ROCKY MOUNTAIN FRONT RAPTOR SURVEY DECEMBER 1982 - AUGUST ]98 4 CONTRACT NO. FWS-6-81-112 STATE DOCUMENTS COLLECTION J UN 0 2 IQQfl MONTANA STATE LIBRARY 1515 E. 6th AVE. HELENA, MONTANA 59620 FUNDED BY: UNITED STATES FISH AND WILDLIFE SERVICE PREPARED BY: KRiSTi Dubois MONTANA DEPARTMENT OF FISH, WILDLIFE AND PARKS 1984 MAR 1 - 1989 MAR 2 9 1995 MONTANA STATE LIBRARY S S98.9 F2rmf 1984 e.1 DuBois Rocky Mountain front raptor survey, Dece 3 0864 00050440 0 ACKNOWLEDGEMENTS Many people have offered their support and assistance during this study. The project was initiated and promoted by Bob Martinka, Jim Posewitz, Arnold Olsen, Glenn Erickson, Jim Mitchell, and Dan Vincent of the Montana Department of Fish, Wildlife and Perks; and Wayne Brewster of the U.S. Fish and Wildlife Service. Tim Andryk, Keith Aune , Dale Becker, Tom Bivens, Frances Cass.irer, Sarah Cobb, Tad Day, Wayne Elliot, Ron Escano, Bert Goodman, Dan Hook, Helga Ihsle-Pac, Gayle Joslin, Mike Madel, John McCarthy, Gary Olson, Tom Stivers, Ted Wenzel, Cliff Youmans, and Lewis Young provided technical advice, field assistance, and information. Pilots, Gene Sherman and Doug Getz provided successful, aerial surveys in an adverse flying climate. Larry Copenhaver contributed the cover drawings for the reports. Fay Moore and Serena Andrew typed and edited the annual reports, often from less-than-readable writing. Bert Lindler provided much-needed moral support. Western Geophysical and. Sefel Geophysical offered the use of their helicopters gratis. Special thanks to the landowners along the Front for their warm hospital ity . This project was conducted under a U.S. Fish and Wildlife Service contract (FWS-6-81-112) through Region 4 of the Montana Department of Fish, Wildlife and Parks. (i) Abstract A raptor survey was conducted from December 1981 through August 1984, in a 4700 sq km study area on the Rocky Mountain Front, northcentral Montana. The purpose of the study was to gather baseline information on raptor distribution, abundance, habitat use, and productivity to be used to monitor changes in the raptor community brought about by man's activities and to develop protective stipulations. Major activities included oil and gas exploration, timber harvest, livestock grazing, recreation, subdivisions and farming. Nonsystematic ground and aerial surveys were employed, with emphasis on cliff-nesting species. The golden eagle, northern harrier, prairie falcon, Swainson's hawk, red-tailed hawk, and American kestrel were the most common diurnal species. Estimated nesting densities (pairs per 100 sq. km) were: golden eagle - 0.8, northern harrier - 1.3, red-tailed hawk - 1.2, Swainson's hawk - 1.0, ferruginous hawk - 0.2, and prairie falcon - 1.1. The great horned owl and northern saw-whet owl were the most commonly encountered nocturnal species. The nesting density of great horned owls was estimated to be 1.0 pairs per 100 sq. km. The total nesting population density was calculated to be about 447 pairs or 9.5 pairs per 100 sq. km for a total of 18 raptor species. Cliff and riparian habitats were the most important nesting habitats for the raptor community as a whole. A total of 1,142 raptors was sighted while driving 27546 km of roads, for a total of 41.5 birds sighted per 1000 km driven (18 species sighted) . Suggested management goals were to maintain the healthy and diverse raptor population, and to maintain suitable habitat for possible future reoccupation by nesting bald eagles and peregrine falcons. Stipulations were proposed for the following management categories: 1) Areas occupied by nesting endangered species, 2) potential nesting habitat for endangered species, 3) areas occupied by nesting non-endangered species of special interest (golden eagle, prairie falcon, ferruginous hawk, merlin, northern goshawk) , 4) potential nesting habitat for special interest species and other more common species, and 5) areas not used for nesting, including foraging areas. 801/3 TABLE OF CONTENTS PAGE I. Introduction R II. Study Area 9 A. Vegetation and Topography 9 B. Climate „ 11 III. Summary of previous studies 12 IV. Methods 13 . A. Vegetation 13 B. Nesting Surveys 13 1. Definition of status terms 14 C. Great horned owl hooting surveys 14 D. Bald eagle winter surveys 15 E. Road Surveys 15 V. Results 16 A. Vegetation 16 B. Nesting surveys 18 1. Diurnal species 18 2. Nocturnal species 31 C. Great horned owl hooting surveys 31 D. Bald eagle winter surveys 32 E. Road surveys 33 VI. Discussion 33 A. Nesting population density 33 B. Impacts of man's activities on nesting populations 35 1. Direct mortality 35 2. Loss of productivity 36 a. Pesticides , 36 b. Disturbance 36 -Impacts observed on the study area 36 -Impacts of this study 37 1. Ground surveys 37 2. Fixed-wind aircraft surveys 37 3. Helicopter surveys 37 3. Elimination of nesting habitat 38 4. Reduction of prey base 39 5. Cumulative impacts 39 VII. Management Recommendations 39 General Raptor Guidelines 39 Type 1 . Areas occupied by nesting bald eagles or peregrine falcons 40 Type 2. Potential nesting habitat for bald eagles or peregrine falcons 41 3 Type 3. Areas occupied by nesting species of special concern Type 4. Potential nesting habitat for species of special concern and other common raptor species . Type 5. Areas not used for nesting (including foraging areas) Enhancement Activities for Raptors VI 1 1 . Summary .... Literature Cited LIST OF TABLES 1. Percentages of each habitat in the 4700 sq km Rocky Mountain Front study area, northcentral Montana. 2. Nest supports used by six species of raptors on the Rocky Mountain Front, northcentral Montana, 1982-1984. 3. Average number of young fledged per successful nest for seven raptor species on the Rocky Mountain Front, northcentral Montana, 1982-1984. 4. Nesting chronology observed for six raptor species on the Rocky Mountain Front, northcentral Montana, 1982-1984. 5. Numbers of great horned owls detected along hooting survey routes in four habitats along the Rocky Mountain Front, northcentral Montana, 1983. 6. Relative abundance of raptor species observed while driving 27546 km along roads on the Rocky Mountain Front, northcentral Montana, December 1981-August 1984. 7. Estimated breeding densities for 18 species of raptors in the 4700 sq km Rocky Mountain Front Study area, northcentral Montana, 1982-1984 (based on active nests and sightings of territorial pairs) . 8. Comparison of the nesting density of raptors in the Rocky Mountain front study area, northcentral Montana, with areas in other western states. 9. Recommended buffer zones and average dates of nesting seasons for five species of raptors on the Rocky Mountain Front, northcentral Montana. 5 I LIST OF FIGURES 1. Raptor study area, Rocky Mountain Front, northcentral Montana . 2. Directional exposure of cliffs located in the Rocky Mountain Front study area, northcentral Montana. 3. Directional exposure of golden eagle nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. 4. Directional exposure of ferruginous hawk nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. 5. Directional exposure of prairie falcon nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. LIST OF APPENDIX TABLES AND FIGUPES A. Climatological data from three reporting stations on the Rocky Mountain Front, northcentral Montana. B. Approximate portions of the Rocky Mountain Front study area surveyed in previous raptor studies. C. Habitat mapping categories used for the Rocky Mountain Front study area, northcentral Montana. D. Number of aerial survey hours conducted on the Rocky Mountain Front, northcentral Montana, 1982-1984. E. Areas covered during aerial surveys on the Rocky Mountain Front, northcentral Montana, 1982-1984. F. Habitat types on the Rocky Mountain Front raptor study area, northcentral Montana. G. Breeding status of the raptor species found on the Rocky Mountain Front, northcentral Montana. H. Nest-site characteristics of golden eagle nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. I. Prey species' observed in the diets of five raptor species on the Rocky Mountain Front, northcentral Montana, 1982-1984. J. Nest-site characteristics of red-tailed hawk nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. K. Nest-site characteristics of Swainson's hawk nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. L. Nest-site characteristics of ferruginous hawk nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. M. Nest-site characteristics of prairie falcon nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. N. Nest-site characteristics of great horned owl nests located along the Rocky Mountain Front, northcentral Montana, 1982-1984. 7 I . INTRODUCTION The Sawtooth Range in northcentral Montana, commonly known as the East Front of the Rocky Mountains, is thought to have a high potential for gas and oil production. Exploration for gas and oil has increased dramatically and undergone a revolution in technology in recent years, and the first commercial gas wells along the East Front went into production in 198?. The East Front also supports an abundant and diverse wildlife resource. Extensive gas and oil development in combination with other land uses such as logging, recreation, and agriculture could cause conflicts with the wildlife resources (Olson 1981, Ihsle 1982, Andryk 1983) . The Interagency Monitoring Program was initiated in 1980 to coordinate data collection on wildlife along the East Front. Agencies involved were the Forest Service (FS) , Bureau of Land Management (BLM) , Fish and Wildlife Service (FWS) , and Montana Department of Fish, Wildlife and Parks (FWP) . The specific objectives were to 1) monitor wildlife displacement caused by human activities, 2) monitor wildlife populations to determine changes caused by human activities, and 3) monitor changes in wildlife habitat due to human activities, and the possible effects to wildlife. A raptor survey was initiated in December 1981 as part of the Interagency Monitoring Program to provide an adequate data base to be used in making responsible management decisions involving development of energy and other resources. Specific objectives were to: 1) determine distribution, abundance and habitat use of the raptor species found on the East Front; 2) describe nesting habitat and productivity of nesting raptors; 