying stage he could usually tell by subsequent behavior which was male and which female. Chicks that hatched before 1981, including the first four offspring of Pair 1, were not banded. Nevertheless after 6 years of daily observations of this isolated pair and their extended family, I am convinced that I was observing the same individuals. RESULTS Most pairs of White Terns initiated nesting activity in January or February, reared a single chick and were gone by November. However, some pairs (hereafter called short-cycle breeders) laid again after rearing a chick and hatched second or third chicks. These pairs did not leave the area when an- nual breeders left if they were courting again, incubating an egg or rearing a chick. The percentage of short-cycle breeders increased from 20% in 1979 (1 of 5 pairs) to 37% in 1984 (11 of 28 pairs monitored that year). In 1980 the nest limb of a pair of short-cycle breeders was cut off by tree-trimmers and, therefore, lost to my study. By August 1984 12 pairs had produced off- spring on a short breeding cycle in Kapiolani Park. A pair nesting on private property at Diamond Head reared one chick in 1983 and was discovered to be a short-cycle breeder in 1984, bringing the total known on Oahu to 13 pairs. Relationship Between Three Pairs In 1978 Pair 1 established a new breeding area. An infertile egg was laid on 8 June, incubated for 126 days and abandoned on 12 October when the pair left the area. In January 1979 Pair 1 returned to the same nest and reared two chicks 5 months apart. These two 1979 siblings (hereafter called Pair 2) mated and began breeding in February 1981 at ages 18 and 23 months. In 1980 Pair 1 reared two more siblings 5 months apart. The two 1980 siblings (hereafter called Pair 3) began breeding in December 1981 at ages 16 and 21 months. Pair 2 and Pair 3 remained in their natal area and 132 WHITE TERNS ON OAHU also bred at short intervals; they produced nine third-generation chicks during the same period (1981-1984) that their parents (Pair 1) reared seven additional offspring. Intervals Between Egg-Laying for Three Related Pairs Between June 1978 and December 1984 pairs 1, 2 and 3 laid 24 eggs and produced 20 offspring in the focal area. Intervals between egg-laying are shown in Table 1. I found five other short-cycle breeding pairs in five different areas, one in 1980 and four in 1983. Two of these pairs had been recorded as annual breeders because they had reared a single chick during the previous year. In 1984 I discovered that four more pairs of annual breeders had laid at short in- tervals and produced chicks. Therefore, a total of six pairs changed their Table 1. Dates of egg laying, approximate intervals between eggs laid, and number of eggs laid and chicks fledged for three related White Tern pairs in Kapiolani Park, Oahu, Hawaii, from June 1978 to December 1984. Date Interval Date Interval Date Interval TOTAL Year Egg (months) Egg (months) Egg (months) Eggs Chicks PAIR 1 1978 8 Jun 8 1 0 1979 16 Feb 5 11 Jul 7 2 2 1980 24 Feb 4 3 Jul 4 2 2 1981 16 Jan 5 2 Jun 5 28 Oct 5 3 3 1982 27 Mar 10 1 0 1983 11 Jan 5 29 May 7 23 Dec 5 3 3 1984 16 May 7 22 Dec 2 1 Total 14 11 PAIR 2 1981 26 Feb 5 21 Jul 7 2 2 1982 2 Mar 12 1 1 1983 14 Mar 16 1 0 1984 23 Jul 1 1 Total 5 4 PAIR 3 1981 13 Dec 15 1 1982 1 1983 13 Mar 8 8 Nov 5 2 2 1984 31 Mar 5 15 Sep 2 2 Total 5 5 Grand Total 24 20 133 WHITE TERNS ON OAHU breeding pattern from an annual cycle to a short cycle between 1982 and 1984. Two of these pairs hatched second eggs in December 1983 after rearing chicks and reared three offspring each in 1984, and one of these pairs laid again on 24 December 1984. Of these 12 pairs, 6 bred on a short cycle from their first year of breeding (1979-1984). Dorward (1963) recorded the intervals between egg-laying for 59 pairs of White Terns. Most (35 pairs) laid at intervals of 11 or 12 months. Of 15 birds banded in the first season, all but 3 returned with the same partner and laid on the same spot in the second season, 1 recorded intervals of 11 to 15 months between egg-laying for 10 pairs that laid on the same nest site for 2 to 5 years and reared a single chick during each year. This finding is similar to that of Ashmole (1968) and Dorward (1963). Breeding Success I compared the breeding success during 5-year periods of two pairs that bred annually (Pair A and Pair B) with that of a pair that bred on a short cycle (Pair 1). These three pairs had been monitored regularly between 1978 and 1984 and supplied the most reliable data over the longest period. Pair 1 reared more than twice the number of offspring as Pair A or Pair B (Table 2) . Intersibling Behavior Howell (1978) noted that young White Tern chicks were tolerant of any adult bird that came to the nest site; such visitors frequently approached, preened and brooded a small chick. If a parent returned while the visitor was present, it quickly attacked and chased away the intruder. 1 observed similar behavior and also feeding of chicks by visiting adults. In August 1979 a 5-day-old chick was visited by its older sibling, a 5-month-old fledgling identified by black underwing coverts. A parent sitting nearby after brooding the chick did not chase off the older sibling during this first visit, but subsequent visits were not tolerated by either parent. In 1980 this same bird, then a juvenile and still showing black underwing coverts, was often observed guarding, occasionally feeding or awkwardly attempting to brood the new chick (its youngest sibling) when the parents were away, but was always chased off when a parent returned. Howell (1978) found older chicks to be very aggressive toward non-parent adults or juveniles that approached. I found that older chicks— from about 21 days of age to first flight at about 45 days of age — assumed an aggressive posture when a non-parent adult sat near them or attempted to brood them, but not all succeeded in routing the visitor. I also observed an attack on a 46-day-old chick by an adult visitor that was breeding in an adjacent tree. The adult bird grasped the bill of the chick in its bill and twisted it back and forth until the chick fell, resulting in its first flight. I also observed the contrary behavior when a 10-week-old fledgling grasped the bill of an adult visitor that had just fed it a fish and forced the struggling adult off the nest limb. I have found no data in the literature on the White Tern that describes the ages and behavior of offspring at critical stages of development, nor precise figures on the length of time that parents continue to feed them after they fledge. From 1978 to 1984 I monitored the rearing of 95 chicks of 45 pairs 134 WHITE TERNS ON OAHU and found the following in most parents and offspring: both parents fed the offspring on the nest site for the first 45 days, until the chick was 6.5 weeks old and made its first trial flight off the nest limb. The fledgling then picked a perch of its own above the nest if possible. It used its voice for the first time, if needed, to attract a parent with fish to its new location. After 3 weeks of practice flight in the breeding area, the 10-week-old fledgling flew to sea where it practiced fishing for 3 weeks while the parents Table 2. A comparison of the breeding success during 5-year periods of two pairs of White Terns that bred annually (Pairs A and B) and one pair that bred at intervals of 5-7 months (Pair 1) in Kapiolani Park, Oahu, Hawaii. Egg Egg Chick Chick Eggs Chicks Offspring Year laid lost* hatched lost** laid fledged reared PAIR A 1978 May Jun 1 1 1 1979 Apr May 1 1 1 1980 Jan Feb 1 1 1 Dec 1 0 1981 Jan 0 0 0 1982 Apr May Jun 1 1 0 T otals 5 4 3 PAIR B 1979 Aug Sep 1 1 1 1980 Apr May 1 1 1 1981 Mar Apr 1 1 1 1982 Apr May Jun 1 0 0 1983 Mar Apr 1 May Jun 1 1 1 Totals 6 4 4 PAIR 1 1979 Feb Mar Jul Aug 2 2 2 1980 Feb Mar Jul Aug 2 2 2 1981 Jan Feb Jun Jul 3 3 3 Oct Nov 1982 Mar Oct 1 0 0 1983 Jan Feb May Jun 3 3 3 Dec Jan ’84 Totals 11 10 10 Two eggs abandoned due to storm and pigeons; one to egg infertility. Fledgling injured in flight; four-week chick vanished; (causes unknown). 135 WHITE TERNS ON OAHU continued to feed it. At 13 weeks of age it could feed itself but parents con- tinued to hold fish for it, sometimes for many hours. The independent off- spring then picked a new perch or left the area. Offspring were fed for 91 days. Total parental care including incubation required 126 days minimum. DISCUSSION White Terns breeding on a “short cycle” produced twice the number of off- spring each year as annual breeders. As the population in my study area grew the number of pairs that bred at short intervals increased. When some of the annual breeders changed their breeding pattern to short-cycle breeding, they produced twice the number of offspring they had been pro- ducing during their first year or two of breeding. This unexpected finding suggests that a change may be taking place in the breeding biology of the Oahu White Terns that may not be taking place in the White Terns in other areas. At French Frigate Shoals, for example, en- vironmental changes brought about by human occupation have caused a White Tern population to become established where none existed before 1965 (Rauzon & Kenyon 1984). Also, according to Harrison et al. (1984) the White Tern population on Midway Atoll has greatly increased in the past 50 years due to the introduction of the ironwood (Casuarina litorea ) . This tree provided additional habitat which is relatively unaffected by Black Rats (Rattus rattus) introduced in 1943. These environmental changes increased the number of White Terns in these two areas but no change in their annual breeding pattern was noted. The short intervals between breeding found in the Oahu White Terns ap- pears to be unique to Oahu. Other White Tern populations have not been found to exhibit short-cycle breeding; long-term monitoring is needed to con- firm these differences in their breeding biologies. Oahu may have survival advantages not found in other areas: mild climate, unlimited choice of arboreal nest sites, habitats that allow low-density breeding and the privacy White Terns seem to prefer. Nearby fishing grounds provide a variety and year-round availability of food (Harrison et al. 1983). The occasional feeding of chicks by older siblings may minimize the difficulty of rearing two or three offspring during a year. Lack (1968) said, “adaptations of birds to the external environment which affect the number of young raised . . . are closely interrelated and have evolved through natural selection in the natural habitat of the species. Hence findings in habitats much modified by man may be misleading.” A comment by Darwin (1859) regarding inhabitants of oceanic islands may also be food for thought: “Species occasionally arriving after long intervals of time in the new and isolated district, and having to compete with new associates, would be eminently liable to modification, and would often pro- duce groups of modified descendents.” The similarity in the breeding patterns of Pair 1 and four of their offspring strongly suggests a genetic basis for short-cycle breeding in White Terns. However, the apparent behavioral plasticity of some pairs switching from an- nual to short-cycle breeding leaves this question open for further research. 136 WHITE TERNS ON OAHU Figure 1. Two-week-old first chick of Pair 1, 3 April 1979, on nest site in Casuarina tree where previous egg was laid in June 1978. Figure 2. Seventh chick of Pair 1— a day-old ball of fluff— in the small fork of the Casuarina tree where eight eggs were laid previously. The bird on the right is side- stepping away to let her mate take his turn brooding the chick. Photo taken 3 December 1981. 137 WHITE TERNS ON OAHU Figures 3 and 4. Typical postures of a White Tern visitor before it attempts to brood a young chick This chick is 1 week old. An older chick would display a defensive posture — leaning forward with bill open— and resist the approach of any visitor except its parents. Photos taken 9 December 1981. 138 WHITE TERNS ON OAHU Figure 5. This rare photo of Pair 1 parent and two 1979 siblings shows the 5-month-old sibling — identified by black underwing coverts — visiting the new chick on 20 August 1979. It was not chased off as it was in subsequent visits. Photos by Dorothy H. Miles 139 WHITE TERNS ON OAHU ACKNOWLEDGMENTS Barbara Macaulay showed me a young White Tern in a Kiawe tree in July 1975. The parents returned to the same nest site in 1976 and became the first breeding pair in my study. Her report of this pair was published in the Hawaii Audubon Journal (Macaulay 1976). Kim and Teruo Sasaki, Kay Ahearn, Pat Purcell, Venona Honchell and many others to whom I owe my gratitude have reported valuable information to me over the years. I am especially grateful to Barbara B. DeWolfe who first made me aware of the value of my work and urged me to band the birds and publish my findings. Banding, care and replacement of fallen chicks, medical treatment and autopsies were made possible through the cooperative efforts of the Hawaii Division of Forestry and Wildlife, the Honolulu Zoo, the Honolulu Fire Department Unit 7, and the Department of Parks and Recreation, with special thanks to Ron Walker, Tim Burr, Tim Sutterfield, Marie Morin, Peter Luscomb, Margo Lengen, Keo Tenjoma, Bob Miyashita and Steve Salis; and to Drs. Eric Ako and R.W. Steckelberg for veterinary services. I also thank the U.S. Fish and Wildlife Service, the Zoology and Science departments of the University of Hawaii and all who generously supplied information and references including G.C. Whittow, C.J. Ralph, Maura Naughton and Carl Fieber. For their help and advice on the first drafts of this paper I am indebted to Andrew J. Berger, Ronald Walker, Marie Morin and Marion Steinhauser, and for later drafts, Sheila Conant, Craig Harrison and Leonard Freed. LITERATURE CITED Ashmole, N.P. 1968. Breeding and molt in the White Tern (Gygis alba ) on Christmas Island, Pacific Ocean. Condor 70:35-55. Berger, A.J. 1981. Hawaiian birdlife. 2nd ed. Univ. Press Hawaii, Honolulu. Darwin, C.R. 1859. The origin of species. John Murray, London. Dorward, D.F. 1963. The Fairy Tern (Gygis alba ) on Ascension Island. Ibis 103b:365. Harrison, C.S., M.B. Naughton & S.I. Fefer. 1984. The status and conservation of seabirds in the Hawaiian Archipelago and Johnston Atoll, in J.P. Croxall, R.W. Schreiber & P. Evans, eds., Status and conservation of the world’s seabirds. ICBP Tech. Publ. # 2. Harrison, C.S., T.S. Hida & M.P. Seki. 1983. Hawaiian seabird feeding ecology. Wild!. Monogr. 85. Howell, T. 1978. Ecology and reproductive biology in the White or Fairy Tern (Gygis alba). In Ecology and reproductive behavior of the Gray Gull and of the Red- tailed Tropic Bird and the White Tern on Midway Island. Natl. Geogr. Soc. Res. Rep. Vol. 10:274-284. Lack, D. 1968. Ecological adaptations for breeding in birds. Methuen & Co. , London. Macaulay, B. 1976. Field notes. Elepaio 36:139-140. Moynihan, M.H. 1962. Hostile and sexual behavior patterns of South American & Pacific laridae. Behavior (Suppl.) 8. Ord, M.W. 1961. White Terns at Koko Head, Oahu. Elepaio 22:17-18. Pettit, T.N., G.S. Grant, G.C. Whittow, H. Rahn & C.V. Paganelli. 1981. Respiratory and gas exchange and growth of White Tern (Gygis alba) embryos. Condor 83:355-361. Rauzon, M.J. & K.W. Kenyon. 1984. White Tern nest sites in altered habitat. Elepaio 44:79-80. Accepted 17 January 1985 140 WHITE TERNS ON OAHU ADDENDUM This report updates my continuing study to July 1985 and presents new evidence that attacks on chicks by adult or juvenile visitors appear to be pre- copulatory behavior and can limit the number of offspring reared (e.g., Fair 2, Table 1). Twenty-four pairs were monitored. Five new pairs reared three chicks. Nine returned annual breeders reared six chicks, lost one, and were in- cubating one. A pair that lost their chick last year (the attackers of chicks of Pair 1 and Pair 2 since 1982) had not yet laid. Ten pairs of short-cycle breeders had produced 13 chicks by mid- July, including 3 sets of siblings. (Of 12 pairs, 2 had lost their nest limb due to tree-trimming in 1981 and 1984.) The three focal pairs (Table 1) increased their total production from 20 to 24 offspring. The failure of Pair 2 to produce a sibling in 1982 and the loss of their first egg in 1983 and first chick in 1984 can be attributed to hostile attacks by a pair that had usurped their night perch. One of this pair seemed determined to throw their chick off the nest and take over the nest site. I had seen this behavior in unmated juvenile siblings since 1980, but never the take-over of a perch by an intruder. 1 had observed attacks by this pair in 1983 and 1984. From 4 May to 20 May 1985, I watched them daily at- tacking the 3-week old chick of Pair 2, It was finally wrestled to the ground, but rescued. Both parents aggressively chased them, but attacks continued until courting and copulation began, after which a benign visit was made to the chick and they left the area, apparently to find a new nest site. 141 TREASURER’S REPORT WESTERN FIELD ORNITHOLOGISTS, INC. Cash Flow Statement for 1 January 1984 to 31 December 1984 Cash on hand, 1 January 1984 $ 3,499.46 RECEIPTS Membership Boat Trips Annua! Meeting Back Issues Reprints Interest Miscellaneous $13,731.45 4.403.00 1.896.00 512.00 1,209.28 42.08 35.00 21,828.81 DISBURSEMENTS Western Birds Boat Trips Annual Meeting Membership/Business Services Postage Miscellaneous $10,826.66 3,950.00 989.87 1,449.53 1,487.92 176.70 18,880.68 Cash on hand, 31 December 1984 $ 6,447.59 J. Garth Alton. Treasurer 142 NOTES VOCALIZATIONS OF THE BLACK-HEADED GROSBEAK GARY RITCHISON, Department of Biology, Utah State University, Logan, Utah 84322 (present address: Department of Biological Sciences, Eastern Kentucky University, Richmond, Kentucky 40475) Although the breeding biology and singing behavior of the Black-headed Grosbeak (Pheucticus melanocephalus ) have been examined (Weston 1947; Ritchison 1983a, b; 1985), little information is available concerning grosbeak vocalizations. The pur- pose of this note is to describe the vocalizations of the Black-headed Grosbeak and briefly indicate the context(s) in which the vocalizations were uttered. Observations and recordings were made almost daily from 1 April through 31 August in 1977 and 1978 at the Malibu-Guinavah Forest Camp, 10 km east of Logan, Cache County, Utah (see Ritchison 1983a for description of this area). Grosbeak vocalizations were recorded at 9.5 cm/sec with a Nagra I1IB tape recorder equipped with an Altec 633A microphone and a 62-cm parabolic reflector. Vocalizations were analyzed with a Kay Elemetrics Sona-Graph (Model 606 IB) using the wide-band filter. Sound parameters were obtained by converting linear measurements on the sonagrams into time (horizonal axis) or frequency (vertical axis) measurements. The chip call (Figure 1A) consisted of a single note averaging 0.04 ± 0.01 sec (N = 22) in duration. This call began at a frequency of 3.10 ± 0.04 kHz and rose sharply to a frequency of 6.00 ± 0.15 kHz. This call was uttered by both male and female grosbeaks in a variety of situations, i.e., as paired birds moved through their territories prior to nesting or when an adult approached the nest to assume incubating or brooding duties or to bring food to the young (Ritchison 1983a) . The wheet call (Figure IB) averaged 0. 