3) delineate suitable nesting habitat for the bald eagle (Haliaeetus leucocephalus) and peregrine falcon (Falco peregrinus) , regardless of current occupancy; 4) delineate winter concentration areas for bald eagles; 5) determine responses of raptors to human activities, when possible; and 6) develop protective stipulations and guidelines to be used by land management agencies when planning land use activities. II. STUDY AREA The study area, located in parts of Teton, Lewis and Clark, and Pondera Counties was bounded on the north by Birch Creek, the south by highway 200, the east by highways 89 and 287, and the west by the boundaries of the Bob Marshall Wilderness area, the Scapegoat Wilderness area, and the Continental Divide (Figure 1). The 4700 sq km study area was divided into three segments. The north segment (1425 sq km) between Birch Creek and the Teton River, was surveyed in 1983. The middle segment (1425 sq km) between the Teton River and the Sun River, was surveyed in 1982. The south segment (1850 sq km) between the Sun River and highway 200, was surveyed in 1984. Public lands in the study area are managed by the Lewis and Clark National Forest and Helena National Forest (25%) , Bureau of Land Management (3%), Montana Department of Fish, Wildlife, and Parks (The Sun River, Ear Mountain, and Blackleaf Game Ranges, totaling 3%) , and the Department of State Lands (School Trust Lands - 10%) . The remaining 59% is private land. The major land uses are livestock grazing, irrigated and dryland farming, timber harvest, developed and dispersed recreation, and housing developments. A. VEGETATION AND TOPOGRAPHY Physical characteristics of various portions of the study area have been previously described in Andryk (1983) , Aune and Stivers (1983), DuBois (1983), Erikson (1972), Frisina (1974), Ihsle (1982), Joslin (1983), Kasworm (1981), Knight (1970), Mudge (1972a, 1982b), Picton (1960), and Schallenberger (1966). The study area straddles the eastern edge of the Rocky Mountains, with the eastern two-thirds lying in the Great Plains and the western one-third lying in the Rocky Mountains. The eastern two-thirds is characterized by gently-rolling or flat topography, with elevations ranging from 1158 meters to 1371 meters. Grasslands predominate, traversed by narrow riverine systems. Extensive areas of farmland lie mainly in the eastern one third of the study area. Primary crops are wheat and alfalfa. Nearly all grasslands are grazed by cattle or sheep. Riparian habitats range from mesic grass/shrub coulees to extensive cottonwood forests along the major river bottoms. Major drainages include Birch Creek, Dupuyer Creek, Teton River, Deep Creek, Sun River, Elk Creek, and the Dearborn River. 9 BLACKFEET Figure 1. Raptor study area, Rocky Mountain Front, northcentral Montana . 10 The western one-third of the study area lies in the Sawtooth Range of the Rocky Mountains, commonly known as the East Front or the Rocky Mountain Front. Topography consists of rugged, parallel ridges formed by thrust-faulting of sedimentary rocks. These ridges have vertical east faces, and moderate to steep west-facing slopes. Spectacular cliffs on the east faces provide abundant nesting habitat for several species of raptors. Most ridge-tops are 2100-2400 meters in elevation, with some peaks reaching up to 2700 meters. Vegetation consists of a complex mosaic of conifer forest, aspen (Populus tremuloides) stands, grassland parks, sparse wind-blown stands of stunted conifer trees, and bare rock. The transition between the rugged Sawtooth Range and flat plains is abrupt, with few foothills. B. Climate Climatic conditions vary with elevational ranges and topography. Average annual precipitation varies from 31 cm at Choteau to over 127 cm in the Sawtooth Range. The average growing season varies from 110 days at Choteau to 50 days in the Sawtooth Range north of the Teton River. The mean annual temperature is approximately 5 degrees C, and monthly averages range from minus 6 degrees C in January to 19 degrees C in August. The weather is characterized by strong, southwest winds, especially along the east face of the mountains. The winter and spring months of 1982 averaged colder than normal. This may have influenced the nesting phenology of some of the raptor species. Climatological data for three reporting stations are presented in Appendix A. 11 III. SUMMARY OF PREVIOUS STUDIES Six studies dealing with birds of prey had been conducted in or adjacent to the study area prior to the initiation of this study. Schallenberger (1975) conducted a raptor survey on the Lewis and Clark National Forest from April to July 1975. His survey was primarily limited to the eastern edge of the National Forest from the north fork of the Dearborn River to the north end of Walling Reef. Gramlich (1979) conducted a raptor survey on Bureau of Land Management Lands along the Rocky Mountain Front, from 15 May 1979 to 22 June 1979. Specific areas covered included Steamboat Mountain, Sheep Mountain, Haystack Butte, Swallow Canyon, Cutrock Gorge, Green Timber Gulch, north and south forks of Deep Creek, South Fork Teton Canyon north of Indian Head Rock, and the area between Chicken Coulee and Antelope Butte. Wenzel (1982) summarized incidental observations of raptors made while conducting other field studies along the Front, between the Dearborn River and Birch Creek. His observations encompassed National Forest, BLM, state, and private lands. Ellis (1979) conducted a behavioral study on golden eagles in an area adjacent to the study area from 1970 to 1973 . Some of his data on nest sites, pesticides, and productivity are applicable to the East Front study area. Leedy (1972) conducted a study in 1971 and 1972 on the effects of insecticides on prairie falcons. A portion of one of his study areas overlapped the southern half of the East Front study area. His data on prairie falcon productivity and pesticide contamination are applicable to the East Front study area. Crenshaw (1979) conducted a faunal survey of the Pine Butte Swamp area during 1979. His survey included songbirds, small mammals and furbearers as well as raptors. The portions of the study area covered in these surveys are shown in Appendix B. 12 IV. METHODS A. METHODS - VEGETATION Habitat types on the study area were combined into broad categories, best described as biome types (grassland, riparian, conifer forest, conifer savannah, agricultural farmland, cliff and water) . Cliff habitat, though not a vegetational type, was mapped separately because of its importance as raptor nesting habitat. A description of each category is provided in Appendix C, including habitat types described by Mueggler and Stewart (1980) and Pfister et al. (1977). Habitat categories were delineated on 1:62500 and 1:24000 scale U.S.G.S. topographic maps. U.S. Forest Service P.I. (Photo Interpretation) maps were used to delineate conifer forest stands of greater than 40 percent canopy coverage. The conifer scrub-savannah category included stunted, windblown stands of conifers, scattered large trees, and conifer stands with less than 40 percent canopy coverage. The division was based upon suitability for nesting goshawks (Accipiter gentilis) . Conifer stands on non-national forest lands were mapped using aerial photographs. Other habitat categories were mapped using a combination of topographic maps, black and white, color, and color I.R. aerial photos, and land use maps for Teton, Pondera, and Lewis and Clark Counties. Percentages of each type were determined using a dot-grid. The purpose of the habitat map is to provide information on the general distribution and relative proportions of habitats important to nesting raptors. More specific vegetation information can be obtained from Aune and Stivers (1983), Kasworm (1982) and Andryk (1983). The linear extent of the major cliffs on the study area was measured to provide a more meaningful measure of availability. Measurements were taken from U.S.G.S. topographic maps. The general aspect of each section of cliff was also recorded. B . Nesting Surveys Potential nesting areas for raptors were located by ground reconnaissance and use of aerial photographs and topographic maps. These areas were then searched intensively by helicopter, fixed-wing aircraft, and on foot to locate nests and territories of breeding raptors. Funding was insufficient to allow adequate coverage of the entire study area, so most search effort was directed at cliff-nesting species on BLM and national forest lands. Procedures followed those recommended by Call (1978) Fyfe and Olendorff (1976), Boeker (1970) and White and Sherrod (1973). Information from previous studies and from local residents aided this effort. Active nests were visited near fledging time, if possible, to obtain productivity data. During ground surveys, nests were checked with a spotting scope, if possible, to avoid disturbing the birds. Nest visits which required a close approach were made during mild weather if eggs or downy young were present. 13 Pellets and food remains were collected from beneath nests, at perches near nests, and at roosting areas. Most nests were devoid of prey items, resulting in an insufficient sample size for food habits analysis. Therefore, only the occurrence of a prey species in the diet was noted. Helicopter surveys played a major role in locating cliff-nesting raptors, especially golden eagles (Aquila chrysaetos) . An attempt was made to survey all suitable cliffs in the portion of the study area along the East Front at least twice during the nesting season. The first survey was usually conducted in early April, when golden eagles were in the early part of incubation. Surveys conducted later were more likely to miss nests which experienced failure during the incubation or nestling stages. The second survey was usually conducted in mid to late June to obtain brood counts. At this time, most eaglets were nearly full-grown. Adverse weather conditions and scheduling of aircraft delayed some of the surveys, resulting in incomplete data. Golden eagle nests were monitored from the ground when possible, but many nests were either inv areas of poor accessibility or on very high cliffs, making reliable ground checks difficult. Fixed-wing aircraft was used to survey deciduous riparian habitat and grassland habitat for nesting buteos. Appendix D summarizes the number of survey hours using helicopter and fixed-wing aircraft in each year, and Appendix E shows the portions of the study area which were surveyed by air in 1982, 1983 and 1984. The terms used in this report to describe nesting status generally followed those suggested by Postupalsky (1974). Briefly, they are as follows: Occupied - pair present, nesting suspected but not confirmed. Active - confirmed nesting attempt (incubation, eggs, or young observed) . Nest failed - nesting attempt terminated before young could be fledged . Young produced - young observed in nest, fledging not confirmed. Young fledged - young observed to have fledged. Young which were close to fledging-age (completely feathered-out and full-sized) , but still in the nest were counted as fledged. C. GREAT HORNED OWL SURVEYS Nesting great horned owls (Bubo virginianus) were surveyed in 1983 using a method similar to one described by Youmans et al. (1981). Four survey routes were set up, one each in conifer forest, conifer scrub-savannah, grassland, and deciduous tree riparian habitats. Each route was 5 miles (8 km) long with 10 stops placed at 0.5 mile (.8 km) intervals. Taped great horned owl vocalizations were played for approximately one minute. The number of owls responding to the taped calls, gender, and approximate distance and direction (to aid in distinguishing previously-counted individuals) were recorded. Each survey route was conducted once between mid-February and early April on clear, windless nights. Each survey route took about three hours to complete . 14 D. BALD EAGLE WINTER SURVEYS Limited aerial and ground surveys were conducted during the winter to locate bald eagle winter concentration areas. Some of the surveys were conducted in conjunction with the mid-winter bald eagle survey, coordinated by the Raptor Information Center of the National Wildlife Federation. E. ROAD SURVEYS Location, activity, and habitat were recorded for all birds of prey observed while driving, to provide an index of abundance which can be compared to other areas (Woffinden and Murphy 1977, Craig 1978) . This information was gathered peripheral to other activities, so different times of the day and different weather conditions were encountered. Results were summarized as number per 1000 miles and 1000 km traveled. 15 V. RESULTS A. VEGETATION The percentages of each habitat in the study area are presented in Table 1. Grasslands were the most extensive type, covering about half of the study area. Cliffs covered about one percent of the study area. The distribution of habitats in the study area is shown in Appendix F. Table 1. Percentages of each habitat in the 4700 square km Rocky Mountain Front study area, northcentral Montana. Habitat Percent Grassland 47 Conifer savannah 25 Agricultural 11 Conifer forest 10 Riparian 4 Water 1 Cliff 1 Approximately 316 km of cliffs were present in the study area. The majority of cliffs were in the Sawtooth Range in the western one-third of the study area. Directional exposure of the cliffs is shown in Figure 2. The majority of cliffs faced east or northeast . 16 Figure 2. Directional exposure of cliffs located in the Rocky Mountain Front study area, northcentral Montana. 17 B. NESTING SURVEYS 1 . DIURNAL RAPTORS Eighteen species of diurnal raptors were observed during the study or reported by reliable observers (Appendix G) . Twelve species were either suspected or confirmed to be nesting within the study area. The most common nesting species were the golden eagle, northern harrier (Circus cyaneas) , prairie falcon (Falco mexicanus ) , American kestrel (Falco sparverias ) , red-tailed hawk (Buteo jamaicensis) and Swain son's hawk (Buteo swainsonii) . The bald eagle (Haliaeetus leucocephalus) and rough- legged hawk (Buteo lagopus) were present as both migrants and winter residents. A pair of broad-winged hawks (Buteo platypterus) observed in fall 1982 were considered to be accidental migrants in the study area. They are rarely reported in Montana (Skaar 1980) . GOLDEN EAGLE (Aquila chrysaeros) The golden eagle was a common nesting species in the study area. Breeding birds were suspected to be nonmigratory , although some movement to lower elevations in winter was probable. A total of 123 golden eagle nests was found in and adjacent to the study area, most of which were alternate nests for about 37 nesting pairs. Many of the nests were located in groups of up to seven nests on a single cliff. Ninety-seven percent (119 nests) were on cliffs and three percent (3 nests) were in trees (Table 2) . The percentage of tree nests may be underestimated due to the difficulty of locating nests in conifer trees and the concentration of search effort on cliffs. Table 2. Nest supports used by seven species of raptors on the Rocky Mountain Front, northcentral Montana, 1982-1984. Total Number Percenta ges of nests in each type Of Nests Ground Cliff Deciduous Shrub Deciduous Tree Conifer Tree Abandoned Building Golden Eagle 122 . 97 1 2 Red-Tailed Hawk 20 20 80 Swainson's Hawk 32 31 69 Ferruginous Hawk 33 79 21 Prairie Falcon 55 100 Great Horned Owl 11 18 9 64 9 Merlin 4 25 75 Golden eagle nests ranged in elevation from 1250 m to 2386 m, with 73% between 1524 m (5000 ft.) and 2103 m (6900 ft.). Twenty percent were located at or above 2133 m (7000 ft) elevation (Appendix H) . 18 The majority of golden eagle nests had east or northeast exposures (Figure 3) . The directional exposure of 109 golden eagle nests located on cliffs within the study area boundaries was compared to the directional exposure of cliffs located within the study area using the Chi-square test. East, northeast, and southeast exposures were treated separately and all other exposure categories were lumped together due to small expected values (Hoel 1966) . The difference between the golden eagle nest exposures and available cliff exposures was not significant (d.f. = 3, x = 3.255, p = 0.3). This differs from the findings of Mosher and White (1976) who found that nest exposure in a given region was selected on the basis of the thermoregulation needs of the young. Baglien (1975) found that south and east exposures were favored by golden eagles in southwestern Montana. He felt that major downdraft areas (the lee side of ridges interrupting prevailing winds) were unsuitable for golden eagle nesting. This proved not to be the case on the East Front, where most nests were on northeast and east aspects where the strong prevailing southwest winds should have created strong downdrafts. Menkens (1983) concluded that physical characteristics of golden eagle nest sites in trees did not differ significantly from availability in N.E. Wyoming. 1% W E 38% Figure 3. Directional exposure of golden eagle nests located along the Rocky Mountain Front, northcentral Montana, 1982 - 1984. 19 Most of the cliffs used by nesting golden eagles were located in the Sawtooth Range in the western one-third of the study area. Cliff heights (Appendix H) ranged from 6 m to 244 m (mean 67 m) and nest heights ranged from 4.6 m to 152 m (mean 38 m) . Percent height (nest height divided by cliff height times 100) ranged from 12% to 92% (mean 58%) . Conifer forest and conifer savannah were the predominant habitats surrounding cliffs used for nesting. The number of golden eagle young fledged per successful nest (Table 3) was 1.4 young in 1982 (10 nests), 1.25 young in 1983 (12 nests), and 1.25 in 1984 (4 nests). One nest in 1982, three nests in 1983, and 1 nest in 1984 were known to have failed. Several nests have been in use at least since 1975 (Schallenberger 1975) . Nesting chronology is presented in Table 4. Table 3. Average number of young fledged per successful nest for eight raptor species on the Rocky Mountain Front, northcentral Montana, 1982-1984. 1982 1983 1983 No. No. of No. No. of No. No of Species of nests young per nest of nests young per nest of nests young per nest Golden Eagle 10 1. 4 12 ,1. 25 4 1. 25 Northern Goshawk 1 2 1 1 1 2 Red-Tailed Hawk 4 1. 75 7 •-' 1 . 86 4 2. 5 Swainson's Hawk 6 1. 67 9 2. 11 1 2 Ferruginous Hawk 3 3 2 3 Prairie Falcon 5 3. 2 8 3. 8 2 4. 5 Great Horned Owl 2 2 8 2 1 2 Merlin 1 4 1 3 Table 4. Nesting chronology observed for six raptor species on the Rocky Mountain Front, northcentral Montana, 1982-1984. Initiation of Courtship Start of Incubation Hatching Fledging Golden Eagle December 3/ 3 - 4/ 6 4/14 - 5/18 6/23 - 7/28 Red-tailed Hawk March 4/26 - 5/ 4 5/26 - 6/12 7/10 - 7/26 Swainson's Hawk May 5/ 7 - 7/2 6/7-8/6 7/15 - 9/10 Ferruginous Hawk April 4/16 - 5/12 5/16 - 6/10 7/ 5 - 7/25 Prairie Falcon March 4/13 - 5/19 5/13 - 6/19 6/20 - 7/27 Great Horned Owl February 2/11 - 3/ 1 3/18 -4/5 5/20 -6/7 20 Few prey items were found around nests, but eagles were commonly observed carrying jackrabbits and ground squirrels (Appendix I) . Carrion from road kills, winter-killed big game, and dead stock were other food sources, especially in winter. Principal prey species from other studies included white-tailed jackrabbits (Lepus townsendii) and deer fawns (Odocoileus spp.) (Becker 1982) , white-tailed jackrabbits and cottontail rabbits (Sylvilagus spp.) (McGahan 1968), cottontail rabbits, prairie dogs (Cynomys ludovicianus ) and black-billed magpies (Pica pica) (Lockhart 1976; Lockhart et al. 1977), white-tailed jackrabbits (Woodgerd 1952) , and jackrabbits (L. townsendii) and ground squirrels (Spermophilus spp.) (Baglien 1975). Cliff habitat only covered 1% of the study area, yet was used for nesting by 35 pairs of golden eagles (94% of the pairs found nesting on the study area) . Linear distance is probably a more meaningful measure of cliff availability. Approximately 316 km of cliffs were available in the study area. This yields about 9 km of cliff per nesting pair. Thirty-seven pairs of golden eagles were found nesting in the study area (two pairs located greater than one km outside the study area boundary were not counted in density estimates) . This yields a minimum density of 0.8 pairs per 100 sq km. BALD EAGLE (Haliaeetus leucocephalus ) No nesting bald eagles were found during the study, although two historic nest sites were reported by local residents on Elk Creek and the Sun River (Schallenberger 1975, L. Young pers. comm.). Both nests were occupied until the mid to late 1950' s. Nesting bald eagles require lafge c6riifer or deciduous trees which are fairly close (usually within 1.6 km) to large bodies of water (Anthony et al. 1982) . Within the study area, Birch Creek, Teton River, Sun River, Elk Creek, and the North Fork Dearborn River were all considered to be suitable nesting areas. Birch Creek has Swift Reservoir and many small, natural lakes for foraging areas and conifer forests for nesting. The Teton River contains a poor fishery due to floods in 1964 and 1975, but is very close to Bynum Reservoir and Eureka Reservoir which both contain adequate fish populations. Heavy recreational use of these reservoirs may preclude bald eagle use. Gibson Reservoir, Willow Creek Reservoir, Pishkun Reservoir, and numerous ponds and marshes supplement the foraging habitat for bald eagles along the Sun River and Elk Creek. The North Fork Dearborn River is close to Bean Lake and many smaller lakes. Heavy recreational use of some reservoirs may preclude bald eagle use, especially during periods of peak recreational use. All of the mentioned rivers and creeks have segments that are isolated from human activity centers such as roads, campgrounds, houses, and agricultural fields. These areas will remain suitable for nesting bald eagles as long as these disturbance-free segments remain. 