10 ± 0.02 sec (N = 35) in duration. This call exhibited an up-slur, beginning at an average low frequency of 2.20 ± 0.18 kHz and rising to an average high frequency of 2.90 ± 0.13 kHz. This call was given by both males and females and was only uttered when a bird took flight. The squeal call (Figure 1C) consisted of a single note repeated in a series. Individual notes averaged 0.08 ± 0.01 sec (N = 54) in duration and were uttered at a frequency of 3.5 to 4.0 kHz. This call was given by both males and females when being handled or when a nest containing eggs or young was approached by a human or other poten- tial predator. For example, this call was uttered by a female when a Sharp-shinned Hawk (Accipiter striatus) flew to a nest and removed two nestlings. Similar calls have been reported in a number of species (Norris and Stamm 1965, Stefanski and Falls 1972, Rohwer et at. 1976) . Such calls could startle a predator and allow a captured in- dividual to escape or could elicit harassment or distraction behavior that may divert the attention of a predator from a nest or young. The che-le-up call (Figure ID) was given at a frequency of 2.0 - 3.0 kHz and averaged 0.28 ± 0.02 sec (N=18) in duration. This call was given by young grosbeaks from the time they were a day or two old until just after fledging. While giv- ing this call, a young grosbeak would stretch its head and neck upward, flap its wings, and open its mouth, Such behavior elicited feeding from the adults. The phee-oo call (Figure IE) averaged 0.44 ± 0.04 sec (N = 20) in duration and was uttered at a frequency of 2.0 - 3.5 kHz. This call was first given by young Western Birds 16:143-145, 1985 143 NOTES grosbeaks a few days prior to fledging and was uttered by the young for several weeks after fledging. This call was given when a young grosbeak sighted a parent with food or heard a parent calling or singing (Ritchison 1983a,b). The juvenal squeal call (Figure IF) consisted of a single note repeated rapidly in a series. The individual notes averaged 0.15 ± 0.01 sec (N = 44) in duration with an average frequency of 3.0 - 4.0 kHz. This call was uttered in conjunction with phee-oo calls (Ritchison 1983a, b). 1 wish to thank Keith L. Dixon for his guidance throughout this study. I also thank Cameron Barrows and an anonymous reviewer for helpful comments on the manuscript. This investigation was supported by grants from the Frank M. Chapman Memorial Fund of the American Museum of Natural History and from Sigma Xi. B C 00 S^ ^ * p A p T I N X w > 2 a l 0 E A - — Figure 1. Sonagrams of Black-headed Grosbeak vocalizations: (A) chip; (B) wheet: (C) adult squeal: (D) che-le-up; (E) phee-oo; (F) juvenal squeal. 144 NOTES LITERATURE CITED Norris, R.A. & D.D. Stamm. 1965. Relative incidence of distress calls or “squeals” in mist-netted birds. Bird-Banding 36:83-88. Ritchison, G. 1983a. Breeding biology of the Black-headed Grosbeak in northern Utah, West. Birds 14:159-167. Ritchison, G. 1983b. The function of singing in female Black-headed Grosbeaks: family-group maintenance. Auk 100:105-116. Ritchison, G. 1985. Variation in the songs of female Black-headed Grosbeaks. Wilson Bull. 97:47-56. Rohwer, S., S.D, Fretwell & R.C. Tuckfield. 1976. Distress screams as a measure of kinship in birds. Am. Midi. Nat. 96:418-430. Stefanski, R.A. & J.B. Falls. 1972. A study of distress calls of Song, Swamp, and White-throated sparrows. I. Intraspecific responses and functions. Can. J. Zool. 50:1501-1512. Weston, J.G., Jr. 1947. Breeding behavior of the Black-headed Grosbeak. Condor 49:54-73. Accepted 11 February 1985 NOTES UNUSUAL WESTERN BLUEBIRD EGGS DAVID HAYES, 1561 So. Queen St., Lakewood, Colorado 80225 Usually bluebirds ( Sialia spp.) lay unmarked light blue eggs (Bent 1949). Albinistic eggs have been reported for all three North American species (Musselman 1935, Laskey 1939, Power 1966, Eltzroth 1983), but are considered unusual. The fertility of albinistic eggs has been confirmed for the Eastern Bluebird (S. sialis ; Musselman 1935, Laskey 1939) and the Mountain Bluebird (S. currucoides; Power 1966, Munro et al. 1981) but not the Western Bluebird (S. mexicana). During the 1984 nesting season, a Western Bluebird laid 16 white eggs in three separate clutches (6, 5 and 5 eggs) in the same nest box near Golden, Jefferson Co., Colorado. All 16 eggs were fertile and of normal weight (pers. obs.). Their average dimensions were 20.1 x 15.6 mm, which according to Bent (1949) is typical for the Colorado race bairdi. This high fertility rate is similar to that for albinistic eggs of the Mountain Bluebird (96.1%; Munro et al. 1981) and in the Eastern Bluebird (96.1%; Laskey 1939). The second clutch of 5 eggs was destroyed by a House Wren (Troglodytes aedon ) , which I determined using criteria described by Pinkowski (1975) . Fertility was determined by finding the 5 partially developed eggs shortly after they were destroyed. Those clutches that hatched did so within the usual 2- week incuba- tion period (Eltzroth 1983). The nestlings appeared to be typical and grew in a characteristic manner (McCluskey et al, 1977), were banded at about 10 days of age and fledged 19 to 21 days after hatching. The female did not manifest any abnormal coloration. She was captured and banded during the fifth day of incubation of the first clutch and weighed a normal 31.0 g. Both adults cared for the nestlings. I thank Ed and Cindy Betts for allowing access to their property where the birds nested, Robert R. Cohen for assisting in collecting the data and commenting on this manuscript, and Don Elias and Laurence C. Binford for helpful suggestions on the manuscript. LITERATURE CITED Bent, A.C. 1949. Life histories of North American thrushes, kinglets, and their allies. U.S. Natl. Mus. Bull. 196. Eltzroth, E.K. 1983. Breeding biology and mortality of Western Bluebirds near Corvallis, Oregon. Sialia 5:83-87. Laskey, A.R. 1939. A study of nesting Eastern Bluebirds. Bird Banding 10:23-32. McCluskey, D C., J.W. Thomas & E.C. Meslow. 1977. Effects of aerial application of DDT on reproduction in House Wrens and Mountain and Western bluebirds. Pac. Northwest For. & Range Exp. Stn. Portland, OR, USDA For. Serv. Res. Pap. PNW-228. Munro, H.L., D.H. Munro &R.C. Rounds. 1981. Fertility of albinistic eggs of Moun- tain Bluebirds. Auk 98:181-182. Musselman, T.E. 1935. Three years of Eastern Bluebird banding and study. Bird Banding 6:117-125. Pinkowski. B.C. 1975. A summary and key for determining causes of nesting failure in Eastern Bluebirds using nest boxes. Inland Bird Banding News 47:179-186. Power, H.W. , III. 1966. Biology of the Mountain Bluebird in Montana. Condor 68:351-371. Accepted 6 May 1985 146 Western Birds 16:146, 1985 NOTES FIRST UTAH RECORDS OF THAYER S AND MEW GULLS, WITH COMMENTS ON THEIR REGIONAL DISTRIBUTION AND STATUS MICHAEL H. TOVE, Department of Biology, Utah State University, Logan, Utah 84322 Over the last few decades, there has been a generally widespread increase in North American gull populations (e.g., see Conover et al. 1979, Am. Birds regional reports). Although this trend principally involves the commoner species, a number of extralimital species (i.e., “rarities”) also have been documented. However, the ap- parent increase in reported rarities exceeds that of the commoner species. This ap- parent increase is at least partly due to an increase in the number and expertise of field observers (see Fussell et al. 1982). A significant proportion (majority?) of these “rarities” are immature birds, notable in being difficult to identify (Fussell et al. 1982, Grant 1982, Farrand 1983). Recent identification articles (e.g. Gosselin and David 1975, Lehman 1980, Lauro and Spencer 1980) as well as the newer “sophisticated” field guides (e.g. Farrand 1983, Scott 1983) have greatly contributed to heightened observer awareness, resulting in increased discoveries of “rarities.” Thus, it should not be surprising to find that previously unrecorded species “suddenly” occur with regularity in small numbers. However, apparently sudden changes in status and distribution of a given species should be viewed with caution and, for each case, evidence supporting a particular explanation should be provided. On 13 November 1982 I observed two first winter Thayer’s Gulls (Larus thayeri) fly- ing across an impoundment at Farmington Bay, north of Salt Lake City, Utah. Both individuals were paler and more uniformly tan-colored overall than nearby immature Herring (L. argentatus) or California (L. caiifornicus ) gulls. In flight, the back and up- per wings were notably lacking in contrast except for the three outermost primaries and the tips of the next four to six primaries, which were somewhat darker brown. From below, the primaries and secondaries were white. The upper tail surfaces were brown and slightly darker than the outermost primaries. The bills of both birds were entirely black. Both had darker feathers around the eyes, resulting in a “punched-in- the-eye” appearance. All of these characters are consistent with descriptions of typical first winter Thayer’s Gulls (Gosselin and David 1975, Lehman 1980) and collectively satisfy the requirements to “build a case for identification” (see Gosselin and David 1975, Fussell et al. 1982). On 9 February 1984 I located a first winter Mew Gull (L. canus brachyrynchus) at the Salt Lake City sanitary landfill (Figure 1). The bird was in the company of some 4000 gulls, of which roughly two-thirds were Ring-billed (L. delawarensis) , Relative to the Ring-billed Gulls, the Mew Gull was easily 10% smaller and appeared shorter- legged. Its bill was a little shorter and about half the thickness of that of a Ring-billed. The small bill, in conjunction with a rounded crown resulted in a “dove-like” ap- pearance. The body plumage was uniformly grayish-brown except for a slight profu- sion of slate-gray feathers on the upper back, and whitish mottling in the belly. The tail was grayish brown and blended into heavily barred upper tail coverts. The under tail coverts were mottled brown on white, and generally darker than the lower belly. In flight, the upper wing coverts were darker brown and primaries lighter colored than those of immature Ring-billed Gulls. A careful study of the middle secondary coverts and tertials revealed distinctly rounded and evenly colored “centers” filling all of the feather but the outermost edge, which was tan-white. In contrast, the dark centers of these feathers in immature Ring-billed Gulls were concave-edged with pointed tips and largely restricted to the distal third of the feathers; thus, each feather was predominately white. These characters separate immature Mew from Ring-billed gulls Western Birds 16:147-150, 1985 147 NOTES and eliminate the possibility of “Common Gull” (L.c. cartus or L.c. kamchatkanensis) , as discussed by Lauro and Spencer (1980) and Grant (1982). Although both these records constitute first documented sightings for Utah (ac- cepted by the Utah Field Ornithologists Records Committee) , the occurrence of these gull species in Utah should come as no surprise. Both species winter commonly along the west coast, arriving there by lengthy migrations from their breeding grounds in arc- tic Canada and Alaska (AOU 1983). In addition, both species occur regularly in Nevada and Colorado (Kingery 1979) . Since the 13 November sighting, Thayer’s Gulls have been seen with increasing regularity in northern Utah. One was present near Logan, Cache Co., 10 to 12 December 1983. Another was at the Salt Lake City landfill 17 December 1983 (Figure 2) with up to four there from 19 February 1984 through at least the first week of March when the gulls began to disperse. Three more were located about 8 miles NW of Logan on 17 March 1984, with at least one remain- ing through 19 March. All were first year birds. In addition, this species was seen regularly during the fall of 1983 at American Falls Reservoir, Idaho, about 90 km north of the Utah border. The initial sighting was of three individuals on 6 November with four or five individuals present through at least 26 November (M.H. Tove and C.H. Trost). With the possible exception of one bird, all of these gulls were in first winter plumage. However, the only previous records from Idaho are of adults from Coeur d’Alene in the northernmost part of the state (Rogers 1977, 1978, 1981) . This point is significant because it suggests that Thayer’s Gulls (especially immatures) occur regular- ly and have been overlooked. This supposition is further supported by a general reluc- tance of many local observers to address the problems of immature gull identification, particularly when a species that is difficult to identify is involved. Likewise, a similar scenario applies to the Mew Gull. Although immatures are fairly distinct, given a knowledge of the correct field marks, the “traditional” field guides Figure 1. First winter Mew Gull at the Salt Lake City sanitary landfill, 9 February 1984. Note the very small bill, uniformly brown plumage and shape of the “centers” of the secondary coverts (see text) . Photo by Michael H. Tove 148 NOTES have been very misleading or even incorrect in their treatments. Thus, like Thayer’s Gull, Mew Gulls are probably more common than current records indicate. In sum- mary, it is suggested that increased observation of gull concentrations in the northern Great Basin region will reveal that Thayer’s Gulls are uncommon to rare and Mew Gulls are rare to occasional winter visitors. Mew Gulls were noted in exceptionally large numbers in the interior portions of Oregon (Mattocks 1984) and northern California (LeValley and Rosenberg 1984) during the winter of 1983-1984. The ef- fects of this incursion were noted as far east as coastal North Carolina where a first winter bird ( L.c . brachyrynchus) was observed (LeGrand 1984). It is likely that these occurrences relate to the severe weather patterns of fall 1983 (see Lehman 1984) , and the appearance of Utah’s first Mew Gull was perhaps related to this incursion. The following individuals were corroborating observers and provided data pertain- ing to the duration of stay of the birds: Keith Archibald, John and Terry Barnes, Mark Bromley, Don Hadley, Steve Hedges, Sue Hinde, Bill Hunter, Mark Leppert, Ella Sorensen, Merrill Webb. Thanks are extended to Keith L. Dixon who reviewed the manuscript and made several helpful suggestions. LITERATURE CITED American Ornithologists’ Union. 1983. Check-list of North American birds. 6th ed. Am. Ornithol. Union, Lawrence, KS. Conover, M R., B.C. Thompson, R E. Fitzner & D.E. Miller. 1979. Increasing populations of Ring-billed and California gulls in Washington state. West. Birds 10:31-36. Farrand, J., Jr., ed. 1983. The Audubon Society master guide to birding. No. 2: Gulls to dippers. Alfred Knopf, New York. Figure 2. First winter Thayer’s Gull at the Salt Lake City sanitary landfill, 17 December 1983. This individual was darker than average but still paler in flight than an immature Herring Gull. Note the whitish remiges from beneath and the lack of contrasting dark primaries on the upper wing. Photo by Michael H. Toue 149 NOTES Fussell, J.O., III, M.H. Tove & H.E. LeGrand, Jr. 1982. Report of six recent sightings of Iceland Gull in North Carolina with comments on problems of field identification. Chat 46:57-71. Gosselin, M. & N. David. 1975. Field identification of Thayer’s Gull ( Larus thayeri ) in eastern North America. Am. Birds 29:1095-1066. Grant, P.J. 1982. Gulls: a guide to identification. Buteo Books, Vermillion, SD. Kingery, H.E. 1979. Mountain West. Am. Birds 33:200,301. Lauro, A.J. & B.J. Spencer 1980. A method for separating juvenile and first winter Ring-billed Gulls (Larus delawarensis) and Common Gulls ( Larus canus) . Am. Birds 34:111-117. LeGrand, H.L., Jr. 1984. The southern Atlantic coast region. Am. Birds 38:305-308. Lehman, P. 1980. The identification of Thayer’s Gull in the field. Birding 12:198-210. Lehman, P. 1984. The changing seasons: the winter of 1983- 1984— “the Siberian express.” Am. Birds 38:287-292. LeValley, R. & K.V. Rosenberg. 1984. Middle Pacific coast region. Am. Birds 38:352-356. Mattocks, P. , Jr. 1984. Northern Pacific coast region. Am. Birds 38:349-351. Rogers, T.H. 1977. Northern Rocky Mountain-intermountain region. Am. Birds 31:353. Rogers, T.H. 1978. Northern Rocky Mountain-intermountain region. Am. Birds 32:378. Rogers, T.H. 1981. Northern Rocky Mountain-intermountain region. Am. Birds 35:320. Scott, S.L., ed. 1983. Field guide to the birds of North America. National Geographic Society, Washington, DC. Accepted 5 January 1985 Mew Gulls, first winter Sketch by Jonathan Alderfer 150 NOTES A RECORD OF PRETERRITORIAL COPULATION BY SANDHILL CRANES CARROLL D. LITTLEFIELD, Malheur Field Station, Box 260-E, Princeton, Oregon 97721 The Malheur- Harney Lakes Basin, Harney Co., Oregon, is an important traditional spring stopover area for the Pacific Flyway Population of Lesser Sandhill Cranes ( Grus canadensis canadensis) . Located in southeast Oregon, mowed and flooded meadows south and east of Burns provide excellent feeding, loafing, and roosting habitat for a majority of the 20,000 to 23,000 cranes in the population (Littlefield and Thompson, Proc. Crane Workshop 3:288-294, 1981). Individual birds remain in the basin from several days to a few weeks before continuing north to nesting regions in southwest Alaska. Migrants begin arriving in southeast Oregon in late February, peak in early April, and most have departed by early May. Herter (M.S. thesis, Univ. Alaska, College, Alaska, 1982) reported that members of the population arrived in southeast Alaska on 22 April 1979 and 19 April 1980; peak numbers occurred during the last week in April, with most flocks gone by mid-May. Cranes arrive in western Alaska in early May and nest initiation has been observed in mid-May (Boise, M.S. thesis, Univ. Alaska, College, Alaska, 1977). Considering Lesser Sandhill Cranes begin nesting about 2 weeks after arriving on their territories, copulation may regularly occur during migra- tion. Here 1 report on copulation by a pair of Lesser Sandhill Cranes at least 3500 km from the nearest known nesting area. While examining cranes for neck collars about 3 km south of Burns, I observed the Lesser Sandhill Crane pair copulate. The incident occurred about 0925 on 9 April 1983, Weather conditions at the time were characterized by snow showers and low overcast, after a minimum temperature slightly below 0°C (NOAA-Burns, Oregon). About 500 lessors were feeding together in a mowed meadow when the male assumed precopulatory behavior. The female became receptive as the male ap- proached, and coition occurred shortly thereafter. This was the first known record for copulation by this subspecies in southeast Oregon, and the first I am aware of for the species in the early phases of migration. No intensive behavioral studies of Lesser Sandhill Cranes have been conducted in this region; therefore, the regularity of copulation has not been ascertained. However, since