21 NORTHERN HARRIER (Circus cyaneus) The northern harrier was one of the most abundant nesting raptor species on the study area. The breeding population was migratory, being on the study area from March through October. Northern harriers occupied grassland, agricultural and riparian habitats throughout the eastern half of the study area. One nest containing three young and two eggs was found at the edge of a hayfield by a ranch hand while mowing the hay. Although he did not mow over the nest, it was later destroyed by predators. Other ranchers also reported encountering harrier nests in hayfields. Mesic grass-sedge or shrub coulees probably were also used by harriers for nesting. Harriers typically nest on the ground in tall, dense grass or low shrubs found in moist coulees, marshes or creek bottoms (Becker 1982, Terres 1980, Call 1978) . Such areas were interspersed with xeric grasslands and agricultural land in the study area. Little effort was spent searching for harrier nests, although fledged young were observed on numerous occasions. At least 85 pairs were observed in the 4700 km study area, yielding a minimum density of 1.8 pairs per 100 sq km. NORTHERN GOSHAWK (Accipiter gentilis) The northern goshawk was present on the study area as a summer resident and rare winter resident. Goshawks were sighted infrequently compared to most other species, but this may indicate low observability rather than a low population. Nesting was confirmed three times, with the observation of fledged young in 1982, a nest in 1983, and fledged young in 1984. A nest was also found by Crenshaw (1979) approximately 400 m from the 1983 nest site. Both nests were located in mature Douglas-fir (Pseudotsuga menziesii) - Lodgepole pine (Pinus contorta) stands on a north-facing slope. Both nests were at an elevation of about 1600 m. Shuster (1980) found that most goshawk nests in Colorado were on slopes with north to east aspects. Goshawks in Oregon preferred dense, mature conifer stands on gentle slopes with northwest to northeast exposure for nesting (Reynolds et al. 1982). Hayward (1983) characterized typical goshawk nesting habitat within the western portion of Region 1 National Forests as mature to overmature conifer forest with a closed canopy on a moderate north-facing slope, usually at or near the bottom of the hillside . Conifer forest suitable for nesting goshawks only covered about ten percent of the study area (Table 1), and was limited to the Sawtooth Range in the western one third of the study area (Appendix F) . Most of the suitable conifer forests occurred in the area south of the Sun River. Goshawks on the study area appeared to initiate nesting activities in late April or early May and fledge young in late July. Huhtala and Sulkava (1981) found that the onset of nest-building by goshawks in Finland was correlated with the mean monthly temperatures in spring. 2? Goshawks in North America generally initiate nesting in April (Jones 1979). Huhtala and Sulkava (1981) also reported poor nesting with many unoccupied nests and smaller clutches after a very cold winter. Goshawks are usually absent from breeding areas for five to six months (Jones 1979). Some populations migrate, while others exhibit localized wanderings. Goshawks were sighted along the Teton River just west of Choteau during winter. It is not known whether these were "local" birds from the Sawtooth Range or migratory birds from other regions. A population estimate for the goshawk was not attempted due to lack of data. The population is suspected to be fairly low, mainly due to the lack of suitable nesting habitat in the study area . RED-TAILED HAWK (Buteo jamaicensis) The red-tailed hawk was a common nesting species on the study area. The breeding population was migratory, being present on the study area from March through October. Nesting red-tailed hawks were mainly associated with riparian habitat in the eastern half of the study area. Eighty percent of the twenty nests located were in cottonwood trees (Populus spp.), and the remainder were on cliffs (Table 2). Wenzel (1982) found an active red-tailed hawk nest in a juniper ( Juniperus spp.) tree adjacent to riparian habitat in the northern part of the study area in 1980. This area was occupied by a pair of red-tailed hawks in 1983, but the nest was not located. Red-tailed hawk nests in conifer trees were more difficult to locate, and little time was spent searching conifer habitat, so use of this type was probably underestimated. Red-tailed hawk nest elevations ranged from 1200 m to 1829 m (Appendix J) . All cottonwood nests were in trees greater than 6 m tall. The average nest height above the ground was higher for red-tailed hawks (7.1 m) than for Swainson's hawks (4.6 m) . Gilmer et al. (1983) reported that red-tailed hawk nests were significantly higher than other buteo nests in central North Dakota. Schmutz et al. (1980) also found that red-tailed hawk nests tended to be higher than Swainson's Hawk nests, and suggested that use of different nest heights reduced competition between the species. Red-tailed hawk nests in the study area tended to be located in clusters which were associated with riperian systems. This uneven distribution may be partially due to uneven coverage of the study area, although most of the large expanses of grassland habitat in the study area are lacking in suitable nest sites for red-tailed hawks. Gilmer et al. (1983) also reported a clumped distribution of red-tailed hawk nests, associated with wooded drainages. Schmutz et al. (1980) found that red-tailed hawks in southeastern Alberta tended to be more common in areas with more aspen timber and ponds. Gaines and Kohn (1982) also concluded that riparian areas were important nesting habitat for red-tailed hawks in Central North Dakota. 23 Riparian habitat only covers 4% of the study area, yet it was the most important nesting habitat for red-tailed hawks. Areas mapped as riparian habitat included riparian types which were unsuitable nesting habitat for red-tailed hawks (shrub and grass-sedge communities) , therefore the actual amount of suitable nesting habitat was smaller than reported. Large areas of conifer forest, conifer scrub-savannah, and cliff habitats which are also considered suitable nesting habitat for red-tailed hawks, are found in the Sawtooth Range in the western portion of the study area. These areas seemed to be sparsely occupied by red-tailed hawks so other environmental factors (prey base, length of growing season, etc.). were believed to be limiting. A more intensive study would be necessary to delineate suitable nesting areas for red-tailed hawks in these habitats. The number of young fledged per successful nest (Table 3) was 1.75 in 1982 (four nests), 1.86 in 1983 (seven nests) , and 2.5 in 1984 (four nests) . This was slightly higher than fledging rates reported by Gilmer et. al (1983) , and about the same as that reported by Peterson (1979) for southeastern Wisconsin. Nesting chronology for the study area is shown in Table 4. The few observations of prey items indicated that red-tailed hawks in the study area fed on voles (Microtus spp.) and ground squirrels. Red-tailed hawks are known to feed on a wide variety of prey, and are not as dependent upon the abundance of one or two prey species as are prairie falcons and golden eagles (U.S. D.I. Bureau of Land Management, 1979). Seidensticker (1970) found that red-tailed hawks in southcentral Montana preyed on 28 species of mammals, birds, reptiles, and fish. Mammals, primarily Richardson's ground squirrels ( Spermophilis richardsonii) , cottontail rabbits (Syl vilagus spp.) and voles comprised 70% of their diet. Uinta ground squirrels (S^ armatus) and voles made up the majority of the diet of red-tailed hawks in Wyoming (Craighead and Craighead 1956). The riparian habitat used for nesting by red-tailed hawks was often adjecent to agricultural areas. Seidensticker and Reynolds (1971) found low levels of pesticide contamination and some eggshell thinning in red-tailed hawks in southcentral Montana, but they concluded that disturbance by man was more significant in causing nest failures than pesticides. The number of nesting pairs of red-tailed hawks was estimated to be about 57 pairs. This yields a nesting density of 1.2 pairs per 100 sq km for the study area. SWAINSON'S HAWK (Buteo swainsoni) The Swainson's hawk was a common nesting species on the study area. The breeding population was migratory, being present on the study area from April through September. 