the subspecies has a short time period for the nesting and brooding cycle, preterritorial copulation may be an adaption for successful reproduction at far northern latitudes. Accepted 11 July 1985 FIELD ASSISTANTS NEEDED Two volunteers are needed to help collect nesting and movement data on Prairie Falcons in western Wyoming. Food and field housing will be provided. Field work begins in early May and runs to mid-July. Volunteers are asked to stay at least 2 weeks (preferably 3 to 4). Some experience in handling birds or rock climbing is preferred. If interested, send a brief resume to: Bob Hitchcock, Wyoming Fish and Wildlife Coop. Unit, Box 3166, University Station, Laramie, Wyoming 82071. Phone: office (307) 766-2322, home (307) 721-2940. Western Birds 16:151, 1985 151 DUTCH BIRDING Quarterly journal for every keen birder! □ Excellent papers on identification, distribution, movements and behaviour of Palearctic birds. □ Latest news on rare birds in the Netherlands and Belgium. □ In English or with English summaries. □ Well produced with numerous high quality photographs. Ask for a free sample copy from Peter de Knijff, Dutch Birding Association, Postbus 473, 2400 AL Alphenaanden Rijn, Netherlands. is a 100 page workbook which critiques and adds information to the reuised edition of the Robbins et al. field guide. Euen if you use the NGS guide it mill inform and may surprise you. 152 available from RICH ST ALLCUP Box 36. Inverness. Cl 94937 $ 7.00 postpaid < Californians add 6% tax ) Volume 16, Number 3, 1985 Eighth Report of the California Bird Records Committee Joseph Morlan 105 Roadside Raptor Census in the San Jacinto Valley of Southern California Michael D. McCrary, Robert L. McKernan, William D. Wagner and Ross E. Landry 123 White Terns on Oahu Produce Siblings Five Months Apart Dorothy H. Miles 131 Treasurer’s Report Garth Alton 142 NOTES Vocalizations of the Black-headed Grosbeak Gary Ritchison 143 Unusual Western Bluebird Eggs Dauid Hayes 146 First Utah Records of Thayer’s and Mew Gulls With Comments on Their Regional Distribution and Status Michael H. Toue 147 A Record of Preterritorial Copulation by Sandhill Cranes Carroll D. Littlefield 151 Cover photo by William Ervin: Female Mountain Bluebird (Sialia cur- rucoides), at nest hole, Grand Teton National Park, Wyoming, June 1983. Manuscripts should be sent to Alan M. Craig, P.O. Box 254, Lakeview, CA 92353. For matters of style consult Suggestions to Contributors to Western Birds (6 pp. mimeo available at no cost from the Editor) and Council of Biology Editors Style Manual 4th edition, 1978 (available from the American Institute of Biological Sciences, 1401 Wilson Boulevard, Arlington, VA 22209 for $12.00). Papers are desired that are based upon field studies of birds, that are both understand- able and useful to amateurs, and that make a significant contribution to scientific literature. Appropriate topics include distribution, migration, status, behavior, ecology, population dynamics, habitat requirements, the effects of pollution, the techniques for identifying, censusing, sound recording and photographing birds in the field. Papers of general interest will be considered regardless of their geographic origin, but particularly desired are papers dealing with studies accomplished in or bearing on Rocky Mountain stat.es and provinces westward, including Alaska and Hawaii, adjacent portions of the Pacific Ocean and Mexico, and western Texas. Reprints can be ordered at author’s expense from the Editor when proof is returned or earlier. Good photographs of rare and unusual birds, unaccompanied by an article but with caption including species, date, locality and other pertinent information, are wanted for publication in Western Birds. Submit photos and captions to Photo Editor. WESTERN BIRDS Quarterly Journal of Western Field Ornithologists President: Laurence C. Binford, 985 Emily Avenue, Rohnert Park, CA 94928 Vice-President: Tim Manolis, 3532 Winston Way, Carmichael, CA 95608 Treasurer/ Membership Secretary: Art Cupples, 3924 Murrietta Ave., Sherman Oaks, CA 91423 Recording Secretary: Jean-Marie Spoelman, 4629 Diaz Drive, Fremont, CA 94536 Circulation Manager: Jerry R. Oldenettel, 4368 37th Street, San Diego, CA 92105 Directors: Laurence C. Binford, Peter Gent, Virginia P. Johnson, John S. Luther, Guy McCaskie, Timothy Manolis, Narca Moore-Craig, Joseph Morlan, Janet Witzeman Editor: Alan M. Craig, P.0, Box 254, Lakeview, CA 92353 Associate Editors: Cameron Barrows, Tim Manolis, Narca A. Moore-Craig, Dale A. Zimmerman Layout Artist: Virginia P. Johnson Photo Editor: Bruce Webb, 5657 Cazadero, Sacramento, CA 95822 Review Editor: Richard E. Webster, P.O. Box 6318, San Diego, CA 92106 Editorial Board: Robert Andrews, Alan Baldridge, William H. Behle, Andrew J. Berger, Laurence C. Binford (Chairman), Jeanne A. Conry, David F. DeSante, Jon L. 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Make checks payable to Western Field Ornithologists. A 15% commission is allowed for agencies. WESTERN BIRDS Volume 16, Number 4, 1985 OCCURRENCE AND IDENTIFICATION OF THE YELLOW-BELLIED FLYCATCHER ON SOUTHEAST FARALLON ISLAND, CALIFORNIA DAVID F. DESANTE, Point Reyes Bird Observatory, 4990 Shoreline Highway, Stinson Beach, California 94970 NED K. JOHNSON, Museum of Vertebrate Zoology and Department of Zoology, University of California, Berkeley, California 94720 RON LEVALLEY, Point Reyes Bird Observatory, 4990 Shoreline Highway, Stinson Beach, California 94970 (present address: 1876 Ocean Drive, McKinley ville, Califor- nia 95521) ROBERT P. HENDERSON, Point Reyes Bird Observatory, 4990 Shoreline Highway, Stinson Beach, California 94970 The occurrence in western North America, particularly in California, of numerous individuals of most migratory species of eastern North American passerines has been abundantly documented (McCaskie et al. 1979, Rober- son 1980, Garrett and Dunn 1981). Because of its fortuitous location, size, topography and vegetation, and because of the continuous year-round presence of personnel from the Point Reyes Bird Observatory (PRBO), Southeast Farallon Island, 42 km west of San Francisco, California, has pro- duced an inordinately large number of records of eastern passerines (DeSante and Ainley 1980, DeSante 1983). Eastern flycatchers of the genus Empidonax, however, with the exception of the Least Flycatcher (£. minimus), are represented there and elsewhere in western North America by very few documented records. Here we report two occurrences of the Yellow-bellied Flycatcher (E. flaviventris) on Southeast Farallon Island, the first of which constitutes the first record in California (Roberson 1980). In ad- dition, we present some new information bearing on the identification of this species. On 16 September 1976, at about 1530, a Yellow-bellied Flycatcher was captured by LeValley in a Heligoland trap surrounding a prostrate introduced Monterey Pine ( Pinus radiata). The bird was immediately suspected of being E. flaviventris by virtue of its very bright plumage relative to that of three Western Flycatchers (£. difficilis), two of which were captured and banded, present that day. With the bird in hand, the following description was taken: Top of head, back, rump and upper tail coverts green, tinged with yellow. Eye ring pale yellow. Chin yellowish-gray. Center of throat bright yellow, sides of Western Birds 16:153-160, 1985 153 YELLOW-BELLIED FLYCATCHER throat grayish-green. Chest grayish-green, abdomen and vent bright yellow. Wings dark blackish-brown with yellow (not buffy-orange) wing bars. Underside of wing at bend of wrist sulfur-yellow (not buff). Tail dark blackish-brown. Bill blackish above, flesh-colored below. Mouth lining orange. Legs blackish. Sixth primary slightly cut out on outer web. Measurements: wing (chord measured with standard wing rule), 62 mm: primary 10, 55 mm; primary 9. 62 mm; primary 8. 62 mm; primary 7, 62 mm; primary 6, 58.5 mm: primary 5. 54 mm; primary 4. 52 mm; primary 3, 51 mm. Tail (measured with calipers from the insertion of the central rectrices to the tip of the longest rectrix on the folded tail), 48.8 mm. The individual was in juvenal plumage and had an incompletely pneumatized skull (class 1 on a scale of 0 to 3, with 3 being completely pneumatized). It showed no molt, had no fat, and weighed 9.9 gm. It was banded with USF&WS band 1420-39697, photographed and released. It was not seen again. The written report on this individual was given No. 13-1977 by the California Bird Records Committee (C.B.R.C.) of the Western Field Ornithologists. On 27 September 1983, at approximately 1350, an Empidonax flycatcher was found by Ray Aker in a mist net located on the leeward side of the U.S. Coast Guard house near two fallen Monterey Cypresses (Cupressus macrocarpa) . While removing the bird from the net, the rectrices were ac- cidentally plucked. Eight rectrices were later recovered. Henderson recog- nized the bird as a possible Yellow-bellied Flycatcher and took the following description: Head, back, rump and upper tail coverts Empidonax green. Crown slightly darker than back as a result of dark centers on crown feathers. Face rather uniformly colored, the green of auricular area not distinct from postauricular, malar or superciliary areas. Throat generally pale yellow, whitish on chin. A grayish-green wash across upper breast. Remainder of underparts yellow, brightest on lower throat and upper abdomen and palest on lower abdomen and flanks. Undertail coverts whitish washed with yellow. Eye ring pale yellow, thin and fairly uniform in width, only slightly pointed behind eye. Anterior wing bar pale yellow slightly washed with buff; posterior wing bar whitish with a yellowish wash, strongest at tips. Secondaries and tertials crisply margined on outer edges and tips with yellowish-white, the margins on tertials broad and boldly contrasted to the remainder of wing which was dark brownish-black. Underside of bend of wing at the wrist yellowish. Tail dark blackish-brown. Bill blackish above, pale fleshy-orange below with a smoky tinge toward sides and tip. Mouth lining orangish-yellow. Legs blackish. Sixth primary slightly cut out, Although the records on the original data sheet state that the bird had a fully pneumatized skull (skull class 3) , the plumage and shape of rectrix tips (Johnson 1963, 1974) indicate that it was a juvenal. The bird showed no molt, had a trace of fat, and weighed 8.9 gm. It was banded with USF&WS band 1480-03392, photographed by Keith Hansen, and released. It was seen once again later that day. On the following day, 28 September, the bird was netted on four different occasions. Late in the day the bird was found in the Heligoland trap in weakened condition; at approximately 1600 it was found dead. The individual was prepared as a study skin by Larry Spear and deposited in the collections of the California Academy of Sciences (CAS) , San Francisco (71430). The bird proved to be a female. 154 YELLOW-BELLIED FLYCATCHER ANALYSIS OF MEASUREMENTS The tentative field identifications of C.B.R.C. record 13-1977 and CAS specimen 71430 as £. flaviuentris are here corroborated by analyses of the shape of the wing tip (Figure 1) and by the ratio of the length of primary 5 plotted against tail length (Figure 2). The comparison in both analyses is be- tween the Yellow-bellied and Western flycatchers, the two species of Em- pidonax most likely to be confused. In the absence in any collection of an adequate series of correctly-sexed fall juvenal Western Flycatchers, we use the wing and tail measurements of first-year specimens taken from Johnson (1974). This procedure is acceptable because first-year birds retain the juvenal rectrices and remiges through the post-juvenal (first prebasic) molt. Therefore, measurements for the juvenal-immature and first-year age categories are of feathers of the same generation that can be directly compared. As Figure 1 demonstrates, £. flaviuentris and £. difficilis have fundamen- tally different wing shapes. The wing tip of £. flaviuentris is comprised of only three primaries, numbers 9, 8 and 7, and hence is more pointed, whereas that of £. difficilis is composed of four primaries, numbers 9, 8, 7 and 6, and thus is more rounded. Furthermore, each of the outer four primaries (numbers 10 through 7) of the Yellow-bellied Flycatcher averages slightly longer than in the Western Flycatcher, whereas each of the next three primaries (numbers 6 through 4) averages considerably shorter. The measurements of C.B.R.C. record 13-1977 (given above) and those of CAS 71430 (taken by Johnson; primary 10, 54.4 mm; 9, 61.2; 8, 62.4; 7, 61.7; 6, 59.0; 5, 54.4; 4, 51.7) clearly demonstrate that both birds represent £. flaviuentris. Only for record 13-1977 is there a discrepancy. In this in- dividual, the value for primary 9 is apparently faulty. It is approximately 1.5 mm longer than would be expected for an individual with this wing shape. This kind of error occurs easily when one attempts refined measurements on a living bird. No species of Empidonax has the sharply truncated wing tip that the field measurements of this individual suggest. All other values for this bird agree with those expected for £. flaviuentris. The length of primary 5, the wing feather character differing the most in average value in young females of the two species, can be combined with tail length in a scatterplot to differentiate between the Yellow-bellied and Western flycatchers (Figure 2). This ratio clearly shows that C.B.R.C. 13-1977 represents £. flaviuentris. Analysis of CAS 71430 by this means is more dif- ficult because the tail was plucked. However, from the longest rectrix saved (left number 6), we estimate a tail length of 51.3 mm for this bird. This value was obtained by measuring the total lengths of several individual rectrices detached from specimens in the Museum of Vertebrate Zoology and com- paring these values with the standard tail lengths of the same specimens taken prior to feather plucking. This technique indicates that approximately 5 mm of each rectrix is embedded in the uropygium of the body and. therefore, is not included in the usual measurement of tail length, which is taken from the insertion of the central pair of rectrices. The ratio of the length of primary 5 to tail length again places CAS 71430 with £. flaviuentris . well separated from the clump of values for the sample of £. difficilis. 155 YELLOW-BELLIED FLYCATCHER (n = 6) Empidonax difficilis • ( n =10) Empidonax flaviventris o C.B.R.C. record 13-1977 CAS specimen 71430 ({ I st yr. females) (Juv.-Imm. females) x A Number of Primary Figure 1. Quantitative appraisal of wing shape in young female Empidonax difficilis and E. flaviventris, based on the lengths of the outer seven primaries. Technique of measurement is described in Johnson (1963:90-91). Measurements are of fully grown primaries representing the juvenal generation of feathers. Values obtained in the field for C.B.R.C. record 13-1977, and in the museum for specimen CAS 71430, are compared with means of samples of the Western and Yellow-bellied flycatchers. The stippling serves to outline the general shape of the wing to be expected in young female E. flaviventris. 156 YELLOW-BELLIED FLYCATCHER DISCUSSION The Yellow-bellied Flycatcher breeds in boreal coniferous forest across much of Canada, west to northern British Columbia {east of the Rocky Mountains) , and south to northern North Dakota and the Appalachians of northeastern Pennsylvania. It winters primarily in tropical lowland forests in eastern and southern Middle America and migrates regularly through the eastern United States, west to the central Great Plains and central Texas, and casually west to eastern New Mexico and western Texas (American Or- nithologists’ Union 1983). The only verified western extralimital records, other than those presented here, are of single individuals collected at Tucson, Arizona, on 22 September 1956 (Phillips et al. 1964) and at Coal Empidonax difficilis • E mpidonax flaviventris ° C.B.R.C. record 13-1977 CAS specimen 71430 (I st yr. females) Mean -f- ( Juv.-Imm.females) Mean x A Figure 2. Scatterplot of values of length of primary 5 versus length of tail in samples of young female Empidonax difficilis and E. flaviventris. See text for method of deter- mination of tail length of specimen CAS 71430. 157 YELLOW-BELLIED FLYCATCHER Creek near the Yukon River in east-central Alaska on 28 July 1966 (White and Haugh 1969), The Yellow-bellied Flycatcher probably occurs more regularly in western North America than these very few records suggest. Its breeding and win- tering ranges and migration routes are very similar to those of a number of eastern species of wood warblers ( Parulinae ) that occur regularly as vagrants in fall and, to a lesser extent, in spring in coastal California. The breeding and wintering ranges of the Black-throated Green Warbler ( Dendroica uirens) perhaps most closely approximate those of the Yellow-bellied Flycatcher. This warbler, however, through 1979, was represented by approximately 110 fall and 18 spring occurrences in California (Roberson 1980), including 6 each in fall and spring on Southeast Farallon Island during the 8-year period 1968-1975 (DeSante and Ainley 1980). The Cape May (Dendroica tigrina), Bay-breasted (D. castanea), Mourning (Oporornis Philadelphia) and Canada ( Wilsonia canadensis) warblers also have breeding ranges similar to that of the Yellow-bellied Flycatcher, although they tend to winter somewhat farther south and/or east. During the eight-year period of 1968-1975, these four species of warblers were represented by, respectively, 8, 10, 5 and 10 fall records and 13, 13, 0 and 3 spring occurrences on Southeast Farallon Island (DeSante and Ainley 1980) . Clearly, the Yellow-bellied Flycatcher has been recorded much less regularly than these species of warblers. Part of the reason for the apparent scarcity of the Yellow-bellied Flycatcher (and, presumably, some other eastern species of Empidonax flycatchers) in western North America, must certainly be the extreme difficulty of distinguishing individuals from the regularly occurring species of Empidonax, especially the very common and very similar Western Flycatcher (E. difficilis). It is also likely, however, that E. flaviventris is in fact an extremely rare vagrant to California. Fully 224 of the 326 individual fall Western Flycat- chers that were recorded on the Farallones during 1968-1975 were scrutin- ized in the hand and banded. None showed characters suggestive of E. flaviventris. Probably, the species has not been overlooked on the Farallones in recent years. What then accounts for the scarcity of vagrant Yellow-bellied Flycatchers relative to species of wood warblers with similar ranges? Although the answer is unknown, it is worth mentioning that nine-primaried passerines (emberizids, including parulids) have been shown to be proportionally more common as vagrants on the Farallones than ten-primaried passerines (tyran- nids, mimids, thrushes and vireonids) with similar breeding and wintering ranges (DeSante and Ainley 1980). Among non-parulids, perhaps the Philadelphia Vireo (Vireo philadelphicus) has breeding and winteringranges and migration routes most similar to those of the Yellow-bellied Flycatcher. Through 1979, this vireo was represented by only 39 fall and 5 spring occur- rences in California (Roberson 1980). During the eight-year period 1968-1975, it was recorded on the Farallones only once in fall and once in spring. The Philadelphia Vireo, therefore, seems to occur in California with only about f 6 -% of the abundance of the Black-throated Green Warbler. Yet its abundance on the Farallones is not much different from that of the Yellow- bellied Flycatcher which has not yet been definitely recorded on the Califor- nia mainland (a recent sight record from Point Reyes, Marin County, has yet 158 YELLOW-BELLIED FLYCATCHER to be reviewed by the C.B.R.C.). We can conclude, therefore, that the Yellow-bellied Flycatcher has probably been overlooked on the California mainland. The Least Flycatcher has occurred much more commonly than the Yellow-bellied Flycatcher, both on the Farallones [23 fall and 4 spring, 1968-1975 (DeSante and Ainley 1980)] and in California as a whole [53 fall and 11 spring through 1979 (Roberson 1980)]. The Least Flycatcher, however , breeds fairly commonly throughout British Columbia west of the Rockies and appears to be recently expanding its breeding range southwestward to include Washington, eastern Oregon and even northern California where it apparently bred in 1984 (Campbell and LeValley 1984). Its abundance, therefore, should be compared with that of such parulids as Blackpoll Warbler (Dendroica striata: 220 fall and 20 spring on the Farallones 1968-1975; 1333 fall and 72 spring in California through 1979), Tennessee Warbler ( Vermivora peregrina: 57 fall and 43 spring Farallones: 684 fall and 211 spring California), and Magnolia Warbler (Dendroica magnolia : 34 fall and 37 spring Farallones; 218 fall and 107 spring Califor- nia) that also breed west of the rockies in British Columbia (DeSante and Ainley 1980, Roberson 1980) . Clearly, the Least Flycatcher is less abundant both on the Farallones and in California as a whole than these parulids. Although the field identification of vagrant Yellow-bellied Flycatchers in western North America is extremely difficult at best and should not be generally encouraged, some observations prompted by the Farallon occur- rences seem appropriate. Both Farallon individuals were immediately recognized as E. flauiventris, once in the hand, by their overall bright green upperparts and distinctly yellow eye rings, wing bars, and underside of the bend of the wing, as compared to the duller olive-green or brownish-olive upperparts. whiter, less yellow eye rings and distinctly buffy wing bars and bend of the underwing of fall juvenal £. difficilis. Another striking characteristic, displayed by both Farallon birds and by virtually all fall juvenal E flauiventris in the Museum of Vertebrate Zoology and the California Academy of Sciences, is the extensive bright yellowish-white edgings to the secondaries and tertials that contrast boldly with the blackish remiges and wing coverts. These edgings are buffy or dirty whitish and more restricted in E. difficilis and contrast less with the paler and browner remiges and wing coverts of the Western Flycatcher. Roberson (1980), in discussing the iden- tification of Empidonax flycatchers, stated that the eye ring of E. flauiventris is round rather than strongly teardrop-shaped or almond-shaped behind the eye as in E. difficilis. In both examples of E. flauiventris from the Farallones, the eye ring was slightly pointed behind the eye but not really teardrop- shaped. In addition, the eye rings of both Farallon Yellow-bellied Flycatchers were distinctly narrower than in typical E. difficilis. which probably have the widest and most teardrop-shaped eye rings of all North American species of Empidonax. These characteristics are subtle and subjective and have yet to be properly tested in the field. Nonetheless, a fall Empidonax in western North America that shows bright green upperparts, bright yellow underparts, a rather narrow yellow eye ring, only slightly, if at all, pointed behind the eye, distinctly yellowish wing bars, and extensive bright yellowish-white secondary and tertial edgings that contrast sharply with blackish remiges and wing 159 YELLOW-BELLIED FLYCATCHER coverts would certainly deserve scrutiny and, if possible, capture and preser- vation for detailed study. ACKNOWLEDGMENTS We sincerely thank the members of the Point Reyes Bird Observatory for financial support and the Farallon Patrol of the San Francisco Bay Chapter of the Oceanic Society for logistic support. We also thank Laurence C. Binford for his helpful comments on the manuscript. Gene M. Christman drafted the final versions of the figures. This is PRBO Contribution 176. LITERATURE CITED American Ornithologists’ Union. 1983. Check-list of North American birds. Sixth ed. Am. Ornithol. Union, [Washington, DC]. Campbell, K.F. & R. LeValley. 1984. The summer season: Middle Pacific Coast region. American Birds 38:1056-1060. DeSante, D.F. 1983. Annual variability in the abundance of migrant Iandbirds on Southeast Farallon Island, California. Auk 100:826-852. DeSante, D.F. & D.G. Ainley. 1980. The avifauna of the South Farallon Islands, California. Studies Avian Biol. 4. Garrett, K. & J. Dunn. 1981. The birds of southern California, status and distribution. Los Angeles Audubon Soc., Los Angeles. Johnson, N.K. 1963. Biosystematics of sibling species of flycatchers in the Empidonax hammondii-oberhoheri-wrightii complex. Univ. California Publ. Zool. 66:79-238. Johnson, N.K. 1974. Molt and age determination in Western and Yellowish fly- catchers. Auk 91:111-131. McCaskie, G., P. DeBenedictis, R. Erickson & J. Morlan. 1979. Birds of northern California, an annotated field list. Golden Gate Audubon Soc., Berkeley. Phillips, A.R., J. Marshall & G. Monson. 1964. The birds of Arizona. Univ. Arizona Press, Tucson. Roberson, D. 1980. Rare birds of the West Coast. Woodcock Publ., Pacific Grove, CA. White, C.M. & J.R. Haugh. 1969. Recent data on summer birds of the Upper Yukon River, Alaska, and adjacent part of the Yukon Territory, Canada. Can. Field- Naturalist 83:257-271. Accepted 24 October 1985 160 REPRODUCTION OF MOUNTAIN BLUEBIRDS IN SOUTHCENTRAL MONTANA JON E. SWENSON, Montana Department of Fish, Wildlife and Parks, 1001 Ridgeway Drive, Livingston, Montana 59047 Mountain Bluebirds ( Sialia currucoides ) occupy an extensive breeding range in western North America (Bent 1949) . They breed in a greater variety of habitats, including the Upper Sonoran, Transition, Canadian and Hud- sonian life zones, than other members of the genus (Power 1966, Herlugson 1978, Pinkowski 1979a). Although Ponderosa Pine ( Pinus ponderPsa) savannas are often used by breeding Mountain Bluebirds (Pinkowski 1979a), there are apparently no published reports of the reproductive biology of the species in Ponderosa Pine-dominated habitats. Here I report results of a 3-year study of Mountain Bluebird reproductive biology in a Ponderosa Pine savanna in southcentral Montana. STUDY AREA AND METHODS The study area is about 19 km north- northeast of Shepherd, Yellowstone County, in southcentral Montana, on unglaciated sedimentary plains with rolling topography formed primarily by erosion. Altitude is about 1200 m and annual precipitation averages 330 mm. Ponderosa Pine savanna dominated the study area. Common shrubs were Big Sagebrush ( Artemisia tridentata), Rocky Mountain Juniper ( Juniperus scopulorum) and Skunkbush Sumac ( Rhus trilobata) . Common grasses in- cluded Bluebunch Wheatgrass ( Agropyron spicatum) , Blue Grama (Bouteloua gracilis), Prairie Junegrass (Koeleria cristata) and blue grass ( Poa sp.). Broom Snakeweed ( Gutierrezia sarothrae) and Small Soapweed (Yuc- ca glauca) were common forbs. This habitat was similar to the Pinus ponderosa/ Artemisia tridentata habitat described by Jorgensen (1979). I studied the reproduction of Mountain Bluebirds during the summers of 1967, 1968 and 1969. Prior to the 1967 nesting season, 16 bluebird nest boxes were placed on the study area; these boxes were repaired as required. The nest boxes had inner dimensions of 12.7 x 12.7 x 20.3 cm, with an en- trance hole diameter of 4. 1 cm located 13.3 cm above the bottom of the box. Boxes were placed 1.3 to 1.6 m above the ground on living Ponderosa Pines (14) or fenceposts (2) along a triangularly shaped route about 2.25 km long. One natural nest, in a hollow stump, was included in this study. The nests were checked every few days between late March and late July- early August. A nesting attempt was defined as a nest receiving at least one egg. Clutch size referred to completed clutches with incubation underway. The date of clutch completion was the day the last egg was laid in the clutch. If not observed directly, this date was calculated by assuming a 13-day in- cubation, with incubation beginning on the day the last egg was laid (Power 1966) . Nest success was defined as the proportion of nesting attempts pro- ducing at least one fledged young. Bias in calculating nest success or nest density inherent in studies involving nest searches, as discussed by Miller and Western Birds 16:161-168, 1985 161 MOUNTAIN BLUEBIRD REPRODUCTION Johnson (1978), was not a factor in this study, since only the nest boxes and one natural cavity were checked for nests. Nesting attempts were divided into early and late nesting with a clutch completion date of 1 June separating the two groups. In 1967, however, when a late spring storm delayed the nesting, 12 June was used as the date of separation. “Late first broods” and “second broods,” distinguished by Power (1966), were lumped in this study because Mountain Bluebirds may move on and off the area during the nesting season and may renest in another box, as observed by Pinkowski (1977) in the Eastern Bluebird ( Sialia sialis ) , Mean values were tested for statistical difference by using two-tailed t-tests and frequency data were compared statistically with chi-squared tests using 2x2 contingency tables corrected for continuity (Snedecor and Cochran 1967). RESULTS ARRIVAL DATES AND NEST BOX UTILIZATION In 1967, four male Mountain Bluebirds were observed on 20 March. On my second visit, 25 March, eight males and three females were seen. 1 saw six males on 30 March 1969. These dates are probably near the date of first arrival on the study area because male Mountain Bluebirds usually arrive a few days in advance of the females (Criddle 1927). Each year of my in- vestigation, 11 early nesting attempts were made on the study area (Table 1) . REPRODUCTION The average date of clutch completion was influenced by the weather (Table 2) . In 1967, one clutch was completed on 24 April, but a late spring storm caused other pairs to stop building and wait until late May to complete their clutches. In 1969, a snow storm and frost in early June destroyed many first clutches, resulting in earlier renesting. Under normal conditions, mean early clutches (N = 21) were completed on the study area on 11 May (21 April-28 May) and late clutches (N = 8) on 22 June (19 June-2 July). Average clutch size for early clutches (N = 31) was 5.23 ±0.67 eggs per completed clutch. This clutch size differed significantly (P<0.05) from late clutches (N = 18), which averaged 4.72 ±0.67 eggs. Hatching success of completed clutches was similar (P>0.3) for eggs in early and late clutches (Table 1) and averaged 71% (N = 222). Human disturbance (capturing the female for banding) and predation were the most important causes of failure of eggs to hatch for early and late clutches, respectively, but the causes of failure varied from year to year (Table 3) . The most common predators of bluebird eggs on this area were Deer Mice ( Perom^scus maniculatus) (Swen- son 1968) and House Wrens ( Troglodytes aedon), which destroyed eggs in five and two clutches, respectively, and caused the abandonment of these clutches. Of a total of 267 eggs examined on and near the study area, none were albinistic, compared to 8.3% of 108 eggs in northcentral Montana (Power 1966) and 6.1% of 837 eggs in Manitoba (Munro et al. 1981) . Albinism was 162 MOUNTAIN BLUEBIRD REPRODUCTION significantly less on my study area than on the other two areas (F<0.005). There was no statistical difference between the other two areas, however (P>0.9). One nest was counted as two nestings, both failures. It contained 10 eggs, which were never incubated, on 18 June 1968. This nest was probably a “dump nest,” with eggs contributed by two females, as has been previously observed in the Eastern Bluebird (Musselman 1935). Table 1. Summary of Mountain Bluebird reproductive parameters in a Ponderosa Pine savanna in southcentral Montana. Parameter 1967 1968 EARLY NESTS 1969 Total Nesting attempts (A) 11 11 11 33 Successful nests (B) 7 7 4 18 Nest success (B/A) 64% 64% 36% 55% Completed clutches (C) Eggs laid (complete 10 11 10 31 clutches) (D) 50 60(50)“ 52 162(152)“ Clutch size (D/C) 5.00 5.45 5.20 5.23 Eggs hatched (E) 28 43 34 105 Hatching success (E/D) 56% 86% 65% 69% Young fledged (F) 25 28(21)* 15 68 (6 1)* Nestling survival (F/E) Fledglings per successful 89% 49% 44% 58% nest (F/B) Fledglings per nesting 3.57 4.00 3.75 3.78 attempt (F/ A) 2.27 2.55 LATE NESTS 1.36 2.06 Nesting attempts (A) 3 8 C 8 19“ Successful nests (B) 2 3 2 7 Nest success (B/A) 67% 38% 25% 37% Completed clutches (C) Eggs laid (complete 3 7 8 18 clutches) (D) 13 33(18)“ 39 85(70)“ Clutch size (D/C) 4.33 4.71 4.88 4.72 Eggs hatched (E) 8 14 31 53 Hatching success (E/D) 62% 78% 79% 76% Young fledged (F) 8 13(9/9)" 10 31(27/48) Nestling survival (F/E) Fledglings per successful 100% 100% 32% 56% nest (F/B) Fledglings per nesting 4.00 4.33 5.00 4.43 attempt (F/A) 2.67 1.62 1.25 1.63 “Number of eggs of known hatching success. ''Number of young fledged from nests with known hatching success. “Excludes 3 nests of unknown outcome. ''(Number of young fledged/Number of young hatched) for nests of known hatching success and outcome. 163 MOUNTAIN BLUEBIRD REPRODUCTION Table 2. Average dates Montana.. Year 1967 1968 1969 “Sample size of Mountain Bluebird clutch First Clutches 24 May (11)“ 10 May (11) 11 May (10) completion in southcentral Second Clutches 22 June (2) 22 June (6) 10 June (6) Table 3. Causes of Mountain Bluebird egg hatching failure in southcentral Montana." Number of Eggs Dead Embryo Human Year Laid Hatched or Infertile Predation Disturbance" Desertion® EARLY CLUTCHES 1967 52 54 d 12 19 12 4 1968 50 86 4 0 10 0 1969 55 62 5 9 15 9 Total 157 67 7 10 12 4 LATE CLUTCHES 1967 13 62 0 38 0 0 1968 33 42 0 27 0 30 1969 39 79 10 10 0 0 Total 85 62 5 21 0 12 “All eggs, including those in incomplete clutches. "Female was captured and banded. “Female was not captured. ‘'Figures in this column, and in all columns to the right, are percentages. Table 4. Causes of Mountain Bluebird nestling mortality in southcentral Montana. No. of Young Mortality Factor Year Hatched Fledged Weather Predation Accident Unknown EARLY BROODS 1967 28 89“ 0 0 0 11 1968 43 49 0 9 0 42 1969 34 44 41 0 12 3 Total 105 58 13 4 4 21 LATE BROODS 1967 8 100 0 0 0 0 1968 9 100 0 0 0 0 1969 31 32 55 13 0 0 Total 48 56 35 8 0 0 “Figures in this column, and in all columns to the right, are percentages. 164 MOUNTAIN BLUEBIRD REPRODUCTION Table 5. Comparison of the frequency of clutch sizes and young fledged by clutch size in Mountain Bluebird nesting attempts in southeastern Montana (early clutches only) . Clutch Size Frequency (%)■ Young fledged per successful nest 3 4 5 6 3 3 61 32 2.00 2.00 4.56 3.29 “N =31. Average brood size at fledging for first broods (N = 18) was 3.78 ± 1.56 young and for second broods (N = 7) was 4.43 ±0.79 young. These brood sizes were not significantly different (P>0.3). Nestling survival was similar for both periods (P>0.9) and averaged 58% (N = 153). Adverse weather was the most commonly identified cause of nestling death for both brood periods, but it was a factor only in 1969 (Table 4) , when a snow storm struck in early June and the area received heavy rains in late June. Deer Mice were the pro- bable predators which destroyed two broods (Swenson 1968) . The number of young fledged per nesting attempt (Table 1) was higher for early nests (2.06) than late nests (1.63), but the difference was not significant (R>0.2) . During this study, 1 observed a total of 33 early nesting attempts and 22 late attempts, including attempts of unknown outcome. Assuming that as many bluebird pairs entered the study area as left it to renest, and that each late attempt was a renest, each pair renested an average of 0.67 (22/33) times. The average pair produced 2.06 young from the first nesting and 1.09 young (0.67 attempts x 1.63 young/attempt) from the second nesting, or 3.15 young per year. The most common early clutch size on the study area (5 eggs) was the most productive in terms of young fledged (Table 5). The reason that clutches of five were more productive than clutches of six was that survival of nestlings was significantly lower (P<0.001) in broods of six (67%, N = 30) than in smaller broods (94% , N = 72) . Only nestlings in successful nests were considered in this comparison. MOVEMENTS AND SITE FIDELITY I banded 1 adult male, 19 adult females and 89 young during this study. Because the birds were not color- marked, movement data could only be ob- tained by recapturing banded birds. Recaptures of two adult females sug- gested that the female Mountain Bluebirds returned to the study area the following year, but not necessarily to the same nest site. One female was banded as an adult in nest 1 in 1967, recaptured in nest 8 in 1968 (330 m from nest 1) and in nest 3 in 1969 (335 m from nest 8). Another female, banded as an adult in nest 4 in 1967 was recaptured in nest 14 in 1968 (390 m from nest 4) . These nest sites averaged about 350 m from the nest used the previous year. This distance is very similar to Pinel’s (1980) finding that 165 MOUNTAIN BLUEBIRD REPRODUCTION six Mountain Bluebirds, banded as adults, were recaptured an average of 400 m from the site of banding in the aspen parklands of Alberta. In 1969, different females used nest 4 for the first and second nestings, even though the first attempt was successful. Females became much more wary after banding; after being banded they left the nest box while I was still some distance from it. The difference in reac- tions to my approach between females which had been captured and those not previously captured that season was obvious. I captured 22 (71%) of 31 females completing early clutches but only 3 (17%) of 18 females completing late clutches, none of which had been captured previously that year. This dif- ference is highly significant (POO. 001). DISCUSSION The observation of 1 1 early nesting attempts each year on my study area suggested that territorial behavior may limit the number of bluebirds using available nest sites and that all available territories were filled, as has been found in the Eastern Bluebird by Pinkowski (1979a). That this occurred the first year suggested there was a shortage of natural nest sites on the study area or that the boxes were preferred to the available natural nest sites. Sub- jective observations on my