24 Nesting Swainson's hawks were associated with riparian habitat in the eastern half of the study area. Thirty-two nests (including alternates) were located in or adjacent to the study area during the study. All Swainson's hawk nests were in deciduous trees or shrubs (Table 2), with cottonwood used most frequently (69%). Trees and shrubs used for nesting by Swainson's hawks tended to be smaller (average height = 6.2 m) than those used by nesting red-tailed hawks (average height= 10.6 m) . Swainson's hawk nest heights were also lower than red-tailed nest heights, but the two species build their nests at about the same level within the nest trees (percent height equals nest height divided by substrate height times 100 = 71% for red-tailed hawks and 74% for Swainson's hawks). Gilmer et al. (1983) and Schmutz et al. (1980) both reported that Swainson's hawk nest heights were lower than red-tailed hawk nest sites. Nest elevations ranged from 1152 m to 1378 m (Appendix K) . Four nests (12%) were in shelterbelts at abandoned homestead sites, and the others were in native riparian vegetation in creek bottoms and coulees. Swainson's hawks also nested in shelter belts and creek bottoms in central North Dakota (Gilmer et al. 1983, Gaines and Kohn 1983), southeastern Alberta (Schmutz et al., 1980), and California (Bloom 1980) , but primarily nested in juniper in the Great Basin Desert of Utah (Smith and Murphy 1982b) . Riparian habitat only covers 4% of the study area, yet it was used by most of the nesting Swainson's hawks. It is possible that a few nests were overlooked in conifer scrub-savannah habitat, but sightings of Swainson's hawks did not indicate much use of this habitat. The number of young fledged per successful nest was 1.67 in 1982 (six nests), 2.11 in 1983 (nine nests), and 2.0 in 1984 (one nest). This compares favorably with 2.0 for southeastern Alberta (Schmutz et al. 1982) and 2.27 for California (Bloom 1980). Swainson's hawks were later in nesting phenology than other raptor species on the study area (Table 4) . Schmutz et al. (1982) found that Swainson's hawks were more susceptible to reduced fledging success than red-tailed hawks or ferruginous hawks when food shortages occurred, because Swainson's hawk young fledged when the ground squirrel population was past its peak and declining. Ferruginous hawk and red-tailed hawk fledging coincided with the peak of the ground squirrel population. Swainson's hawks fed on a wide variety of small birds and mammals (Appendix I) . An insufficient sample of prey items precluded calculations of percentages, so only the occurrence of prey in the diet is noted. Schmutz et al. (1982) calculated the dietary overlap (based on biomass) between Swainson's hawks and ferruginous hawks to be 82% and 98% for the two years of study. Gilmer et al. (1983) reported a 40% dietary overlap between Swainson's hawks and red-tailed hawks, based on percentage of occurrence. 25 The number of nesting pairs of Swainson's hawks was estimated to be about 45 pairs. This yields a nesting density of 1.0 pairs per 100 sq km for the study area. FERRUGINOUS HAWK (Buteo regalis) The ferruginous hawk was an uncommon summer resident in the grasslands of the eastern half of the study area. The breeding population was migratory, being present on the study area from April through September. Thirty-three nests were found in the study area, most of which were alternate nests for about ten breeding pairs. Nests were in clusters of up to nine nests in the same area. Seven nests (21%) were on small sandstone cliffs, and the remainder were on the ground, usually on steep, eroded hillsides (Table 2) . Nest elevations (Appendix L) ranged from 1225 m to 1414 m (mean = 1301 m) . Most nests faced north or west (Figure 4) . 12% NW 39% N 3% NE 21% E 6% Figure 4. Directional exposure of ferruginous hawk nests located along the Rocky Mountain Front, northcentral Montana, 1982 - 1984. All ferruginous hawk nests were originally built in grassland habitat. Most of the surrounding habitat around two nests was converted to dryland farming during 1982, when over 3000 acres (12.1 sq km) of native prairie were plowed. Neither nest was active in 1982 or 1983 . Although grasslands cover 47% of the study area, only areas with steep ridges or cliffs were used for nesting by ferruginous hawks. 26 Jasikoff (1982) concluded that ferruginous hawks avoid pure grassland areas with no trees. In most of the studies he cited, ferruginous hawks nested primarily in trees. On the East Front, large tracts of native grassland containing rugged topography (steep hillsides and ridges) were the primary requirements for the ferruginous hawk. Lokemoen and Duebbert (1976) found that ferruginous hawk nests were located farther away from human disturbance than randomly-selected points. Most of the nests on the East Front were located out of sight of roads or inhabited buildings . Fledging success was three young per successful nest in both 1982 (three nests) and 1983 (two nests) . Three nests failed in both 1982 and 1983. Production data were not obtained in 1984. The productivity of ferruginous hawks is thought to be related to prey abundance (Snow 1974a) . Nesting chronology is shown in Table 4. Prey remains from nests included ground squirrels and jackrabbits (Appendix I) . Ferruginous hawks have been reported to prey on a wide variety of mammals and birds, although their diet is generally less diverse than red-tailed hawks (Snow 1974a) . MERLIN (Falco columbarius) The merlin was a rare summer resident on the study area. Three nests were reported in the study area by Crenshaw (1979) and Wenzel (1982). One of the sites was apparently not used in 1982, although merlins were sighted about 2 km north of the nest site. They may have had an alternate nest site which was not located. This site fledged four young in 1983. Nesting was not confirmed at the other two sites during this study. An additional nest was found during 1984, which fledged three young. All four merlin nests were in abandoned black-billed magpie (Pica pica) nests, three in limber pines (Pinus f lexilus) , and one in cottonwood (Populus spp.) in riparian habitat. Ellis (1976) reported finding merlin nests only in conifer trees in northcentral Montana, but merlins nested in shelterbelts and riparian habitat on the Canadian prairies (Fox 1964, Hodson 1976). The presence of abandoned corvid nests is more important than the tree species (Trimble 1975) . The merlin is thought to be fairly rare in Montana, compared to other regions, and the population may be declining (Trimble 1975). The Richardson's merlin has suffered population declines over much of its range due to pesticides and habitat destruction (Fox 1971, Hodson 1976, Trimble 1975). Suitable nesting habitat for merlins in the study area (conifer savannah, riparian habitat, shelterbelts) appeared to be largely unoccupied by merlins. No population estimate was attempted for merlins because of the lack of data. 27 PRAIRIE FALCON (Falco mexicanus) The prairie falcon was a common nesting species in the study area. The breeding population nested mainly in the Sawtooth Range in the western half of the study area. Prairie falcons were rarely observed on the study area during winter. Prairie falcon aeries were difficult to locate due to the lack of a visible nest structure (Snow 1974b) and the large height and extent of the cliffs to be searched. Helicopter surveys were inefficient, detecting no more than half of the nesting pairs present on any given flight. Many hours of ground observation were usually required to locate aeries. Therefore emphasis was placed on determining occupancy of a cliff by prairie falcons rather than locating each aerie. Fifty-seven pairs of prairie falcons were found during the study, of which 55 were in the study area or within one km of the boundary, and two were about 8.8 km north of the study area boundary. It is estimated that only one-half to one-third of the prairie falcon pairs on the study area was found. All prairie falcon aeries were located on cliffs which ranged in height from 6 m to 183 m (mean =' 7 9 m) . Approximate nest elevations (Appendix M) ranged from 1244 m to 2317 m (mean = 1901 m) . Directional exposure of the 35 occupied cliffs is shown in Figure 5. The majority of cliffs faced northeast or east. Directional exposure of 54 occupied cliffs located within the study area boundary was compared to the exposure of available cliffs using the Chi-square test. East, northeast and southeast exposures were treated separately and all other exposure categories were lumped together due to small expected values (Hoel 1966) . The difference between prairie falcon nest cliff exposures and available cliff exposures was not significant (d.f.= 3, = 3.148, p = .30). Leedy (1972) also found that prairie falcons selected nest exposures on the basis of availability. 2% N 38% 3% w E 34% Figure 5. Directional exposure of prairie falcon nests located along the Rocky Mountain Front, northcentral Montana, 1982 - 1984. 28 The number of young fledged per successful nest (Table 3) was 3.2 in 1982 (five nests), 3.8 in 1983 (eight nests), and 4.5 in 1984 (two nests) . Other aeries were known to have fledged young, but accurate counts were not made. The contents of most aeries were not visible from either the ground or aircraft, so fledging counts usually could only be made after fledging had taken place. Fledged prairie falcons dispersed rather rapidly from the nest vicinity making accurate counts difficult to obtain. Two aeries were known to have failed in 1983 from unknown causes. Reoccupancy of nesting cliffs from year to year was high. Ten of eleven occupied cliffs from 1982 were occupied in 1983, and one cliff was not checked. Three cliffs have been occupied at least since 1975. Prairie falcons arrived at the nest sites starting in early March (Table 4). Egg-laying was initiated in April. Leedy (1972) reported a similar phenology for prairie falcons nesting in an area adjacent to the study area. Leedy (1972) compared pesticide levels and reproductive success in an area adjacent to the study area with two other regions in Montana. Prairie falcons in this area generally had lower pesticide contamination and higher reproduction rates than those in an area west of the Continental Divide. Prey remains noted at nests in the study area are listed in Appendix I . Prairie falcons are known to feed on a wide variety of birds and mammals, but usually prey heavily on the most abundant available prey (Becker 1982, U.S. D.I. Bureau of Land Management 1979, Leedy 1972, Porter and White 1973, Enderson 1964) . Various species of ground squirrels were key prey species for prairie falcons in most of the above-mentioned studies. Cliff habitat only covered 1% of the study area, yet was used by 100% of the prairie falcons for nesting. Linear distance is probably a more meaningful measure of cliff availability. Approximately 316 km of cliffs were available in the study area. This yields about 6.1 km of cliff per nesting pair (52 nesting pairs) . The prairie falcon population density (based on 30 known pairs) was about 1.1 pairs per 100 sq km or one pair per 90 sq km. PEREGRINE FALCON (Falco peregrinus) No peregrine falcons were observed during the study, although two sightings of migrating peregrines were reported by other observers (L. Young, pers. comm.; W. Elliot, pers. comm.). It is probable that the peregrine falcon nested in the study area prior to the population decline brought about by organochlorine pesticides. Enderson (1969) estimated the population in the northern Rocky Mountains to be less than one pair per 5,000 square miles in 1964 and 1965. 