study area suggested that there was a relative shortage of adequate natural cavities. Several Mountain Bluebirds in the vicinity of the study area were found nesting in cavities that opened upward and one was quite exposed. This type of cavity is selected against by Eastern Bluebirds (Pinkowski 1976). Both of the banded females recaptured in subsequent years had returned to the study area after nesting there unsuccessfully the previous year. This observation is in contrast to Pinkowski’s (1977) finding that all 47 Eastern Bluebirds that returned to his study area had nested there successfully the previous year. Also, the significantly more wary behavior of females com- pleting late clutches than that of females completing early clutches was most likely due to a large percentage of previously captured birds remaining on the area to renest. Although this conclusion is based on circumstantial evidence, I feel that it is strong enough to warrant the conclusion because of the marked change in female reactions to my approaches following banding. Pinkowski (1977) found that 66% of the female Eastern Bluebirds left his study area im- mediately after an unsuccessful nesting attempt, and that almost all successful birds stayed on the area. Mountain Bluebirds on my study area apparently showed a stronger degree of nest site fidelity than that found in Pinkowski’s (1977) study of Eastern Bluebirds. This difference is probably not due to behavioral dif- ferences between the species; Herlugson (1981) found that 68% of 22 suc- cessful female Mountain Bluebirds in Washington returned to the same ter- ritory and nest box the following year, compared to only two of five unsuc- cessful females. The apparent nest site fidelity in my area may have been due to a lack of suitable natural cavities. This theory was not tested, but was sup- ported by general observations on the scarcity of adequate natural nest sites, the rapid occupation of territories (occupation of nest boxes was gradual on Pinkowski’s study area) , the apparently low rate of movement from the area 166 MOUNTAIN BLUEBIRD REPRODUCTION during the nesting season, the return of females to the area even after nesting there unsuccessfully the previous year, and the occurrence of dump-nesting. If the nest site fidelity was as strong as the evidence suggested, the deter- mination of annual productivity per pair was probably accurate. This parameter is difficult to measure in most passerines (Pinkowski 1979b). I estimated that 67% of the pairs renested and produced an average of 3.15 young per pair per year. Power (1966) found that 50% of all successful pairs (31% of all pairs) renested on his study area and Rounds and Munro (1983) suggested that renesting was common. Estimating annual productivity as 1 did can greatly underestimate the actual productivity if movement from the study area for renesting is great and is biased towards unsuccessful pairs (Pinkowski 1979b). Cody (1966). modifying Lack (1947). postulated that, in nidicolous species in temperate regions, the average clutch size is probably determined ultimately by the average maximum number of young which the parents can successfully raise, based on the average food supply available in the area and season in question. This theory is not supported by the results of some studies (e.g. Middleton 1979). but it is supported by the results of my study, since the most young were fledged from the most common clutch size on my study area (5 eggs) . It appeared as though the adults may have had difficulty in providing enough food to rear broods of six as successfully as smaller broods. Mountain Bluebirds are very insectivorous, thus sensitive to short- ages of insects, and they increase the amount of hovering, an energetically costly foraging behavior, during times of higher nutritional needs, such as when feeding nestlings (Pinkowski 1979a. Power 1980. Herlugson 1982). ACKNOWLEDGMENTS I am grateful to my parents, Frank and Eva. Swenson, for their support and encouragement during this study. 1 also thank Benedict C. Pinkowski, Harry W. Power, John P. Weigand. Robert L. Eng. D. Paul Hendricks and Cameron Barrows for reading drafts of this paper and providing many helpful comments. This paper is dedicated to the memory of my friend and mentor. Don C. MacDonald. LITERATURE CITED Bent. A.C 1949. Life histories of North American thrushes, kinglets, and their allies. U.S. Natl. Mus. Bull. 196. Cody, M L. 1966. A general theory of clutch size. Evolution 20:174-184. Criddle. N. 1927. Habits of the Mountain Bluebird in Manitoba. Can. Field-Nat. 41:40-44. Herlugson. C.J. 1978. Comments on the status and distribution of Western and Mountain bluebirds in Washington. West. Birds 9:21-32. Herlugson, C.J. 1981. Nest site selection in Mountain Bluebirds. Condor 83:252-255. Hergulson. C.J. 1982. Food of adult and nestling Western and Mountain bluebirds. Murrelet 63:59-65. 167 MOUNTAIN BLUEBIRD REPRODUCTION Jorgensen, H.E. 1979. Vegetation of the Yellow Water Triangle, Montana. Montana Dept. Fish and Game Publ. Lack, D. 1947. The significance of clutch-size. Ibis 89:302-352. Middleton, A.L.A. 1979. Influence of age and habitat on reproduction of the American Goldfinch. Ecology 60:418-432. Miller. H.W. & D.H. Johnson. 1978. Interpreting the results of nesting studies. J. Wildl. Manage. 42:471-476. Munro, H.L., D.H. Munro & R.C. Rounds. 1981. Fertility of albinistic eggs of Moun- tain Bluebirds. Auk 98:181-182. Musselman, T.E. 1935. Three years of Eastern Bluebird banding and study. Bird- Banding 6:117-125. Pinel, H.W, 1980. Reproductive efficiency and site attachment of Tree Swallows and Mountain Bluebirds. Blue Jay 38:177-183. Pinkowski, B.C. 1976. Use of tree cavities by nesting Eastern Bluebirds. J. Wildl. Manage. 40:556-563. Pinkowski, B.C. 1977. Breeding adaptations in the Eastern Bluebird. Condor 79:289-302. Pinkowski, B.C. 1979a. Foraging ecology and habitat utilization in the genus Sialia. Pp. 165-190 in J.G. Dickson et al., eds. The role of insectivorous birds in forest ecosystems. Academic Press, New York. Pinkowski, B.C. 1979b. Annual productivity and its measurement in a multibrooded passerine, the Eastern Bluebird. Auk 96:562-572, Power, H.W. III. 1966. Biology of the Mountain Bluebird in Montana. Condor 68:351-371. Power, H.W, 1980. The foraging behavior of Mountain Bluebirds with emphasis on sexual foraging differences. Ornithol. Monogr. No. 28. Rounds, R.C. & H.L. Munro. 1983. Brood size of Eastern and Mountain bluebirds in Manitoba. J. Field Ornithol. 54:304-311. Snedecor, G.W. & W.G. Cochran. 1967. Statistical methods, 6th ed. Iowa State Univ. Press, Ames. Swenson, J.E. 1968, The Deer Mouse as a nest competitor and possible predator of the Mountain Bluebird. Blue Jay 26:214-215. Accepted 22 Ju/y 1985 168 NEARSHORE FLIGHTS OF SEABIRDS PAST YAQUINA ESTUARY, OREGON, DURING THE 1982 AND 1983 SUMMERS RANGE D. BAYER, Oregon Aqua-Foods, Inc., Newport, Oregon 97365 (present ad- dress: P.O. Box 1467, Newport, Oregon 97365) Although there have been several studies of seabird distributions off the Oregon and Washington coasts (e.g., Wahl 1975, Wiens and Scott 1975, Manuwal et al. 1979, Wahl et al. 1981, Matthews 1983, Wahl and Speich 1984) , research has not been directed to determining the net movement of seabirds flying nearshore along these coasts. Interpretations of flights can be equivocal, but Marchant (1977) has shown that systematic observations of nearshore flights can provide valuable information about seabird distributions and movements. I conducted this study to determine if selected seabirds, especially Com- mon Murres ( Uria aalge), exhibited significant net movements past the mouth of Yaquina Estuary. Dispersion or migration would be suggested by many more birds flying in one direction than another because if there were many watches, the numbers of birds flying to and from colonies or feeding areas should cancel each other out. STUDY AREA AND METHODS All observations were from a point about 0.2 km from land on the south jetty of Yaquina Estuary (44° 37’N, 124° 04’W), which is on the mid- Oregon coast in Lincoln County. During 5-min watches, I counted seabirds flying north or south through the field of view of a 20x telescope, which was pointed westward. The horizon of the sky was set near the top of the lower one-third of the field of view, and the telescope was 5-6 in above the water. Flying birds were observable to about 2-3 km offshore. I counted shearwaters (virtually all Sooty Shearwaters, Puffinus griseus, with occasional Fink- footed Shearwaters, P. creatopus ) , Fork-tailed Storm-Petrels (Oceanodroma furcata), Brown Pelicans (Pelecanus occidentalis) , Brandt’s ( Phalacrocorax penicillatus) and Pelagic (P. pelagicus ) cormorants, Common Murres and Pigeon Guillemots (Cepphus columba). During the June-September period, I conducted 124 watches in 1982 (mainly of shearwaters and murres) and 58 in 1983. Watches in 1982 were 10-25 min apart on 10 July and were a minimum of 56 min apart on other days; in 1983, there was one watch/day in June-August and 1-3 watches/day, 15-30 min apart, in September. Watches in 1983 were divided into different intervals for each species based on changes in a bird’s abundance. For example, watches for Common Murres were divided into four intervals (June- 15 July, 16-31 July, 1-18 August, and September) because the abundance of murres differed greatly among these intervals (see below) . To determine if net movements were significant, the numbers of birds flying north versus the numbers flying south during watches were tested with a two-tailed Wilcoxon paired-sample test (Zar 1974: 124-126). Western Birds 16:169-173, 1985 169 Table 1. Net number of shearwaters and Common Murres flying north past Yaquina Estuary, Oregon, during 5-min watches in 1982. The Wilcoxon paired-sample test was used to examine significance. P = probability; NS = not significant; a dash indicates no data available. NEARSHORE SEABIRD FLIGHTS rH LO LO H LO OOOOOOC/)C/)C/)CO oddddoZZZZ WWW v> 0> J- 3 2 c o E E o U CD cn e (0 DC JO u -f-* to 3 k* V « -£ I ? c cr — c QJ S Z MD VO ^ CO m o o i— i o cm r"t h h 00^ CO HCMCMOOOOO o^orfocsin odcsicMiincdcdcd 000 oo in cm uo — < CM T-H ot^ddincMo 000 0 co mo m —i Cl ' ' cm m cn o cn o ' ' ' ' Z d Z o V V o> • 4-1 <0 3 10 0) JO cn cn c 10 DC o o cn <0 3 u. Q I = c a 10 t-'r''t'»OCT'CT'— ‘OOMO CM H t-H i- 1 rH c .2 — 10 > l- CD (/) J3 o o o o-lo in o o o o o CO CM CM ^ — (OCOOCOO H rH C*sJ H rH rH rH H H rH iiiiiiitii ooaoooooam ocMin^tin^incM^r-* ^ o — mo mo mo r'- r-^ rH i— I i— ! o O O O O O O CM oo OM cn cn cn a 3333 0)333a^ O CM 00 O ! ~ CM CJM MO ^ MO i-H CM CM CO in rH , — I CM CO H NEARSHORE SEABIRD FLIGHTS RESULTS AND DISCUSSION In 1982, shearwaters were not common until August, and on the four cen- sus days in August and September their net movement was northward (i.e., the number of birds flying north was greater than the number flying south) each day and was significantly so on two of the days (Table 1). In 1983, shearwaters were first observed on 9 May, but there were fewer than 5/watch until 31 July. From then through September they commonly flew by, mainly northward (Table 2). The net number of shearwaters flying north in 1983 in the 30 July-September period was within the daily range of 1982 flights (Tables 1 and 2). Fork-tailed Storm-Petrels were not detected in 1982, but a net average of 1.1 flying north was observed in 1983 between 15 August and 5 September (Table 2) . They did not exhibit a significant northward trend (Table 2) . Their unusual nearshore abundance in 1983 was also noted along the southern Oregon coast (Evanich and Fix 1983). Brown Pelicans and cormorants both exhibited net averages of 0.1-0. 5/ watch flying north in 1983 (Table 2). The net number of pelicans flying north was barely significant, and the net number of cormorants flying north was insignificant (Table 2). In 1982, the magnitude of Common Murre flights often changed within a day, but the only watches with net southward movements were on 10 July (Table 1). The net flight directions were significantly northward each day in July and on 5 and 12 August (Table 1). Net northward rates on 28 July Table 2. Net number of birds flying north past Yaquina Estuary, Oregon, during 5-min watches from June to September 1983. The Wilcoxon paired-sample test was used to test significance. F. Storm-Petrel = Fork-tailed Storm-Petrel; Days = number of days of watches; P = probability; NS = not significant. Net number of birds Days Watches flying north per watch Taxon 1983 Period N N X SD Range P Sooty Shearwater Jun-29 Jul 23 23 0.3 1.0 <-2)-2 NS Sooty Shearwater 30 Jul-Sep 23 33 19.6 34.1 (-D-134 <0.01 F. Storm-Petrel Jun-14 Aug 30 30 0 0 0 NS F. Storm-Petrel 15 Aug-5 Sep > 7 8 1.1 2.5 (-4) -4 NS F. Storm-Petrel 6-30 Sep 9 18 0 0 0 NS Brown Pelican Jun-Sep 46 56 0.5 1.9 (-3)10 <0.10 Cormorant Jun-Sep 46 56 0.1 4.6 (-16) - 12 NS Common Murre Jun-15 Jul 15 15 0.7 44.9 (-75) -92 NS Common Murre 16-31 Jul 9 9 28.2 29.5 (-l)-89 <0.01 Common Murre 1-18 Aug 10 10 5.7 12.5 (-6)-32 NS Common Murre Sep 12 22 0 0 0 NS Pigeon Guillemot Jun-Jul 24 24 0.1 0.9 (-l)-3 NS Pigeon Guillemot 1-18 Aug 10 10 2.1 2.2 (-D-7 <0.02 Pigeon Guillemot Sep 12 22 0 0 0 NS 171 NEARSHORE SEABIRD FLIGHTS averaged almost 170/ watch (Table 1) , a rate of about 2000 murres flying north an hour. In 1983, murres most commonly flew by the jetties in June and July, but the only significant northward movements were in late July (Table 2) . Even during the peak flight period of 1983, the net rates of flights were never as great as during the same period in 1982 (Tables 1 and 2) . The differences between 1982 and 1983 may have been related to the 1983 El Nino as murres left the central Oregon coast much earlier in 1983 than 1982 (Bayer 1986) and both nesting success and adult survival of Common Murres along the Oregon coast was greatly reduced in 1983 (Graybill and Hodder 1985) . The significant northward movements of Common Murres in 1982 and 1983 occurred about the time that non-flying young of Oregon murres left nesting areas with their fathers to swim along the coast (Scott 1973). These flights could be of female and unsuccessfully nesting male murres migrating to the Strait of Juan de Fuca between Vancouver Island and Washington State, where many murres from Oregon and perhaps California arrive by September (Manuwal et al. 1979: 58-59). Pigeon Guillemots infrequently flew past the jetties and showed a significant net movement (northward) only in the 1-18 August 1983 period (Table 2). There is no information on where Oregon Pigeon Guillemots migrate or disperse to after their nesting season, but perhaps they accompany the Com- mon Murres to the Strait of Juan de Fuca. CONCLUSIONS All seabirds in this study showed net northward movements, but the movements were significant for only a few taxa during parts of the summer. Net movements in some areas can be the normal daily pattern (e.g., Sharrock 1973 cited in Marchant 1977), but Marchant (1977) observed that net movements may also be good indicators of bird migrations. In this study, it was not possible to prove conclusively that the significant net movements represented migration. ACKNOWLEDGMENTS I thank Dennis Paulson and Harry B. Nehls for constructive comments on an earlier draft of this paper. I am also grateful to Bill McNeil, Vern Jackson, Rob Lawrence, Mike Bauman and Andy Rivinus of Oregon Aqua-Foods for facilitating the logistics and funding of this project. LITERATURE CITED Bayer, R.D. 1986. Seabirds near an Oregon estuarine salmon hatchery in 1982 and during the 1983 El Nino. Fishery Bulletin 84(2), in press. Evanich, J. & D. Fix. 1983. Highlights from the field notes: summer 1983. Oregon Birds 9:91-100. Graybill, M.R. & J. Hodder. 1985. Effects of the 1982-83 El Nino on reproduction of six species of seabirds in Oregon. Pp. 205-210 in W.S. Wooster & D.L. Fluharty, eds. El Nino North: Nino effects in the Eastern Subarctic Pacific Ocean. Washington Sea Grant Program, Univ. Washington, Seattle. 172 NEARSHORE SEABIRD FLIGHTS Manuwal. D.A., T.R. Wahl & S.M. Speich. 1979. The seasonal distribution and abundance of marine bird populations in the Strait of Juan de Fuca and northern Puget Sound in 1978. NOAA Tech. Memo. ERL MESA-44. Marchant. S. 1976. A seawatch on the southern coast of New South Wales. Emu 76:9-18. Matthews. D.R. 1983. Feeding ecology of the Common Murre. Uria aaige. off the Oregon coast. M.S. thesis. Univ. Oregon. Eugene. Scott. J.M. 1973. Resource allocation in four syntopic species of marine diving birds. Ph.D. thesis. Oregon State Univ.. Corvallis. Sharrock. J.T.R.. ed. 1973. The natural history of Cape Clear Island. Berkhamsted: Poyser. Wahl. T.R. 1975. Seabirds in Washington's offshore zone. West. Birds 6:117-134. Wahl. T.R. & S.M. Speich. 1984. Survey of marine birds in Puget Sound. Hood Canal and waters east of Whidbey Island. Washington, in summer 1982. West. Birds 15:1-13. Wahl, T.R. . S.M. Speich. D.A. Manuwal. K.V, Hirsch & C. Miller 1981 , Marine bird populations of the Strait of Juan de Fuca. Strait of Georgia, and adjacent waters in 1978 and 1979. DOC/EPA Interagency Energy/ Environment R&D Prog. Rep. EPA 600/7-81-156. U.S. Environmental Protection Agency. Washington. D.C. Wiens. J.A. & J.M. Scott. 1975. Model estimation of energy flow in Oregon coastal seabird populations. Condor 77:439-452. Zar. J.H. 1974. Biostatistical analysis. Prentice-Hall. Englewood Cliffs. NJ. Accepted 12 December 1985 173 174 Ivory Gull (Pagophila eburnea), St Lawrence Island, Alaska, June 1983 Photo by Bruce Maxwell AMERICAN COOT AND BLACK-NECKED STILT ON THE ISLAND OF HAWAII PETER W.C. PATON, Redwood Science Lab, 1700 Bayview Drive, Areata, Califor- nia 95521 J. MICHAEL SCOTT, Condor Research Center, U.S. Fish and Wildlife Service, 2291-A Portola Rd., Ventura, California 93003 (present address: Idaho Cooperative Fisheries and Wildlife Unit, College of Forestry, Range, and Wildlife Science, Univ. of Idaho, Moscow, Idaho 83843) TIMOTHY A. BURR, Hawaii Dept, of Land and Natural Resources, Division of Forestry and Wildlife, Honolulu, Hawaii 96813 (present address: PACNAV- FACENGCO, Code 24-B, Pearl Harbor, Hawaii 96860) Ornithologists studying the wetland avifauna of the island of Hawaii during the late 1800s reported two endemic species (Hawaiian Rail Porzana sand- wichensis and Hawaiian Duck Anas wyuiiliana) , three endemic subspecies (American [Hawaiian] Coot Fulica americana alai, Black-necked [Hawaiian] Stilt Himantopus mexicanus knudseni, and Common [Hawaiian] Moorhen Gallinula chloropus sandvicensis) , and one indigenous species (Black- crowned Night- Heron Nycticorax nycticorax hoactli ) (Wilson and Evans 1890-1899, Rothschild 1893-1900, Henshaw 1902, Perkins 1903), The rail is now extinct. The moorhen, although present on other islands, has been extirpated from Hawaii. The coot, moorhen and duck are classified as en- dangered by the State of Hawaii and the Federal government (USFWS 1983). One other endangered endemic water bird, the stilt, was apparently absent from the island from 1896 to as recently as the early 1960s (Walker 1962, Banko 1979, Paton and Scott 1985). Research is currently being con- ducted on the Hawaiian Duck by the Hawaiian Division of Forestry and Wildlife (HDFW), as information on this species is limited (Jon Giffin pers. comm.) . Surveys of the wetlands of Hawaii conducted over the past 20 years by the HDFW have provided baseline data on the population trends of the coot and stilt (unpubl. data on file, Dept, of Land and Natural Resources, HDFW) . The purpose of this paper is to summarize existing knowledge of these two endemic water birds on the island of Hawaii. STUDY AREA AND METHODS The HDFW (then the Division of Fish and Game) initiated an annual cen- sus of migratory waterfowl in 1950. Native water birds were added to the count in 1958, but it was not until 1963 that all of the primary wetlands used by the coot and stilt on Hawaii were included. These wetlands (Aimakapa, Opaeula, Waiakea, and Lokoaka; Figure 1) have been described by Shallenberger (1977). Ponds on Hawaii are small, less than 11 ha (Arm- strong 1973), with vegetation surrounding the ponds generally short, pro- viding few places for coots and stilts to hide from observers. The HDFW cen- sus is conducted on one day in January, surveying all major wetlands on the island. Eight observers usually conduct the survey, with observers varying from year to year. A summer census, on one day in either late July or early Western Birds 16:175-181. 1985 175 COOT AND STILT ON HAWAII August, was initiated in 1968 to monitor population trends of native water- birds during the critical summer months when water is generally scarce. From 1975 through 1979, Scott regularly surveyed ponds in the Hilo area. Paton censused the major wetlands of the island opportunistically from January 1980 through December 1982. None of these surveys were con- ducted during standardized tidal or weather conditions; nonetheless we believe that the data give a realistic picture of true population figures. Paton did the statistical analysis using MINITAB on the Colorado State University computer system. A priori alpha values of 0.05 were considered significant. Figure 1. Map of the island of Hawaii showing the primary wetlands used by American Coot and Black-necked Stilt. 176 NO. COOTS CENSUSED COOT AND STILT ON HAWAII RESULTS AMERICAN COOT. Information concerning coot population trends prior to 1958 can only be considered speculative. Data reported before the initiation of HDFW censuses were subjective and, therefore, no meaningful inferences could be made to present population levels. The coot was thought to be a common species in the wetlands at lower elevations on Hawaii in the late 1800s, though no population estimates were reported (Henshaw 1902, Perkins 1903). Schwartz and Schwartz (1952) listed the species as “rare” on Hawaii, occurring in a few ponds, reservoirs, and the taro fields of Waipio Valley. These authors did not mention if they visited Aimakapa or Opaeula. Quantitative data collected since 1963 suggest that the coot population has risen recently. In comparing coot winter population figures from 1963 to 1971 with those of 1972 through 1981, one can see that the number of coots has significantly increased in the past decade (Mann-Whitney Test, p = 0.006; Figure 2). The median number of coots counted from 1963 to 1971 was 37.5 (range 20-46), whereas from 1972 through 1981 the median count was 62.5 (range 10-110) . This increase occurred primarily on the west side of the island. The coot population at Aimakapa has increased from 11 birds in 1970 to 165 in September 1984 (HDFW, Pyle 1985). The coot population on the east side of Hawaii has remained relatively small (median = 7.5 birds, range 3-15 during 1982). In 1968, 12 coots were observed at Waiakea Pond, whereas none were seen at Lokoaka Pond (HDFW, summer census data). By 1982, coot habitat use patterns on the east side had changed and the majority of the coots nested and foraged at Lokoaka. From November 1980 through October 1981, no coots were observed at Waiakea Pond during weekly surveys (PWCP pers. obs.). 177 COOT AND STILT ON HAWAII The breeding biology of the coot was recently summarized, but included virtually no data for Hawaii Island because most work was done with this species on Oahu (Byrd et al. 1985). Coots nest at Aimakapa and Opaeula with young observed during all months of the year. However, peak nesting activities appear to occur in July with 10 incubating pairs observed at Aimakapa and 5 incubating pairs at Opaeula (FWCP). Coleman (1978) reported two nesting peaks on Oahu: November-February and June- October. Coot nests have been recorded at Lokoaka, but nesting has not been observed at Waiakea since 1978 (JMS pers. obs.). Four pairs of coots established nests at Lokoaka Pond in 1982, with a minimum of 8 young pro- duced (PWCP pers. obs.). BLACK-NECKED STILT. The status of this species on Hawaii Island remains uncertain. There are no fossils known of this species from Hawaii Island (Olson and James 1982). S.B. Wilson collected 1 adult female stilt in June 1896 labelled “Hawaii, H.I.” (Carnegie Museum 55460), which is most likely from Hawaii Island (Banko 1979). We could find no other records of stilt between 1896 and 1961 on the island. No other ornithologist doing work in the late 1800s recorded stilts on Hawaii (Rothschild 1893-1900, Henshaw 1902, Perkins 1903) . It is not known if any of these men visited Opaeula, but Perkins (1893) definitely visited Aimakapa to collect birds. Munro (1944) specifically stated that “there seems to be no record of it [stilt] from Hawaii.” Figure 3. Black-necked Stilt winter HDFW census results from 1963 to 1981. 178 COOT AND STILT ON HAWAII The first documented record we could find of stilts on Hawaii was of two birds seen at Aimakapa in August 1961 (Walker 1962). Since 1963, the stilt population has remained relatively stable (Figure 3) . A comparison of the island’s stilt population from 1963 to 1971 versus 1972 to 1981 yielded no significant difference between the two periods (Mann- Whitney Test, p = 0.103). The median count for 1963 to 1971 was 27.5 (range 11-36), whereas from 1972 to 1981 the median count was 20 (range 11-26; HDFW). The highest stilt count on Hawaii was in January 1968, when 36 birds were recorded, but 35 stilts were counted as recently as 17 October 1982 (PWCP pers. obs.). Stilts nested at Aimakapa and Opaeula during the 1960s and 1970s (Eugene Kridler and Robert Shallenberger pers. comm.). Five stilt chicks were observed at Aimakapa in May 1982 and one chick at Opaeula on 25 September 1982 (PWCP pers. obs.). On Oahu, the stilt breeding season usually extends from March through August but is concentrated in May and June (Coleman 1981). We did find a difference between summer and winter HDFW stilt censuses (Mann- Whitney Test, p = 0.04), although the biological implications of this observation are unclear. Surprisingly, the winter counts (median = 24, range = 16-36) were greater than the summer counts (me- dian = 19, range = 15-27). Because stilts are thought to breed primarily prior to the summer census, we would have expected to see higher counts in July- August. The higher winter counts may be the result of post-breeding movements between islands; however, these results warrant further study. There is only one reported record of a stilt on the east side of Hawaii. One bird was observed flying over Lokoaka on 11 April 1981. A sighting later the same week in the Mountain View area was probably the same bird. Our data suggest intra-island movements of stilts, primarily between Opaeula and Aimakapa. Censuses on 19 July, 26 July and 16 August 1981 showed the same number of birds, but in different proportions, at Aimakapa and Opaeula (16:14, 18:12 and 22:8, respectively). Inter-island movements of stilts have been documented between Kauai and Oahu, and Maui and Oahu (E. Kridler and R. Coleman pers. comm.). Intra-island movements of banded birds have also been documented (E. Kridler and R. Coleman pers. comm.) . DISCUSSION Increases in the coot population on Hawaii are probably due to changes in human use of the ponds on the west side of the island. Up to the early 1960s, Aimakapa was used by Hawaiians for the production of fish (E. Kridler pers. comm.). The continued disturbance caused by the maintenance of the pond’s stone walls and the use of throw nets to capture fish probably limited the number of water birds using the pond. Since the early 1960s, the primary disturbance at Aimakapa is people using the beach on the west side of the pond. Water birds generally utilize only the east side of the pond now, except during crepuscular hours when human disturbance of the area is at a minimum (PWCP pers. obs.). Opaeula was used at one time by Hawaiians as a fish production pond, but now human disturbance of the area is sporadic. 179 COOT AND STILT ON HAWAII Reasons for the avoidance of Waiakea Pond by coots are difficult to deter- mine, though some observations suggest that the encroachment of grass into the shallower regions of the pond may inhibit coot utilization of the area. Throughout 1981 Para Grass ( Brachiaria mutica ) spread rapidly over the edges of Waiakea, extending up to 6 m in areas where the water was up to 1 m deep. Also, during this period the mouth of the Wailoa River, which flows into Waiakea, was completely covered by this exotic grass (PWCP pers. obs.). Para Grass was controlled up to 1979 with herbicides by the State Department of Parks and Recreation (George Kanemota pers. comm.). The Para Grass was dredged from the edges of the pond in June 1982 and up to 5 coots were observed foraging at Waiakea from August through October 1982 (PWCP pers. obs.), indicating that lack of foraging locations at Waiakea was limiting coot use of the pond. The absence of stilts on the east side of the island may be due to the lack of suitable foraging sites. Both Lokoaka and Waiakea have steep banks and are too deep (>1 m) to allow stilts to walk on the bottom. Aimakapa and Opaeula on the other hand are generally shallow (<20 cm) and Opaeula in particular has several large shallow mudflats ideal for stilt foraging. Aimakapa and Opaeula have been designated by the Hawaiian Waterbird Recovery Plan as 2 of 17 essential water bird habitats in the Hawaiian Islands. Present plans propose federal acquisition of both ponds (Hawaiian Waterbird Recovery Team 1977). Aimakapa and Opaeula are presently under private ownership and future preservation of these two wetlands is uncertain. Loss of this habitat would mean the probable demise of stilts from the island and cause a significant reduction in coot numbers on Hawaii. In addition to being the primary nesting and foraging areas for over 95% of the island’s stilts and 90% of the coots, over 100 migratory waterfowl regularly use these areas during the winter months (Paton and Scott 1985). With the exception of data on population trends of these two species, their ecology has been little studied on Hawaii Island, in part because the Hawaii Island population represents only 3% of the total Hawaiian population for both the coot and stilt (Shallenberger 1977) . Continued development of the lowlands of the Hawaiian Islands can only result in reduced numbers of Hawaii’s endemic w»ater birds. The importance of a specific wetland may not always be evident because the factors governing the utilization of an area by birds are often not fully understood. The only known breeding records of migratory waterfowl in the Hawaiian Islands occurred at Aimakapa, when Blue- winged Teal ( Anas discors) nested at Aimakapa in 1982 and 1983 (Paton et al. 1984), yet Blue-winged Teal are an uncommon migrant to the island. One has to keep in mind that on Hawaii, where wetlands are limited, each wetland can have biological importance. LITERATURE CITED Armstrong, R.H., ed. 1973. Atlas of Hawaii. Univ. Hawaii Press, Honolulu. Banko, W.E. 1979. Endemic Hawaiian birds specimens in museum collections. CPSU/UH Avian History Report 2. Univ. Hawaii Manoa, Honolulu. Byrd, G.V., R.A. Coleman, R.J. Shallenberger & C.A. Aruma. 1985. Notes on the breeding biology of the Hawaiian race of the American Coot. Elepaio 45:57-63. 180 COOT AND STILT ON HAWAII Coleman, R.A. 1978. Coots prosper at Kakahaia refuge. Elepaio 38:130. Coleman, R.A. 1981. The reproductive biology of the Hawaiian subspecies of the Black-necked Stilt, Himantopus mexicartus knudseni. PhD. diss., Pennsylvania State Univ., University Park, PA. Hawaiian Waterbird Recovery Team. 1977. Hawaiian Waterbird Recovery Plan . U.S. Fish and Wildlife Service, Washington, D.C. Henshaw, H,H, 1902. Birds of the Hawaiian Islands. Thos G. Thrum, Honolulu. Munro, G.C. 1944. Birds of Hawaii. Charles E. Tuttle Co., Inc. Rutland, VT. Olson, S.L. & H.F. James. 1982. Prodromus of the fossil avifauna of the Hawaiian Islands. Smithsonian Contr. Biol. 365. Smithsonian Instit. Press. Washington, D.C. Paton, P.W.C. & J.M. Scott. 1985. Water birds of Hawaii Island. Elepaio 45:69-76. Paton, P.W.C. , A. Taylor & P.R. Ashman. 1984. Blue-winged Teal nesting in Hawaii. Condor 86:219. Perkins, R.C.L. 1893. Notes on collecting in Kona, Hawaii. Ibis 1893:110-114. Perkins, R.C.L. 1903. Vertebrata (Aves). In Fauna Hawaiiensis. 1(4) :368-465. Cambridge Univ. Press, London. Pyle, R.L. 1985. Hawaiian Islands region. Am. Birds 39:106. Rothschild, W. 1893-1900. The avifauna of Laysan and the neighbor islands. R.H. Porter, London. Schwartz, C.H. & E.R. Schwartz. 1952. The Hawaiian Coot. Auk 69:446-449. Shallenberger, R. 1977. An ornithological survey of Hawaiian wetlands. U.S. Army, Engineer District, Honolulu. United States Fish & Wildlife Service (USFWS). 1983. Republication of the lists of endangered and threatened species and corrections of technical errors in final rules. Fed. Reg. 50(99) :33767-33781. Walker, R.L. 1962. Field notes from the island of Hawaii. Elepaio 22:7. Wilson, S.B. & A.H. Evans. 1890-1899. Aves Hawaiiensis: the birds of the Sandwich Islands. R.H. Porter, London. Accepted 11 December 1985 181 New From Artemisia Press The Distribution of the Birds of California JOSEPH GRINNELL and ALDEN H. MILLER Published in 1944 by the Cooper Ornithological Society, Grinnell and Miller’s The Distribution of the Birds of California remains the definitive benchmark on California’s avifauna. It summarizes a wealth of information on the seasonal status, abundance and geographic range of the 644 species and subspecies then recorded in the state. Its terse yet detailed descriptions of habitat and habitat re- quirements have yet to be bettered. It is an indispensable reference for anyone seriously interested in California’s birds. This Artemisia Press edition is an exact reproduction of the original text. It also includes an interview with Dr. Frank A. Pitelka on the book’s genesis and significance. New appendices update nomenclature and list recent publications on California bird distribution. 616 pages; 6” x 9”; 57 distribution maps; 1 black-and-white illustra- tion. $18.00 paperback, $25.00 hardbound including shipping and handling. ORDERING INFORMA TION To order, please send check or money order payable to Artemisia Press ( price includes shipping and handling; California residents please add 6% sales tax). We also accept orders by phone. If you would like your order shipped first class, please add $3.50 per book; otherwise allow three weeks for delivery. We wholesale to book dealers. ARTEMISIA PRESS, P.O. Box 119, Lee Vining, CA 93541 (619) 647-6496 NOTES RECENT ALTITUDINAL RANGE EXPANSION BY THE BROWN-HEADED COWBIRD IN COLORADO LADISLAV R. HANKA, Department of Zoology and Entomology, Colorado State University, Fort Collins, Colorado 80523 (present address: 1146 Douglas, Kalamazoo, Michigan 49007) During a 2- year study of brood parasitism by the Brown- headed Cowbird (Molothrus ater) in 1977 and 1978 in Colorado, 1 noted substantial differences in the cowbirds’ range from that described in the earlier literature. Although the Brown-headed Cowbird is among the bird species described by the first naturalists in Colorado (Bailey arid Niedrach 1965, Marsh 1968), virtually all observations of cowbirds at high altitudes are recent, Bailey and Niedrach (1965) described the Brown -headed Cowbird as a resident of the foothills, ranging up to 2134 m. Davis (1969) described cowbirds as common at lower elevations in western Colorado. Only Cooke (1897) mentioned cowbirds breeding up to 2440 m, but he considered them to be confined primarily to lower elevations. Warren (1980) was cited by Sclater (1912) as having observed cowbirds in Routt and Grand counties. However, Warren’s expedition was for the purpose of mammal collecting and no loca- tions of bird sightings were published. Sclater (1912) also considered the Brown- headed Cowbird to be a bird of the plains and foothills. 1 have found Brown- headed Cowbirds to be as common in the mountain parks and river valleys as in the foothills and have frequently observed cowbirds up to 2895 m. I have seen individual cowbirds at Antero Reservoir, Park Co. (2725 m); 14 at Jeffer- son, Park Co. (2895 m); 15 at Malta, Lake Co. (2890 m); 25 at Gould, Jackson Co. (2712 m): flocks in excess of 25 up to 2500 m in the Laramie River valley, Larimer Co.; small flocks (3-8) up to 2650 m in upper Cherokee Park, Larimer Co.; and 20-40 at various times at Lake John Annex, Park Co. (2455 m). All sightings were from late May and June when the birds would be expected to be breeding. The highest elevation I have found cowbird eggs has been 2475 m at South Delaney Buttes Reservoir in North Park, Park Co. Brewer’s Blackbirds ( Euphagus cpanocephalus) are commonly parasitized at Lake John Annex in North Park. Of 45 nests examined, 18 (40%) contained a total of 66 cowbird eggs Three nests con- tained four cowbird eggs each and one nest contained six cowbird eggs in addition to three Brewer’s Blackbird eggs. Keeler-Wolf et al. (1972) reported finding a cowbird egg in a Yellow Warbler ( Dendroica petechia) nest near Crested Butte, Gunnison Co. (2895 m), and considered the Brown-headed Cowbird to be common in the area. Thus, the Brown- headed Cowbird is presently a common breeding bird at substan- tially higher elevations than generally reported by earlier naturalists. Unless it was generally overlooked, the Brown- headed Cowbird has recently expanded its numbers and range in the mountain parks and river valleys of Colorado. The Brewer’s Blackbird is clearly a major host to the Brown -headed Cowbird at high elevations. However, unlike the cowbird, the Brewer’s Blackbird has been an abundant breeding bird up to 3050 m from at least the late 19th century on (Cooke 1897. Sclater 1912). Therefore, it is unlikely that the spread of the Brown-headed Cowbird is correlated with the spread of this host species. Range expansion eastward by the Brown -headed Cowbird has been largely at- tributed to clearing of the forests and increased agriculture (Friedmann 1963, Mayfield 1965) . The mountain parks and upper river valleys in Colorado are heavily grazed by Western Birds 16:183-184, 1985 183 NOTES cattle, and the altitudinal range expansion of the Brown-headed Cowbird in Colorado may be attributable to habitat alteration. A similar expansion of range in the Sierra Nevada of California was discussed by Rothstein et al. (1980) and Verner et al. (1983). I thank Paul Baldwin, C. Richard Tracy and Ronald Ryder for reading the manuscript and offering criticisms. LITERATURE CITED Bailey, A.M. & R.J. Niedrach. 