29 Within the arid western states, the peregrine falcon generally breeds near rivers or lakes where shorebird, waterfowl, and songbird populations tend to be high, and where prey is vulnerable to attack over water (Enderson 1969 , Porter and r,7hite 1973). Nelson (1969) speculated that reduced precipitation and higher temperatures since 1870 may have caused a small decline of peregrine populations by causing lower water levels in lakes and ponds, which reduced the populations of shorebirds. He felt this may have improved habitat conditions at higher elevations and above 50° north latitude. His theory remains conjectural. Snow (1972) reported that increasing development of the west had resulted in loss of habitat and lower peregrine populations. Neither climatic changes or habitat changes caused the large scale population declines. Organochlorine pesticides are believed to have been the major cause (Snow 1972, Ratcliffe 1980). As a result, large expanses of suitable habitat remain unoccupied, and habitat deterioration is not presently the major factor limiting peregrine populations (Snow 1972) . Peregrine populations in some areas have started to recover (Ratcliffe 1980) . Protection of suitable habitat is necessary to allow expansion of peregrine populations back into previously occupied areas . Peregrines tend to choose higher cliffs usually associated with lake or river (riparian) habitats, for nesting, and higher sites on the cliff than do prairie falcons (Porter and White 1973) , although nests have been found on small cliffs, steep river banks, and in hollow trees (Bent 1938). Several historic peregrine nests were located on steep banks along the Milk River in Montana (Flath, pers. comm.). Distances from aeries to hunting areas ranged from 0.31 km. to 15.6 km. in Utah (Porter and White 1973) . Bond (1946) reported that few peregrine nests were found above 1524 m (5000 ft.) elevation. In California, 11% of the cliffs occupied by peregrines were between 5000 and 5999 feet and none were above 6000 feet elevation (Boyce and White 1979) . The majority of peregrine aeries in Colorado were above 6000 feet (1829 m) and one was at an elevation of 12000 feet (Porter and White 1973) . There is little information on what factors may prevent peregrines from nesting above certain elevations, but Cade (Pers. comm.) thought that elevations suitable for nesting prairie falcons would probably be suitable for nesting peregrines. Ellis (1982) rated cliffs for suitability for nesting peregrines in Arizona on the basis of height, extent, surrounding habitat, distance to water, and prominence. Nearly all of the cliffs in the East Front study area would rate good to excellent under this system (DuBois 1983) . The cliffs on the East Front considered to be the best peregrine habitat were those which were close to extensive riparian habitat (within 5 km) , over 50 m in height and one km in extent, with numerous nesting ledges, and the majority of the cliff under 2300 m elevation. Cliffs meeting these requirements included the Castle Reef - Diversion Dam area, South 30 Fork Willow Creek, South Fork Teton Cliff, Wind Mountain, Muddy Creek and Blackleaf Creek Canyons, Rinker Creek, North and South Forks Dupuyer Creek, the northern portion of Walling Reef and Split Mountain areas, Heart Butte, Cutrock Creek, and the Dearborn River Canyon. 2. NOCTURNAL RAPTORS Six species of owls were observed on the study area during the study (Appendix G) : the great horned owl, short-eared owl (Asio f lammeus) , great gray owl (Strix nebulosa) , northern saw-whet owl (Aegolius acadicus) , western screech-owl (Otus kennicottii) , and eastern screech owl (Otus asio) . Four additional species have been reported by other observers: the snowy owl (Nyctea scandiaca) , burrowing owl (Athene cunicularia) , northern pygmy-owl (Glaucidium gnoma ) , and long-eared owl (Asio otus) . GREAT HORNED OWL (Bubo virginianus) The great horned owl was a common year- long resident in the study area. Eleven nests were located during the study. Two nests were on cliffs, eight were in deciduous trees or shrubs, and one was in an abandoned barn (Table 2) . Nine of the nests (the barn nest and tree nests) were abandoned corvid or buteo nests. Nest heights ranged from 2.1 m to 9.1 m (Appendix N) . Trampling by the young destroyed three of the nests by fledging time. Nero (1980) also reported this behavior for great gray owls. Fledging success (Table 3) was two young per successful nest in both 1982 (two nests), 1983 (eight nests), and 1984 (1 nest). One nest failed in the incubation stage in 1983, possibly due to a snowstorm. Great horned owls initiate nesting much earlier than other species of raptors (Table 4) . Most great horned owl nests were located in riparian habitat. Riparian habitat was present below both of the cliff nests, and approximately one km from the barn nest. It is likely that riparian habitat supported greater densities of prey species than other habitats. Two of the stick nests were believed to have been abandoned buteo nests, and the other six corvid nests. Gilmer et al. (1983) found that great horned owls in North Dakota used nests built by different species in proportion to their availability. The total number of pairs of great horned owls in the study area was at least 46. This yields a minimum density of 1.0 pairs per 100 sq km. The actual population of great horned owls was probably much higher than this. BARRED OWL (Strix varia) Two barred owl sightings were recorded for the study area. One was a road kill found near Bowmans Corners at the south edge of the study area (P.D. Skaar , pers. comm.). The other was a fall sighting of an adult bird near Gibson Reservoir (R. Escano, pers. comm.). Barred owls are probably only accidental east of the Continental Divide in Montana. No habitat in the study area was thought to be suitable for nesting barred owls. 31 C. GREAT HORNED OWL HOOTING SURVEYS The results of the great horned owl survey routes are shown in Table 5. The highest number of pairs were found on the conifer savannah route, however most of those pairs were actually in a riparian area which was adjacent to the conifer savannah habitat being sampled. It appears as though riparian habitat supported more owls than grassland or conifer forest habitat, although further testing would be necessary to determine actual differences between the habitats. The method has not yet been tested to determine reliability of response rates by great horned owls, however there are plans to do so (Youmans, pers. comm.). Table 5. Numbers of great horned owls detected along hooting survey routes in four habitats along the Rocky Mountain Front, northcentral Montana, 1983. NO. NO. PAIRS NO. PAIRS HABITAT PAIRS PER STOP PER KM Grassland 1 Conifer Savannah 7 Conifer Forest 2 Riparian 6 0.1 0.125 0.7 0.875 0.2 0.25 0.6 0.75 D. BALD EAGLE WINTER SURVEYS The bald eagle was present on the study area from September through April as an uncommon winter resident and migrant. The wintering bald eagle population was estimated to be about 15 birds on the Sun River near Augusta and five birds on the Teton River near Choteau during the winter of 1981-82. Few bald eagles were observed during the winters of 1982-83 and 1983-84, possibly due to weather factors and fewer hours of observation in the field. The 1983 mid-winter bald eagle survey for Montana showed a slight increase over 1982 (Flath 1983) .. The distribution of wintering bald eagles in the study area was influenced by the amount and location of open water. During extended periods of extreme cold, bald eagles were concentrated around the few areas of open water. At least two of these "core" wintering areas were located in the study area: 1) Elk Creek and the Sun River near Augusta and 2) the Teton River from Choteau to the Tetonview School west of Choteau. Other core wintering areas probably existed on the North Fork Dearborn River and possibly other drainages, but these areas were not searched during periods of cold weather. During mild weather, open water was widely available and bald eagles dispersed along all the major waterways. Other food sources utilized by bald eagles included carrion from road kills, big game winter ranges, and livestock operations; newly-emerging ground squirrels during early spring, and gut piles left by hunters during fall. 32 E. ROAD SURVEYS A total of 1142 raptors was sighted during 27546 km (17120 miles) driven. Three species (northern harrier, Swainson's hawk, and American kestrel) comprised over half the total sightings (Table 6) . The number of American kestrels per distance driven is an underestimation because kestrel sightings were not recorded during the first few months of the study. A total of 41.5 birds per 1000 km driven, and 18 species were recorded. This is less than half the number recorded by Woffinden and Murphy (1977) in the eastern Great Basin of Utah (100.2 birds/1000 km traveled), and Craig (1978) in southeastern Idaho (84.9 birds/1000 km traveled. Table 6. Relative abundance of raptor species observed while driving 27546 km along roads in the Rocky Mountain Front shady area, northcentral Montana, December 1981 - August 1984. NUMBER NUMBER PER NUMBER PER PERCENT SPECIES OBSERVED 1000 MILES DRIVEN 1000 KM DRIVEN ABUNDANCE N. Harrier 259 15.1 9.4 22.7 American Kestrel 181 10.6 6.6 15.8 Swainson's Hawk 176 10.3 6.4 15.4 Red-Tailed Hawk 175 10.2 