1965. Birds of Colorado. Denver Mus. Nat. Hist., Denver. Cooke, W.W. 1897. The birds of Colorado. State Agric. Coll. Bull. 37, Tech. Ser. 2, 224 p. Davis, W.A. 1969. Birds in western Colorado. Colorado Field Ornithol., Boulder. Friedmann, H. 1963. Host relations of the parasitic cowbirds. U.S. Natl. Mus. Bull. 233. Marsh, T.G. 1968. Chronological list of first records of birds seen in Colorado prior to settlement. Colorado Field Ornithol. 3:17. Mayfield, H. 1965. The Brown-headed Cowbird with old and new hosts. Living Bird 4:13-19. Keeler- Wolf, T., V. Keeler- Wolf & W.A. Calder. 1972. Bird fauna of the vicinity of the Rocky Mountain Biological Laboratory. Colorado Field Ornithol. 15:22-25. Rothstein, S,L, J. Verner & E. Stevens. 1980. Range expansion and diurnal changes in dispersion of the Brown-headed Cowbird in the Sierra Nevada. Auk 97:253-267. Sclater, W.L. 1912. A history of the birds of Colorado. Witherby & Co., London. Verner, J. & L.V. Ritter, 1983. Current status of the Brown -headed Cowbird in the Sierra National Forest. Auk 100:355-368. Warren, E.R. 1908. North-western Colorado bird notes. Condor 10:18-26. Accepted 16 April 1985 184 NOTES UNUSUAL NEST SITE FOR GREATER SANDHILL CRANES IN COLORADO KEVIN L. ELLIS, Colorado Division of Wildlife, 711 Independent Avenue, Grand Junction, Colorado 81501 (present address: Colorado Division of Wildlife, 151 E. 16th Street, Durango, Colorado 81301) JAMES HASKINS, P.O. Box 828, Hayden, Colorado 81639 In Colorado, the Greater Sandhill Crane (Grus canadensis tabida ) historically nested in high mountain parks (to 2896 m) over much of the western portion of the state (Sclater 1912, Bailey and Niedrach 1965). Currently it nests only in Jackson and Routt counties (Walkinshaw 1973, Bieniasz 1978, Ellis and Haskins 1982) in areas of open parkland with willow ( Salix spp.) lined drainages and sagebrush (Artemisia spp.) covered ridges. These parklands are surrounded by Quaking Aspen ( Populus tremuloides ) with mixed Lodgepole Pine ( Pinus contorta ) and Subalpine Fir ( Abies lasiocarpa) . All previous confirmed Greater Sandhill Crane nests (n - 104) in Col- orado have been in water or very closely associated with water (Ellis and Haskins 1982). This note describes a nest located during 1982 in habitat not previously reported for Greater Sandhill Cranes in Colorado. On 18 June 1982 we received a report of a crane nest containing one egg near a dry-land wheat field 15 km northwest of Steamboat Springs (Routt County). A search on 24 June resulted in the discovery of a pair of adult Greater Sandhill Cranes. As we approached, the pair sounded alarm calls (Voss 1976), flushed, and circled overhead for approximately 1 minute before landing on a hillside 0.3 km away where they con- tinued to call. A search in the area from which they flushed revealed a typically con- structed ground nest of small diameter twigs. On top of the nest was an inner shell membrane and egg shell fragments. The parental behavior of the adults and the evidence found on the nest indicated that the egg had hatched successfully. Our search for the chick was unsuccessful. After we left the immediate area of the nest one of the adults returned; the other remained on the hillside, calling, until we departed. The nest was placed on a hillside dominated by sagebrush, Gambel’s Oak (Quercus gambelii), mule’s ear (Wyethia amplexicaulis) , and mixed grasses. A dry-land, fallow wheat field was located approximately 75 m east and a moderately used county road was 200 m east. No open water was visible from the nest although the presence of a small group of sedges ( Carex ; approximately 250 m 2 ) just east of the county road sug- gests it may have been a seepage area earlier in the year. The nearest available water at the time of nest discovery consisted of a stock pond approximately 0.8 km away. On 25 July we returned to band the chick. The area was very dry and most of the ground vegetation was dead. No cranes were seen during a thorough search. It is not known whether the chick perished or was taken to more suitable habitat by the adults. The affinity of Greater Sandhill Cranes for water when choosing a nest site has been well documented (Walkinshaw 1973, Littlefield and Ryder 1968, Drewien 1974). In Oregon, Littlefield and Ryder (1968) found that only 2 of 122 nests were not in or very near water; both were approximately 200 m distant. Greater Sandhill Cranes in Idaho, however, show a stronger tendency to nest on dry land (Drewien 1974) . Mean distance from water for the 150 dry-land nests observed by Drewien was 4.6 m (mode = 0.3 m). The aforementioned seepage may have provided the water element that seems to be essential to Greater Sandhill Crane nesting territories at the time of nest initiation. Our observations were made while under the employ of the Colorado Division of Wildlife, federal aid project SE-5-1. We thank project coordinator Tom Lytle for logistic support. Ronald Ryder. C.D. Littlefield, Scott Derrickson. Joseph R. Murphy. Clayton M. White and Robert J. Meese reviewed earlier drafts of the manuscript. Western Birds 16:185-186, 1985 185 NOTES LITERATURE CITED Bailey, A.M. & R,J. Niedrach. 1965. Birds of Colorado. Vol. 1. Denver Mus. Nat. Hist., Denver. Bieniasz, K.A. 1978. The Greater Sandhill Crane in Routt County, Colorado. Pp. 197-203 in J.C. Lewis, ed., Proceedings 1978 crane workshop. Colorado State Univ. Print. Serv,, Ft. Collins. Drewien, R.C. 1974. Ecology of Rocky Mountain Greater Sandhill Cranes. Ph.D. dissertation. Univ. Idaho, Moscow. Ellis, K.L. & J. Haskins. 1982. Whooping Crane and Greater Sandhill Crane pop- ulation and habitat monitoring. Colorado Div. Wildl., Job Perfor. Rep., SE-5-1. Littlefield, C D. & R.A. Ryder. 1968. Breeding biology of the Greater Sandhill Crane on Malheur National Wildlife Refuge, Oregon. Trans. 33rd North Am. Wildl. Conf.:444-454. Sclater, W.L. 1912. Birds of Colorado. Witherby & Co., London. Voss, K.S. 1976. Behavior of the Greater Sandhill Crane. M.S. thesis, Univ. Wisconsin, Madison. Walkinshaw, L. 1973. Cranes of the world. Winchester Press, New York. Accepted 27 October 1984 186 NOTES PARTIAL ALBINISM IN A M ELAN (STIC MEW GULL JON WINTER, 1158 Humboldt St. #7, Santa Rosa, California 95404 On 18 February 1979, at Moss Landing, Monterey Co., California, I observed for 5 minutes and photographed (Figure 1) a predominately melanistic gull that had pure white feathering scattered over the body and wings. I identified the bird as a sub-adult Mew Gull (Larus canus) on the basis of size, head and bill shape, and voice. Com- pared to nearby California Gulls (L. californicus ) , it was distinctly smaller and had a more rounded forehead and smaller bill. The high pitched call characteristic of this species was heard two or three times. The leg color was pink, which is typical of Mew Gulls in their first year. 1 did not note the bill color. The predominate color of the body and wings was a deep chocolate brown close to the “blackish brown” of Villalobos (1962) and only slightly darker than the color of a first-year Heermann’s Gull (L, heermanni). This color appeared to be evenly distributed over the wings and body, with no evidence of counter-shading. The white feathering was confined to the crown, nape, sides of the head, scapulars, right flank, the outer five or six primaries of the left wing, and the upper primary coverts of the right wing. Gross (1965b) reported only two cases of melanism in North American gulls, one each in the Herring Gull (L. argentatus) and the Laughing Gull (L. atricilla). Of 1847 cases of partial or complete albinism in North America, Gross (1965a) reported 33 Jll- Figure 1 . A melanistic Mew Gull (Larus canus) with partial albino feathering at Moss Landing, Monterey Co., California on 18 February 1979. Western Birds 16:187-188. 1985 Photos by Jon Winter 187 NOTES (1.8%) in the Laridae, involving 10 species. He did not list the cases by species. Sage (1962) reported albinism in L. c. canus and seven other gulls found in the British Isles and melanism in the Lesser Black-backed Gull (L. fuscus) , Herring Gull and Common Black-headed Gull (L. ridibundus ) . The occurrence of albinism and melanism in a single individual appears to be an ex- ceptionally rare phenomenon, I was able to find only one case in a gull. Harrison and Harrison (1962) reported a Black-headed Gull from the British Isles that had entirely white primaries but otherwise normally pigmented feathers; the melanism was con- fined to patches on the tarsi, toes, webs and nails. Sage (1962) noted the combination of albinism and melanism in a Eurasian Curlew (Numenrus arquata) and a Blue Tit (Parus caeruleus) in the British Isles. Harrison (1963) warned that many cases of so-called melanism have turned out to be “industrial” discoloration. If the Moss Landing bird had been stained, I would have expected the dark plumage to be less uniform and the unpigmented feathers to show some evidence of discoloration. This was not the case. Any explanation for the unusual plumage in this gull is tenuous at best. Sage (1962) indicated that abnormal melanism and partial albinism can result from a number of dif- ferent (including nongenetic) phenomena. Partial albinism has been linked to changes in diet (Rollin 1953, 1959), injury (Hutt 1949), disease (Brimley 1944) and possibly shock and age (Sage 1962) . Abnormal melanism has been attributed to the dietary deficiency of vitamin D in poultry (Decker and McGinnis 1947). The Mew Gull at Moss Landing appeared to be healthy, and no unusual behavior was noted. This note is Contribution 218 of Point Reyes Bird Observatory. LITERATURE CITED Brimley, C.S. 1944. Albinism sometimes due to injuries. Chat 8:11. Decker, A. & J. McGinnis 1947. Black pigmentation in feathers of Buff Orpington chicks caused by vitamin D deficiency. Proc. Soc. Exp. Biol. 66:224-228. Gross, A.O. 1965a. Melanism in North American birds. Bird Banding 36:240-242. Gross, A.O. 1965b. The incidence of albinism in North American birds. Bird Banding 36:67-71. Harrison, C.J.O. 1963. ‘Industrial’ discoloration of House Sparrows and other birds. British Birds 56:296-297. Harrison, J.M. & J.G. Harrison. 1962. A Black- headed Gull showing both albinism and melanism. British Birds 55:435-436. Hutt, F.B. 1949. Genetics of the fowl. McGraw-Hill, New York, Rollin, N. 1953. A note on abnormally marked Song Thrushes and Blackbirds. Trans. Nat., Hist. Soc. Northumberland & Durham 10:183-184. Rollin, N. 1959. White plumage in Blackbirds. Bull. British Ornithol. Club 79:92-96. Sage, B.L. 1962, Albinism and melanism in birds, British Birds 55:201-225. Villalobos, J. 1962. Color standard. In R.S. Palmer, ed. Handbook of North American birds, Vol. 1. Yale Univ. Press, New Haven & London. Accepted 15 Nouember 1985 188 IDENTIFICATION NOTES m The Identification Paper Committee continues to encourage the submission of brief notes on yet-to-be-resolved identification problems. The following note on the calls of two very similar Empidonax flycatchers is an example of such a note. It is not intended to be the final word, but will encourage, we hope, further investigation. CALLS OF ALDER AND WILLOW FLYCATCHERS Until fairly recently, most observers did not attempt to separate Alder ( Empidonax alnorum) and Willow (£. traillii ) flycatchers in the field except by song and, indirectly, by breeding range and habitat (not safe in many areas). The idea that these two species, and most Empids in general, are readily identifiable only on the basis of song and breeding habitat has been instilled by many of the early breed of field guides. The result has been that many observers do not attempt identification of migrating Em- pidonax flycatchers. But many individuals in this group call during migration, as well as on the breeding and wintering grounds, and these calls are very useful in identifying many of them to species. Many silent Empids, if followed long enough, will give a call note (or rarely, in a few species such as Willow, a song) at some point! The typical call notes of Alder and Willow flycatchers are distinctly different, and probably provide, in addition to song, the best means of identifying the two in the field. Willow’s typical call is a liquid “whit,” softer in tone than the more emphatic, sharp “whit” of the typical Least Flycatcher (E. minimus). Willow Flycatchers are fre- quently heard calling in migration. The typical call of the Alder Flycatcher is a sharp note, variously transcribed “pip,” “peek,” or “bic.” The quality of this call is quite dif- ferent from that of a Willow, and has been likened to the call of Hammond’s Fly- catcher (E. hammondii) , Pygmy Nuthatch (Sitta pygmaea), or, vaguely, Long-billed Dowitcher ( Limnodromus scolopaceus ) . Certain other, less commonly heard calls of Alder and Willow flycatchers may also be useful for identification; here is a fruitful area for further study. Although most observers will be understandably reluctant to report extralimital sightings of either species solely on the basis of calls, awareness of these differences can allow observers to focus their attention on the odd-sounding individuals. In- creased attention to identification of these two species on migration would certainly go a long way towards a better understanding of their relative status in different parts of the continent. PAUL LEHMAN, P.O. Box 1061, Goleta, California 93116 PLUMAGE WEAR IN VIREO BELLI I PHILIP UNITT, 3411 Felton Street, San Diego, California 92104 In this note I respond to and expand on some of the ideas presented by Stallcup (1984) in his “identification quiz” on Bell’s Vireo. The bird depicted in the quiz was photographed at San Bias, Nayarit, in December 1975. The published black-and- white print is a reproduction of an original color slide, which Bruce Webb and Tim Manolis kindly loaned me. The written description in the quiz, however, is of a bird captured in San Diego County, California, as Stallcup (pers. comm.) has pointed out. Stallcup’s description, “in life, this bird was white below and gray above with scarcely a Western Birds 16:189-190, 1985 189 NOTES trace of green or yellow,” implied that a bird answering the description of V.b . pusillus had been photographed at San Bias, since the discussion did not mention the prove- nance of the bird on which the written description was based. This erroneous impres- sion merits correcting because the published winter range of pusillus is confined to southern Baja California (Friedmann et al, 1957, AOU 1957). The bird photographed in San Bias, to judge from the original color slide, was most likely not pusillus, since it shows some contrast between a plain gray head and a slightly olive-tinged back. Any further speculation on its subspecific identity is unwarranted; identification of Bell’s Vireo races cannot be made conclusively on the basis of photographs, since light and film conditions are unknown variables. As with most subspecies, such identifications must be made through comparison with preserved specimens. Vireo bellii consists of four subspecies: pusillus, breeding in California and north- western Baja California (see Goldwasser et al. 1980 and Wilbur 1980 for details of current range), arizonae, breeding from the Colorado River east through Arizona and south through Sonora, medius, breeding from western Texas south to northern Durango and eastern Coahuila, and nominate bellii, breeding from eastern Colorado, eastern Texas, and Tamaulipas east to the Mississippi River region (Ridgway 1904, AOU 1957) . As Stallcup mentions, the eastern races are brighter green and yellow than the western. More specifically, the four races represent a gradation: each subspecies is more brightly colored than its neighbor to the west. Plumage wear and fading, however, markedly change the birds’ appearance; they convert yellow-green birds into grayer ones. To identify properly specimens of Bell’s Vireo, one must com- pare birds collected at the same season. Faded summer specimens of arizonae become as gray as fresh fall pusillus. (Bell's Vireo has the molt schedule common among North American passerines: a single complete annual molt, which takes place after nesting but within the breeding range.) A medius collected on 8 May looks much like an arizonae collected on 25 January; both specimens are in the San Diego Natural History Museum and were identified by Allan R. Phillips. This January arizonae has a conspicuously greenish back and yellowish flanks that distinguish it easily from even the freshest (late August) specimens of pusillus. The difference in fresh plumage be- tween pusillus and this specimen of arizonae is enough to surprise a Californian like myself who is familiar only with pale gray, faded, summer pusillus. I suspect that many of the fall sight records of “eastern” Bell’s Vireos in California are based on fresh arizonae. I thank Rich Stallcup and Tim Manolis for their review of an earlier version of this note and for correcting the confusion in the identification quiz. I thank Allan R. Phillips for identifying the January specimen of arizonae that turned my attention to the pro- blem of plumage wear in Vireo bellii. LITERATURE CITED American Ornithologists’ Union. 1957. Check-list of North American birds. 5th ed. Am. Ornithol. Union, Baltimore, MD. Friedmann, H., L. Griscom & R.T. Moore. 1957. Distributional check-list of the birds of Mexico, part 2. Pac. Coast Avifauna 33. Goldwasser, S,, D. Gaines & S.R. Wilbur. 1980. The Least Bell’s Vireo in California: a de facto endangered race. Am. Birds 34:742-745. Ridgway, R. 1904. Birds of North and Middle America. U.S. Natl. Mus. Bull. 50, part 3. Stallcup, R. 1984. Identification quiz. West. Birds 15:95-96. Wilbur, S.R. 1980. The Least Bell’s Vireo in Baja California, Mexico. West. Birds 11:129-133. 190 Accepted 23 August 1985 INDEX, WESTERN BIRDS, VOLUME 16, 1985 Compiled by Mildred Comar Accipiter cooperii, 124 striatus , 14, 15, 126, 143 Actitis macularia, 65, 66 Aegolius acadicus, 5, 14, 15, 18, 19, 25-28 Aethia pusilla, 29 Agelaius phoeniceus, 65, 68 Aimophila cassinii, 41, 51 Alauda aruensis, 37 Albatross, Black-browed, 107 Black-footed, 82, 83 Laysan, 33, 42, 83, 86, 90, 107 Aiectoris chukar, 64, 66, 121 Ammodramus bairdii, 41 caudacutus, 42, 117 leconteii, 42 Amphispiza belli, 12 bilineata, 51. 68, 69 Anas americana, 65 discors, 180 cyanoptera, 65 formosa, 109 platyrhynchos, 65 rubripes, 45 strepera, 65 Anhinga, 45 Anhinga anhinga, 45 Anthus cervinus, 38, 40, 114 spinoletta, 16 spragueii, 38, 44 Aquila chrysaetos, 64, 66, 124, 128 Archilochus alexaridri, 66 Arenaria interpre s, 71 Asio flammeus, 126 otus, 25-28 Athene cunicularia, 124 Auklet, Least, 29 Aythya fuligula, 34, 109 Barn-Owl, Common, 25-28, 126 Bayer, Range D., Nearshore flights of seabirds past Yaquina Estuary, Oregon, during the 1982 and 1983 summers, 169-173 Bernstein, Chuck, The Joys of Birding (review), 104 Binford, Laurence C., Seventh report of the California Bird Records Commit- tee, 29-48 Blackbird, Brewer’s, 68. 183 Red-winged. 