6.4 15.3 Golden Eagle 162 9.5 5.9 14.2 Prairie Falcon 72 4.2 2.6 6.3 Ferruginous Hawk 36 2.1 1.3 3.2 Rough-Legged Hawk 20 1.2 0.7 1.8 Bald Eagle 18 1.2 0.7 1.6 Great Horned Owl 12 0.7 0.4 1.1 Sharp-Shinned Hawk 9 0.5 0.3 0.8 Cooper's Hawk 8 0.5 0.3 0.7 N. Goshawk 5 0.3 0.2 0.4 Short-eared Owl 3 0.2 0.1 0.3 Merlin 2 0.1 0.1 0.2 Osprey 2 0.1 0.1 0.2 Gyrf alcon 1 0.1 0.04 0.1 Turkey Vulture 1 0.1 0.04 0.1 TOTAL 1142 66.7 41.5 100 VI. DISCUSSION A. NESTING POPULATION DENSITY The number of nesting pairs on the study area was estimated for each species for comparison with other studies (Table 7). The estimates are based upon pairs which were encountered during the study and are probably considerably below the actual number present for most of the species. The total population was estimated to be about 446 pairs or 9.5 pairs per 100 sq km. A population estimate of the common raven (Corvus cor ax) was not attempted although they are ecologically classified as raptors 33 and are included in the population estimates of most of the other studies cited below. The nesting density of raptors on the East Front was slightly higher than average in comparison to other areas in several western states, but far below the exceptionally high densities found on the Birds of Prey Natural Area and the adjacent Grandview area of southern Idaho (Table 8) . Table 7. Estimated breeding densities for 18 species of raptors in tbe 4700 sq km Rocky Mountain Front study area, northcentral Montana, 1982 - 1984 (based upon active nests and sightings of territorial pairs) . SPECIES ESTIMATED NO. OF PAIRS NO. PAIRS PER 100 SQ KM NO. SQ KM PER PAIR PERCENT OF TOTAL PAIRS Northern Harrier 85 1.8 55 19. 1 American Kestrel 73 1.6 64 16.4 Red-tailed Hawk 57 1.2 82 12.8 Prairie Falcon 52 1.1 90 11.7 Great Horned Owl 46 1.0 102 10.3 Swa in s on ' s Hawk 45 1.0 104 10. 1 Golden Eagle 37 .8 127 8.3 Saw-whet Owl 15 .3 313 3.4 Ferruginous Hawk 10 .2 470 2.2 N. Goshawk 10 .2 470 2.2 Great Gray Owl 5 .1 940 1.1 Merlin 4 .1 1175 0.9 Short-eared Owl 2 .04 2350 0.4 W. Screech-owl 0.2 E. Screech-Owl 0.2 Pygmy Owl 0.2 Cooper's Hawk 0.2 Sharp-shinned Hawk 0.2 TOTAL 446 9.5 10.5 99.9 Table 8. Comparison of the nesting density of raptors in the Rocky Mountain Front study area, northcentral Montana, with areas in otber western states . STUDY AREA NO. PATRS LOCATION SIZE KM2 NO. PAIRS PER 100 km2 Rocky Mountain Front, Montana 4700 446 9.5 BPNA, Idaho (Howard et al. 1976) 135 294 217.8 Grandview, Idaho (Howard et al. 1976) 117 163 139.3 Southern Idaho (Howard et al. 1976) 12437 464 3.7 Hanford, Washington (Olendorff 1973) 1036 44 4.2 Pawnee, Colorado (Olendorff 1975) 2590 159 6.1 Cedar Valley, Utah (Smith and Murphy 1973) 207 35 16.9 Moose, Wyoming (Craighead and Mindell 1981) 31.1 24.7 79.3 Medicine Bow, Wyoming (Oakleaf, 1978) 3626 111 3. 1 TOTAL FOR ALL AREAS 24879. 1 1740.7 7.0 34 Newton (1979) stated that the distribution and density of raptors are dependent upon the distribution of nest sites and food. In most cases, raptor populations are limited by the number of suitable nest sites available (mainly cliffs or trees) . In the study area, the Sawtooth Range in the western half and the riparian areas and steep, eroded grassland ridges in the eastern half, provided most of the nesting habitat. Golden eagles and prairie falcons nesting in the Sawtooth Range were suspected to travel out onto the plains to hunt. Radio telemetry studies would be necessary to delineate foraging areas. B. IMPACTS OF MAN'S ACTIVITIES The primary human activities on the study area were livestock grazing, farming, logging, recreation, oil and gas exploration, and housing developments. Most of these activities were dispersed or too minor in extent to be detrimental to the raptor population. The most serious threat appeared to be the continuing conversion of native rangeland to dryland farming. During 1982, hundreds of acres of grasslands adjacent to a ferruginous hawk nesting area were plowed. Loss of habitat to dryland farming is one of the major threats to this species (Snow 1974a) . Housing developments may become a problem in the future. Present zoning laws do not take into account wildlife habitat. The Forest Plan for the Lewis and Clark National Forest (U.S.D.A. Forest Service 1982) called for increases in grazing and timber harvest levels. The levels of recreation and oil and gas exploration were also expected to increase. Increased road construction would be associated with all of these activities. Man's activities usually have the potential to impact raptors in one of the following ways: 1) direct mortality of individual birds (shooting, poisoning, electrocutions, etc.), 2) disturbance or pesticide contamination which results in lower productivity and recruitment, 3) elimination of nesting habitat, and 4) reduction of the prey base through poisoning or habitat destruction. Many authors have discussed the potential impacts of various types of disturbances and proposed general guidelines to protect raptors, but few have attempted to actually measure cause-effect relationships or the degree of protection needed (Suter and Jones 1981) . Raptors are difficult to study for disturbance impacts because they are very mobile, have large home-ranges, relatively low population densities, and reproductive rates which often fluctuate widely from year to year due to poorly understood factors (Ellis 1981, Newton 1979, Brown 1970) . 1. Direct Mortality Direct man-caused mortality did not appear to be a major problem on the Rocky Mountain Front. Electrocutions on power lines (golden eagles and great horned owls) and collisions with vehicles (short-eared owls) were the only types of man-caused mortality observed. These mortality factors did not appear to be limiting raptor populations on the Rocky Mountain Front. 35 2. Loss of productivity a. Pesticides Fledging success from successful nests was average, indicating no apparent problem from pesticide contamination. Ellis (1979) and Leedy (1972) found the levels of contamination in golden eagles and prairie falcons to be under the threshold necessary to cause a significant reduction in productivity. b. Disturbance Loss of productivity due to disturbance of nesting pairs was difficult to assess because the causes for most nest failures were unknown. The sample size of nests was too small for comparison of productivity of nests near human activities (such as roads and dwellings) with those far from human activities. Most oil and gas exploration during the study was conducted after most raptors had fledged. Abandonment of one prairie falcon aerie in 1981 was believed to have been caused by seismic exploration activities (L. Young, pers. comm.). A goshawk nest located along a trail on a dude ranch Was regularly disturbed by people on foot and horseback in 1983. The fledging success of one young was below the normal for goshawks, possibly due to disturbance. A ranch hand reported climbing up to a ferruginous hawk nest in 1983 and observing four eggs after the adult flushed. The nest fledged three young, and one unhatched egg remained intact in the nest after the young had fledged. This is in contrast to reports by many investigators of the extreme sensitivity of ferruginous hawks during incubation (Snow 1974a, Thurow et al. 19 80) . One golden eagle nest containing two downy young (3-4 weeks old) was observed while a surface charge seismic line was conducted past the nest. The nest was located 76 m high on a 122 m cliff overlooking the plains. The line was initiated 5 km from the nest and ran directly toward the nest in full view of it. The adult golden eagle flushed from the nest each time a charge was set off when the line approached to within 1.6 km of the nest. The adult often remained off the nest for extended periods of time, sometimes flying back and forth in front of the cliff, and sometimes flying out of sight toward the south. The adult eagles did not approach the nest once the blasting approached to within 0.8 km. Blasting progressed to a point directly below the nest, then resumed several hundred meters down from the top of the cliff on the backslope of the hogback, out of sight of the nest. Both adults appeared back at the nest shortly after the blasting started on the other side of the hogback, and they no longer flushed when a charge was set off (the sound was muffled significantly by the hogback). The weather was mild (16-23 °c with a high overcast) during the incident, reducing any danger to the young of exposure to extreme heat or cold. Ellis (1973) reported that nestling golden eagles suffered temporary weight 36 loss when the adults were kept away from the nest by the presence of observers. It is likely that death of the eggs or young would have occurred if the nest had been in the incubation or very early nestling stages. Impacts of the study Observer activities during the study may have had an impact on productivity, although every effort was made to minimize disturbance during data collection. Thurow et al. (1980) reported a significantly lower fledging rate for ferruginous hawk nests which were disturbed experimentally (approached until the adults left the nest) than nests which were not disturbed. During this study, the reactions of nesting raptors to observer approach varied with the raptor species, stage of the nesting season, and method of approach (helicopter, supercub or ground). Reactions of raptors were not quantified due to small sample sizes of observations. Ground Surveys Most raptor species were more alarmed by ground approaches (especially on foot) than by aircraft. This is similar to the findings of White and Sherrod (1973) . Prairie falcons showed the least response to ground approaches mainly due to the great height above the ground of most aeries. Prairie falcons showed greater alarm when observer approaches were made from the tops of the cliffs, than from below. Swainson's hawks usually allowed the observer to approach more closely during incubation than while young were in the nest. The few incubating birds which were flushed flew away, while birds with nestlings vigorously defended the nest by stooping and screaming. Fixed Wing Aircraft Surveys Close approaches to nests with a supercub never caused golden eagles or buteos (red-tailed hawk, Swainson's hawk, ferruginous hawk) to