65, 68 Yellow-headed, 65,68 Bluebird, Eastern, 146, 162, 163, 166 Mountain, 67, 146, 161-168 Western, 146 Booby, Brown, 33, 108 Masked, 31, 85, 87, 90 Bowers, Richard K., Jr., and John B. Dunning, Jr., Predator avoidance through burrow use by Cassin’s and Black-throated sparrows, 51 Brachyramphus brevirostris, 29, 36 Bubo uirginianus, 25-28, 66, 126 Bubulcus ibis, 87 Bunting, Indio, 29 Lazuli, 65, 68, 69 Painted, 41, 1 17 Burr, T., see Paton, P. Bushtit, 50, 67 Buteo albicaudatus, 118 albonotatus, 34, 110 jamaicensis, 57, 64, 124-128 lagopus, 124, 126, 128 lineatus, 124, 126 regalis, 124, 126 swamsonf, 126 Calidris acuminata, 35 ferruginea, 35 fuscicollis, 35 pusilla, 35, 118 ruficollis, 35, 110 Callipepla californica, 64, 66 Calonectris leucomelas, 108 Cardeltina rubrifrons, 116 Cardinal, Northern, 117, 121 Cardinalis cardinalis, 117, 121 Carduelis lawrencei, 13, 18 pinus, 14, 15 psaltria, 13, 18 tristis, 65, 68 Carpodacus cassinii, 13, 16, 19, 68 mexicanus, 13, 68 purpureus, 12, 13, 15, 18, 19 Catbird, Gray, 38, 114 Cathartes aura, 126 Catharus fuscescens, 44, 114, 120 guttatus, 14, 15 ustulatus , 14, 15 Catherpes mexicanus, 67 Centrocercus urophasianus, 64, 66 Cepphus columba, 169, 171, 172 Certhia americana, 14, 15 Chaetura uauxi, 65, 66 Western Birds 16:191-198, 1985 191 Chamaea fasciata fasciata, 15 Charadrius melodus , 34, 42 mongolus, 110 vociferus, 66, 69 wilsonia, 42 Chat, Yellow-breasted, 65, 68 Chen canagica, 34 Chickadee, Chestnut-backed, 14, 15, 16 Mountain, 14, 15, 64, 67 Chondestes grammacus , 64, 68 Chordeiles minor, 66 Chukar, 64, 66, 121 Cicero, C., see Johnson, N.K. Cinclus mexicanus, 8, 14, 15 Circus cyaneus, 124, 126 Coccothraustes uespertinus, 63, 68 Coccyzus erythropthalmus, 37, 112 Colaptes auratus, 66 Columba liuia, 64, 66 Columbina talpacoti, 45 Contopus borealis, 5, 15, 18 pertinax, 112 sordidulus, 5, 15, 16, 18, 19, 65, 67, 69 uirens, 112, 113, 120 Coot, American, 66 American (Hawaiian), 175-181 Coragyps atratus, 31 Cormorant, Brandt’s, 87, 169, 171 Double-crested, 109 Olivaceous, 34, 108 Pelagic, 169,171 Coruus brachyrhynchos, 67 corax, 64, 67 Cowbird, Brown-headed, 68, 183-184 Crane, Greater Sandhill, 185-186 Lesser Sandhill, 151 Creeper, Brown, 14, 15 Crow, American, 67 Cuckoo, Black-billed, 37, 112 Curiew, Eurasian, 188 Cyanocitta cristata, 38 stelleri, 8, 15, 18 Cygnus buccinator, 34 Cynanthus latirostris, 37, 112, 119 Daption capense, 42 Dendragapus obscurus, 64, 66 Dendrocygna autumnalis, 121 Dendroica castanea, 158 cerulea, 116 coronata, 10, 14, 15, 16, 19 dominica, 39, 95-97, 116 graciae, 39 magnolia, 159 nigrescens, 11, 18, 64, 67 petechia, 64, 67, 185 pinus, 39, 120 striata, 159 tigrina, 158 uirens , 158 DeSante, David F., Ned K. Johnson, Ron LeValley and Robert P. Henderson, Occurrence and identification of the Yellow-bellied Flycatcher on Southeast Farallon Island, California, 153-160 Dickcissel, 123 Diomedea immutabilis, 33, 42, 81-83, 86, 90,107 melanophris, 107 nigripes, 82, 83 Dipper, American 8, 14, 15 Dove, Mourning, 66, 98 Rock, 64, 66 DuBowy, Paul J. and Steven W. Moore, Weather-related mortality in swallows in the Sacramento Valley of California, 49-50 Duck, American Black, 45 Tufted, 34, 109 Dumetella carolinensis, 38, 114 Dunning, J.B., Jr., see Bowers, R. Eagle, Bald, 124, 126 Golden, 64, 66, 124, 128 Egret, Cattle, 87 Eider, King, 34, 109 Steller’s, 105, 110 Elanoides forficatus, 42 Elanus caeruleus, 57-61, 124, 126 Elliott, Bruce, Changes in distribution of owl species subsequent to habitat alteration by fire, 25-28 Ellis, Kevin and James Haskins, Unusual nest site for Greater Sandhill Cranes in Colorado, 185-186 Emlen, John T. and Ruth R, Ogden, Nesting doves and thrashers share close quarters, 98 Empidonax alnorum, 189 difficilis, 6, 153-159 flauiuentris, 153-160 hammondii, 192 minimus, 37, 113, 153, 159, 192 oberholseri, 5, 14, 15, 18, 19 trailii, 66, 189 192 uirescens, 29, 43 wrightii. 6, 18, 19, 20, 67 Eudocimus albus, 120 Euphagus cyanocephaius, 68, 183 Falco columbarius, 124 mexicanus, 64, 66, 124, 126, 128 peregrin us, 126 rusticolus, 34 sparverius, 66, 124, 126-128 Falcon, Peregrine, 126 Prairie, 64, 66. 124, 126, 128 Finch, Cassin’s, 13, 16, 19, 68 House, 13, 68 Purple, 12, 13, 15, 18, 19 Rosy (Black) , 42 Flicker, Northern, 66 Flycatcher, Acadian, 29, 43 Alder, 189 Ash-throated, 44, 64, 66 Dusky, 5, 14, 15, 18, 19 Dusky-capped, 37 Gray, 6, 18, 19, 20, 67 Great Crested, 37, 44, 113 Hammonds, 192 Least, 37, 113, 153, 159 Olive-sided, 5, 15, 18 Scissor- tailed, 37. 114 Western, 6, 153-159 Willow, 66, 189 Yellow-bellied, 153-160 Fratercula cirrhata, 99 cornicuiata, 99-102 Fregata magnificen s, 87, 89, 90 Frigatebird, Magnificent, 87, 89. 90 Fu/ica americana , 66 a. alai, 175-181 Fulmar, Northern, 83 Fulmarus glacialis, 83 Gadwall, 65 Gallinula chloropus sanduicensis. 175 Gatz, Thomas A., Martin D. Jakle, Richard L, Glinski and Gale Monson, First nesting records and current status of the Black-shouldered Kite in Arizona. 57-61 Gauia adamsii, 33. 107, 118, 119 Geothlypis trichas, 65, 67 Glaucidium gnoma, 14. 15. 25-28 Glinski. R.L., see Gatz, T. Gnatcatcher, Blue-gray. 9. 18, 19 Godwit, Bar-tailed, 35 Hudsonian. 110 Goldfinch, American, 65, 68 Lawrence’s, 13, 18 Lesser, 13, 18 Goose, Emperor, 34 Grackle, Common, 42 Graybill, M.R., see Pitman, R. Grebe, Eared, 81 Grosbeak, Black-headed, 65, 68, 143-145 Evening, 63, 68 Ground-Dove, Ruddy, 45 Grouse, Blue, 64, 66 Sage. 64, 66 Grus canadensis canadensis, 151 c. tabida, 185-186 Guillemot, Pigeon, 169, 171, 172 Gull, California, 88, 147, 187 Common Black-headed, 36, 75, 111 Great Black-backed, 42 Herring, 88, 147 Iceland, 119 Laughing, 75, 88 Little, 36, 110 Mew, 147-150, 187-188 Ring-billed, 147 Thayer’s, 147-150 Western, 88 Gygis alba, 131-141 Gymnorhinus cyanocephalus. 64. 65. 67 Gyrfaleon, 34 Haiiaeetus leucocephalus, 124, 126 Hanka. Ladislav R., Recent altitudinal range expansion by the Brown- headed Cowbird in Colorado, 183-184 Harrier, Northern. 124, 126 Haskins, J., see Ellis, K. Hawk, Coopers, 124 Ferruginous, 124, 126 Red-shouldered, 124. 126 Red-tailed. 57. 64, 65. 124-128 Rough-legged, 124. 126, 128 Sharp-shinned. 14, 15. 126, 143 Swainson's, 126 White-tailed, 118 Zone-tailed. 34. 110 Hawk-Owl, Northern. 24 Hayes. David, Unusual Western Bluebird eggs, 146 Helmitheros uerrriivorus. 40. 44, 116. 120 Henderson. R.P.. see DeSante. D. Heteroscelus breuipes. 29 193 Himantopus mexicanus knudseni, 175-181 Hirundo pyrrhonota, 49-50. 67 rustica. 49-50. 67 Hummingbird, Black-chinned, 66 Broad-billed. 37, 112. 119 Hylocichla mustelina. 38. 114 Ibis, White, 120 Icteria uirens. 65, 68 Icterus galbula , 64, 68 Ictinia mississippiensis. 34, 110 Inkiey, Douglas B., First record of the Yellow-throated Warbler in Wyoming, 95-97 Jaeger, Parasitic, 88 Pomarine, 88 Jakle, M.D., see Gatz, T. Jay, Blue, 28 Pinyon, 64, 65, 67 Steller’s, 8, 15, 18 Johnson, Ned K. and Carla Cicero, Breeding avifauna of San Benito Mountain, California: evidence for change over one-half century, The, 1-23: see DeSante, D. Junco, Dark-eyed, 12, 15, 68 Junco hyemalis pinosus, 12, 15, 68 Kestrel, American, 66, 124. 126-128 Killdeer, 66, 69 Kingbird, Thick-billed. 114 Western. 66 Kite. American Swallow-tailed. 42 Black-shouldered. 57-61. 124. 126 Mississippi, 34. 110 Kittiwake, Black- legged. 83. 88 Landry, R.E., see McCrary. M. Lanius ludouicianus. 64. 67 Larus argerifafus, 88, 147 atricilla. 75. 88 californicus. 88. 147. 187 canus. 147-150. 187-188 delawarens is. 147 glaucoides, 119 marinus. 42 minutus. 36. 110 occidentalis. 88 ridibundus. 36. 75, 111 thayeri. 147-150 Lehman. Paul, review by. 52-54; Calls of Alder and Willow flycatchers. 189 Leucosticte arctoa atrata, 42 LeValley, R., see DeSante, D. Limosa haemastica, 110 lapponica. 35 Littlefield, Carroll D.. Record of preterritorial copulation by Sandhill Cranes. A, 151 Loon. Yellow-billed, 33, 107, 118. 119 Magpie. Black-billed, 64-67 Mallard. 65 Martin, Purple. 7. 18 McCrary. Michael D., Robert L. McKernan, William D Wagner and Ross E. Landry. Roadside raptor census in the San Jacinto Valley of southern California. 123-130 McKernan, R L., see McCrary, M. Meadowlark. Western. 64. 68 Melanerpes erythrocephalus. 37 lewis. 64. 66, 69 Melospiza melodia. 68 Merganser, Common, 14. 15. 16 Mergellu S albellus. 29. 34 Mergus merganser. 14. 15. 16 Merlin. 124 Miles, Dorothy H., White Terns on Oahu produce siblings five months apart, 131-141 Miller. Gary S.. S. Kim Nelson and Will C. Wright. Two-year old female Spotted Owl breeds successfully. 93-94 Molothrus ater. 68. 183-184 Monson. G.. see Gatz. T. Moore. S.W.. see DuBowy. P. Moorhen. Common (Hawaiian). 175 Morlan, Joseph. Eighth report of the California Bird Records Committee. 105-122 Motacilla alba. 29. 31. 38 flaua. 29. 105. 114. 115 lugens. 29. 31. 38 Murre. Common. 169-172 Thick-billed, 36 Murrelet, Kittlitz's. 29. 36 Myiarchus cinerascens. 44. 64. 66 crinitus. 37. 44. 113 tuberculifer. 37 Myioborus pictus. 116. 120 Nelson. S. K.. see Miller. G. 194 Night-Heron, Yellow-crowned, 34, 109 Nighthawk, Common, 66 Numerous arquata, 188 Nuthatch, Pygmy, 8, 14, 15, 18 Nycticorax violaceus, 34, 109 Oceanites oceanicus, 33, 108 Oceanodroma furcata, 169, 171 ieucorhoa , 84, 88, 90 melania, 84 tethys, 84 Ogden, R.R., see Emlen, J. Oporornis agilis, 40, 44 formosus, 40 Philadelphia, 40, 44, 116, 117, 158 tolmiei, 14, 15, 67 Oreortyx pictus, 4, 15 Oriole, Northern, 64, 68 Osprey, 124 Otus flammeolus, 14, 15, 25-28 kennicottii, 14, 25-28, 66 Owl, Barred, 29, 37, 112 Burrowing, 124 Flammulated, 14, 15, 25-28 Great Horned, 25-28, 66, 126 Long-eared. 25-28 Northern Saw-whet, 5, 14, 15, 18, 19, 25-28 Short-eared, 126 Spotted, 14, 15, 25-28, 93 Pandion haliaetus, 124 Partridge, Gray. 121 Parus gambeli, 14. 15, 64. 67 inornatus, 8 rufescens, 14, 15. 16 Passerculus sandwichensis, 68, 69 Passerina amoena. 65. 68. 69 ciris. 41. 117 cyanea, 29 Paton, Peter W.C.. J. Michael Scott and Timothy A. Burr. American Coot and Biack-necked Stilt on the island of Hawaii, 175-181 Pelecanus occidentals, 169. 171 Pelican, Brown, 169, 171 Perdix perdix. 121 Petrel, Cape, 42 Cook's, 29, 33, 84 Cook’s/Mas Atierra, 29, 33 Mottled. 108 Steineger's, 33 Peucedramus taeniatus. 45. 120 Pewee. Greater. 112 Phaethon aethereus. 84. 90 Phaiacrocorax auritus, 109 oliuaceus, 34, 108 pelagicus, 169, 171 pennicilatus, 87, 169, 171 Phalaenoptilus nuttal/ii, 64, 66 Phalarope, Red, 87, 100 Phalaropus fulicarius, 87, 100 Phasianus co/chicus, 64, 66 Pheasant, Ring-necked, 64, 66 Pheucticus melanocephalus, 65, 68, 143-145 Philomachus pugnax, 36, 42 Phoebe, Say's. 66 Phylloscopus fuscatus. 31 Pica pica, 64, 67 Picoides tridactylus, 43, 119 villosus, 5, 15 Pipilo chlorurus. 68 erythrophthalmus 65, 68 fuscus, 51 Pipit. Red-throated, 38, 40, 114 Sprague’s, 38. 44 Water, 16 Piranga ludouidana, 11. 14, 15. 18, 68 olivacea. 41, 117 Pitman, Robert L., Marine birds of Alijos Rocks, Mexico. The. 81-92; and Michael R. Graybill, Horned Puffin sightings in the eastern Pacific, 99-102 Plover, Mongolian, 110 Piping, 34, 42 Wilson’s. 42 Podiceps nigricollis, 81 Polioptila caerulea, 9. 18. 19 Polysticta s telleri, 105. 110 Pooecetes gramineus. 64, 68 Poorwill. Common, 64. 66 Progne subis. 7, 18 Protonotaria citrea, 39. 41. 116 Psaltriparus minimus. 50, 67 Pterodroma cookii, 29. 33, 84 cookii/P. defilippiana, 29. 33 inexpectata, 108 longirostris, 33 Ptilogonys cinereus. 45 Puffin, Horned, 99-102 Tufted, 99 Puffinus auricularis. 84 creatopus. 169 griseus, 84, 169. 171 opisthomelas. 84 Pygmy-Owl. Northern. 14. 15. 25-28 195 Quail, California, 64, 66 Mountain. 4, 15 Quiscalus quiscula, 42 Raven, Common, 64, 67 Redshank, Spotted, 105, 110 Redstart, Painted, 116, 120 Riparia riparia, 65, 67 Rissa tridactpla. 83, 88 Ritchison, Gary, Vocalizations of the Black-headed Grosbeak, 143-145 Robin, American, 9, 15, 16, 19, 64. 67, 69 Ruff, 36, 42 Rpnchops niger, 78 Salpinctes obsoletus. 67 Sandpiper, Buff-breasted, 36, 110 Curlew, 35 Semipalmated, 35, 118 Sharp-tailed, 35 Spotted, 65, 66 White-rumped, 35 Sagornis saga, 66 Schaffner, Fred C., Royal Tern nesting attempts in California: isolated or significant incidents?, 71-80 Scott, J.M.. see Paton. P. Screech-Owl, Western. 14, 25-28, 66 Seedeater. White-collared, 45 Shallenberger, Robert J., Hawaii’s birds (review). 103-104 Sharp, Brian, Avifauna! changes in central Oregon since 1899, 63-70 Shearwater. Black-vented. 84 Pink-footed, 169 Sooty, 84. 169, 171 Streaked, 108 Townsend’s, 84 Shrike, Loggerhead, 64, 67 Sialia currucoides. 67, 146. 161-168 mexicana, 146 sialis. 146. 162. 163, 166 Silky-Flycatcher. Gray. 45 Siskin. Pine. 14. 15 Sitta pggmaea. 8. 14. 15. 18 Skimmer, Black, 78 Skylark, Eurasian.- 37 Smew. 29. 34 Somateria spectabilis. 34. 109 Sparrow, Baird's. 41 Black-chinned. 11 Black-throated. 51. 68. 69 Brewer's. 64. 68. 69 Cassin’s. 41, 51 Chipping, 64, 68 Lark, 64, 68 LeConte’s, 42 Sage, 12 Savannah, 68. 69 Sharp-tailed, 42. 117 Song. 68 Vesper, 64, 68 White-crowned, 14. 15 Spiza americana. 123 Spizella atrogularis caurina. 11 breweri, 64. 68. 69 passerine. 64. 68 Sporophila torqueola, 45 Starling, European, 64. 67 Stelgidoptergx serripennis. 67 Stercorarius parasiticus. 88 pomarinus. 88 Sterna caspia. 71-78 elegans. 71-78 forsteri. 78 fuscata. 71, 88. 90. 105. Ill maxima. 71-80 sandvicensis. Ill Stilt. Black-necked (Hawaiian). 175-181 Stint. Rufous-necked. 35. 110 Storm-Petrel, Black. 84 Fork-tailed. 169. 171 Galapagos. 84 Leach’s. 84. 88. 90 Wilson’s, 33, 108 Streptoprocne zonaris. 105. 112 Strix occidentalis. 14. 15. 93 o. occidentalis. 25-28 uaria. 29, 37. 112 Sturnella neglecta. 64. 68 Sturnus vulgaris. 64. 67 Sula dactglatra. 31. 85. 87. 90 leucogaster. 33. 108 Surnia ulula. 24 Swallow. Bank. 65. 67 Barn. 49-50. 67 Cliff. 49-50. 67 Northern Rough-winged. 67 Tree. 49-50 Violet-green, 7, 15. 18. 49-50. 67 Swan. Trumpeter. 34 Swenson. Jon E., Reproduction of Mountain Bluebirds in southcentral Montana. 161-168 Swift. Vaux’s. 65. 66 White-collared. 105. 112 196 Tachycineta bicolor, 49-50 thalassina. 7 . 15, 18. 49-50, 67 Tanager. Scarlet, 41, 117 Western. 11, 14, 15, 18, 68 Tattler, Gray-tailed, 29 Teal, Baikal, 109 Blue-winged, 180 Cinnamon, 65 Tern, Caspian. 71-78 Elegant, 71-78 Forster’s, 78 Royal, 71-80 Sandwich, 111 Sooty, 71, 88, 90, 105, 111 White, 131-141 Texas Ornithological Society, Checklist of the birds of Texas, (review), 103 Thrasher, Curve-billed, 38, 44, 98 Thrush. Hermit, 14, 15 Swainson's, 14, 15 Wood, 38, 114 Titmouse, Plain, 8 Tove, Michael H., First Utah records of Thayer’s and Mew gulls, with com- ments on their regional distribution and status, 147-150 Towhee, Brown, 51 Green-tailed. 68 Rufous-sided, 65, 68 Toxostoma curuirostre. 38. 44, 98 Tringa erythropus, 105, 110 Troglodytes aedon, 146, 162 troglodytes, 14, 15 Tropicbird, Red-billed, 84, 90 Tryngites subruficollis, 36, 110 Turdus migratorius, 9, 15, 16, 19, 64, 67, 69 Turnstone, Ruddy, 71 Tyrannus crassirostris, 114 forficatus, 37, 114 uerticalis, 66 Tyto alba, 25-28, 126 Uria aalge, 169-172 lomuia. 36 Unitt, Philip, The Birds of San Diego County (review). 52-54; Plumage wear in Vireo beltii, 189-190 Veery, 44, 114, 120 Verm iv ora celata, 67 chrysoptera, 39, 116 peregrina. 159 ruficapilla, 10. 14, 15, 18 Vireo, Bell’s, 189-190 Hutton’s, 10, 18, 19 Philadelphia, 39, 44, 115, 158 Red-eyed, 39 Solitary, 9, 15, 18 Warbling, 44, 65, 67 White-eyed, 39, 115 Yellow-throated, 39, 115 Vireo bellii, 189-190 flavifrons, 39, 115 giluus, 44. 65, 67 griseus, 39, 115 huttoni, 10, 18, 19 olivaceus flauouiridis, 39 philadelphicus, 39, 44, 115, 158 solitarius cassinii, 9, 15, 18 Vulture, Black, 31, 126 Wagner, W.D., see McCrary, M. Wagtail, Black-backed, 29, 38 White. 29, 38 White/Black-backed, 31 Yellow, 29, 105, 114, 115 Warbler, Bay-breasted, 158 Biackpoll, 159 Black-throated Gray, 11, 18, 64, 67 Black-throated Green, 158 Canada, 158 Cape May, 158 Cerulean, 40, 116 Connecticut, 40. 44 Dusky, 31 Golden-winged, 39, 116 Grace’s, 39 Hooded, 29 Kentucky, 40 MacGillivray’s, 14, 15, 67 Magnolia, 159 Mourning, 40, 44, 116, 117, 158 Nashville, 10, 14, 15, 18 Olive, 45, 120 Orange-crowned, 67 Pine, 39. 120 Prothonotary, 39, 41, 116 Red-faced, 116 Tennessee, 159 Wilson’s, 14, 15. 65, 68 Worm-eating, 40, 44, 116, 120 Yellow, 64, 67, 183 Yellow-rumped, 10, 14, 15. 16, 19 Yellow-throated, 39. 95-97, 116 Webster, Richard, reviews by, 103-104 Whistling-Duck, Black-bellied, 121 Wigeon, American, 65 197 Wilsonia canadensis, 158 citrina, 29 pusilla, 14, 15, 65, 68 Winter, Jon, Partial albinism in a melanistic Mew Gull, 187-188 Wood-Pewee, Eastern, 112, 113, 120 Western, 5, 15, 16, 18, 19, 65, 67, 69 Woodpecker, Hairy, 5, 15 Lewis’, 64, 66, 69 Red headed, 37 Three-toed, 43, 119 Wren, Canyon, 67 House, 146, 162 Rock, 67 Winter, 14, 15 Wrentit, 15 Wright, W.C., see Miller, G. Xanthocephalus xanthocephalus, 65, 68 Yellowthroat, Common, 65, 67 Zenaida macroura, 66, 98 Zonotrichia leucophrys, 14, 15 Sabine’s Gulls Sketch by Tim Manolis 198 Volume 16, Number 4, 1985 Occurrence and Identification of the Yellow-bellied Flycatcher on Southeast Farallon Island, California David F. DeSante, Ned K. Johnson, Ron LeVatley and Robert P. Henderson 153 Reproduction of Mountain Bluebirds in Southcentral Montana Jon E. Swenson 161 Nearshore Flights of Seabirds Past Yaquina Estuary, Oregon, During the 1982 and 1983 Summers Range D. Bayer 169 American Coot and Black-necked Stilt on the Island of Hawaii Peter W.C. Paton, J. Michael Scott and Timothy A. Burr 175 NOTES Recent Altitudinal Range Expansion by the Brown-headed Cowbird in Colorado Ladislav R. Hanka 183 Unusual Nest Site for Greater Sandhill Cranes in Colorado Kevin L. Ellis and James Haskins 185 Partial Albinism in a Melanistic Mew Gull Jon Winter 187 Calls of Alder and Willow Flycatchers Paul Lehman 189 Plumage Wear in Vireo bellii Philip Unitt 189 INDEX Mildred Comar 191 BULLETIN BOARD 199 Cover photo by Bruce Maxwell: Crested Auklet ( Aethia cristatella) , Pribilof Islands, Alaska, June 1983. Manuscripts should be sent to Alan M. Craig, P.O. Box 254, Lakeview, CA 92353. For matters of style consult Suggestions to Contributors to Western Birds (6 pp. mimeo available at no cost from the Editor) and Council of Biology Editors Style Manual 4th edition, 1978 (available from the American Institute of Biological Sciences, 1401 Wilson Boulevard, Arlington, VA 22209 for $12.00). Papers are desired that are based upon field studies of birds, that are both understand- able and useful to amateurs, and that make a significant contribution to scientific literature. Appropriate topics include distribution, migration, status, behavior, ecology, population dynamics, habitat requirements, the effects of pollution, the techniques for identifying, cerisusing, sound recording and photographing birds in the field. Papers of general interest will be considered regardless of their geographic origin, but particularly desired are papers dealing with studies accomplished in or bearing on Rocky Mountain states and provinces westward, including Alaska and Hawaii, adjacent portions of the Pacific Ocean and Mexico, and western Texas. Reprints can be ordered at author’s expense from the Editor when proof is returned or earlier. Good photographs of rare and unusual birds, unaccompanied by an article but with caption including species, date, locality and other pertinent information, are wanted for publication in Western Birds. Submit photos and captions to Photo Editor. ! I