flush from the nest. Incubating or brooding adults maintained brooding posture, and adults with young usually covered the young by spreading their wings over them. Prairie falcons occasionally flushed from the cliff and circled around near the airplane. i Helicopter Surveys Close approaches by helicopter (to within 15m) rarely caused buteos to flush. Golden eagles never moved from brooding posture or flushed from the nest in spite of being buffeted by strong wind currents from the rotor blades. Prairie falcons often flushed ahead of the helicopter and circled in alarm. They were more easily flushed from the cliff with the helicopter, than with the supercub. Most prairie falcon aeries were in deep crevices or potholes, so behavior of brooding adults or nestlings was rarely observed. One female was observed to flush from an aerie with four eggs (the only aerie which could be looked into 37 from a helicopter) , and another sat in the entrance of the pothole aerie and watched the helicopter go by. The response of prairie falcon nestlings to the helicopter was to flee into the back of the aerie, while golden eagle nestlings always remained stationary. Active raptor nests were exposed to close aircraft approaches a maximum of three times (usually twice) during the nesting season. No nest abandonment due to aircraft approaches was suspected. Raptors probably have a threshold of tolerance to disturbance which, when exceeded, will result in nest abandonment or significantly lower productivity. Some raptors may become conditioned to disturbance, successfully fledging young in spite of high levels of stimuli (Ellis 1981) . Others may become sensitized to disturbance, flushing at greater distances with each additional approach (Thurow et al. 1980). 3. Elimination of Nesting Habitat Loss of nesting habitat will cause a decline in raptor populations if nesting habitat is limiting (Newton 1979) . Declines associated with habitat loss can only be documented with long-term population studies. Craighead and Mindell (1981) attributed a 30 percent decrease in 28 years in the raptor population near Moose, Wyoming to a combination of habitat loss and increasing human disturbance. Habitat loss contributed to lower merlin populations near Kindersley, Saskatchewan (Hodson 1976) . Cliffs, conifer forests, and riparian zones were the most commonly used habitats for nesting by most raptor species on the Rocky Mountain Front, yet collectively they covered only fifteen percent of the study area. Ninety-eight pairs of raptors were found to use cliffs for nesting (golden eagle - 35, prairie falcon - 52, red-tailed hawk - 4, ferruginous hawk - 4, great horned owl - 2, and American kestrel - 1) , resulting in a total density of 31 pairs per 100 km of cliff or 3.2 km per pair. Clearly, development causing loss of these habitats would have a much greater impact than development causing the loss of an equal amount of grassland or conifer savannah habitat. Riparian habitat on the Front has already suffered loss due to severe floods in 1964 and 1975, construction of two major water-storage reservoirs, and private home construction. Timber harvest could decrease conifer forest habitat suitable for goshawks if a greater than sustained yield is harvested, or a short rotation period is employed (which would decrease the amount of old-growth forest) . Cliff habitat by itself is nearly immune to destruction, but adjacent disturbance could render them unsuitable for raptor nesting. Developments close to cliffs were responsible for the loss of several peregrine falcon nest sites in Utah (Porter and White 1973) . Some nesting habitat has increased as a result of human activities. Shelterbelts were utilized for nesting by Swstinson's hawks and great horned owls. Establishment and maintenance of additional shelterbelts could increase nesting habitat for these two species and possibly the red-tailed hawk. 38 4. Reduction of Prey Base Reduction of the prey base through poisoning or habitat alteration such as grazing could cause a decline in a raptor population if the food supply is the limiting factor or the population (Newton 1979) . Conversion of large areas of native grasslands to dryland crops or monotypic grasses is believed to have caused declines of ferruginous hawks by decreasing populations of jackrabbits (Snow 1974a, Howard and Wolfe 1976) . Conversion of grassland to croplands is one of the major habitat changes presently occurring on the study area. The impact on prey species is impossible to determine without conducting extensive prey-base studies. 5. Cumulative Impacts Combinations of impacts can interact to exert a greater cumulative impact on raptor populations than the sum of the impacts alone. Ferruginous hawks under stress from a decline of the prey base were less tolerant of disturbance, flushing at greater distances and abandoning their nests more readily than hawks with a good food supply (Thurow et al. 1980). The highly interspersed public, state, and private lands on the Rocky Mountain Front could increase the likelihood of several different tfpes of developments taking place without regard for cumulative impacts . VII. Management Recommendations $ ~ The goals of raptor management on the Rocky Mountain Front should bPTd*fv X C LU 1 A pCLUlA x \j \J J~ UI1I VJ CL 11 v xa x FTPTnonli^ 1a alnestris Is X w 1 11 \J VJ 1 1 JL -L. CI CI 1 L/ w O %- -L J- O x Pica Dica x Tnrdus mi pratorius x TJni dent i f 1 pd ^tiflrrow U *. 1 J- VI II U i- 1 1CU J-» CI X X w W x Sturnella neglecta X X X X Unidentified blackbird X X Unidentified bird X Sylvilag'-s spp. X Lepus tovnsendii X X X Marmota flaviventris X Spermophilus richardsonii X X X Spermophilus columbianus X X Spermophilus spp. X X Thomomys talpoides X Peromyscus maniculatus X Microtus spp. X X 109 Appendix I. (continued) Raptor Species Golden Swainson's Ferruginous Prairie Great Horned Prey Species Eagle Hawk Hawk Falcon Owl Ondatra zibethicus X Mustela nivalis X Odocoileus hemionus (fawn) X Unidentified snake X X Catostomus spp. X Crayfish X Grasshopper X X Beetle X 110 Appendix J. Nest-site characteristics of red-tailed hawk nests located along the Rocky Mountain Front, northcentral Montana, 1982 - 1984. Nhb I N fc,b 1 ItPTfHT riEiUjiil rn.KL.CiN I bUKKUUND Lf NU . bUrrUKl bUrrUKl \wi) Nr.ol im/ UJ?T PUT E.L.E.VA11UN \m) rvonci id it UAOTTAT HAd 1 1 A 1 i L Populus spp . Q 1 7.1 A 1 0.1 0 / 1 0ft7 1 Zo / Riparian Z (-11 ff L. X X 1 1 O 1 y . i A 1 0.1 A7 0 / 1 9Q 7 1 Ztt / l\ r. Crass land J Populus spp. Q 1 y . I A 1 0.1 A7 0 / 1 Z JZ Riparian 4 Populus spp. 10 0 1 Z . Z Q 1 y . i 7 c 1 9A8 1 ZOO Riparian c D Populus spp. 1U . / 4.0 4 J 1 0 OO i zyy Riparian 0 Populus spp. 0.1 A Q ^ . y on oil 1 OQ1 i zy j Riparian 7 / Populus spp. Q 1 V • 1 7 A / . 0 oo OJ 1 97/. 1 Z / 4 Riparian Q o Populus spp. 0.1 7 c 1 /. 0 7 14Z / Riparian y Populus spp. in 7 10. / 7 £ / . 0 7 1 / 1 1 0A9 1 ZOZ Riparian i n 10 Populus spp. A 1 0. 1 4.0 7 c 19 7/. 1 Z / 4 Riparian 1 1 Populus spp. in 7 10. 7 7 £. / . 6 7 1 /I lzoO Riparian 12 Populus spp. 7 . 6 C 1 6. 1 80 1 OAC 1305 Riparian 13 Populus spp. 10. 7 7 r 7.6 7 1 71 1250 Riparian 1 /. Populus spp. in 7 10. / 7 A / . 0 7 1 / 1 i on i 1 Z0 1 Riparian ID Populus spp. 1 J . Z 117 Ij. / Oft yu 1 OCA 1 ZDU Riparian ID Populus spp. 1 n 7 10 . / O 1 y . i CO 1 £ 1 & 1010 IN Hi Conifer 17 Cliff 9.1 6.1 67 1829 S Conifer S avannah 18 Cliff 30.5 7.6 25 1463 E Conifer Savannah 19 Populus spp. 13.7 12.2 89 1311 Riparian 20 Cliff 4.6 3.0 67 1366 NW Grassland MEAN = 10.6 7.1 71.0 1338.7 SD = 5.36 2.56 14.95 148.85 RANGE = 4.6-30.5 3.0-13.7 25-90 1201-1829 -4 Ill Appendix K. Nest-site characteristics of Swainson's hawk nests located along the Rocky Mountain Front, northcentral Montana, 1982 - 1984. NEST NEST TTT7 T /1TT*"P HEIGHT HEIGHT PERCENT ELEVATION SURROUNDING NO. SUPPORT SUPPORT (m) NEST (m) HEIGHT EXPOSURE TT A T» T rp A T> HABITAT la Populus spp. "7 C 1 . 6 6. 1 oO lion Grassland lb Populus spp. 2 . 4 1 . 8 75 1201 Grassland 2 Salix spp. 2.7 2. 1 78 1378 Riparian 3 Prunus spp. 4 . 6 3.0 67 ion 1317 Riparian 4a Populus spp. £ 1 6. 1 3. 0 50 1 1 1 o 1323 Grassland 4b Fraxinus spp. 4.6 3.0 67 1 O O 1 1323 Grassland 5 Prunus spp. 3.0 2.4 80 1 O "7 O 1378 NW Grassland 6 Populus spp. 9. 1 7 . 6 83 1 i o o 1 183 Riparian 7 Salix spp. f o r f 1250 Riparian 8 Salix spp. *5 "7 3. 7 3.0 83 1305 Riparian ^ 9 Populus spp. 3. 0 1 O 1 . 8 60 1207 Riparian 10 Populus spp. C 1 6 . 1 4 . b -7 C 75 123/ Riparian 1 1 Populus spp. n i 9. 1 8. 2 90 1 O 1 A 1219 Riparian iZ Populus spp. b . 1 c c J . J yu 1 1 "7 1 1 I / 1 Riparian 1 J Populus spp. h . b "3 1 J . J "7 "i 1 1 en 1 1_)Z Riparian Populus spp. in "7 O 1 y . i ob 1 1 o o lZ Jo Riparian 1 r ID Populus spp. y . l b. 1 b7 lzzb Riparian lb Populus spp. 4 . b J . 7 o0 1 o c o lzbo Riparian 1 / Populus spp. I Z . Z n i y . i 75 1219 Riparian 1 Q io Populus spp. in -t 10 . / b . 1 57 1 1 "7 1 1171 Riparian 19 Populus spp. 6. 1 4. 6 75 IOC/* 1256 Riparian Zl) Populus spp. O 1 "7 £. oj 1 1 £ O 12o2 Riparian Z I Populus spp. 9. 1 b . 1 £ "7 67 1 1 o t\ 1 189 Grassland ZZ Salix spp. Z . 4 z . 1 Q"7 O / i i ~i i 11// Riparian 23 Prunus spp. 1.8 1.8 100 1335 Riparian Z4 Populus spp. / . b ^ i b . 1 80 1 1 "7 "7 1177 Riparian 25 Populus spp. 9.1 7.6 83 1165 Riparian 26 Prunus spp. 3.0 1.8 60 1360 Grassland 27 Populus spp. ? 1238 Riparian 28 Prunus spp. 2.4 1.5 62 1335 Agricultural 29 Prunus spp. 3.0 1.8 60 1311 Riparian 30 Populus spp. 13.7 7.3 53 1378 N Grassland MEAN = 6.2 4.6 74.2 1254.2 SD .= 3.32 2.48 12.07 71.12 RANGE = 1.8-13.7 1.5-9.1 53-100 1152-1378 112 Appendix L. Nest-site characteristics of feruginous hawk nests located along the Rocky Mountain Front, northcentral Montana, 1982 - 1984. NEST NEST HL J.GH1 nr, IGH1 r CjKLeiN 1 _L.fc.VAl 1UN C TTTJT3 AITKTTA TMA SUKKOUNI) I NO NO. bUrrUKI DUrFUKl \m) Nr,bl \m) TJ T? T OUT (m) I?V"D AO TTD T? 1IADTTAT 1 LAd J 1 A I la Ground 1 1 1 "7 1 Ji / T T W Grassland lb Ground 1 11 Q T.T W Grassland 1 lc Ground 1 /. 1 /. c b Grassland Id Ground 1 O ft o 1292 •re E _____ T __ ___ J Grassland 2a Ground 1250 T.T W Agricul tural 2b Ground 1/5U T7 w Agricultural 3a Ground 1402 XT N Grassland 3b Ground 1 O "7 O 1 J 11 re fc. Grassland 4a Cliff 4.6 L A 4.0 87 1 O C A 1250 NW __ _ __ _ "1 __ __ J Grassland 4b Cliff 4 . 6 4.0 O "7 1 O C A 1250 XTT 7 NW Grassland 4c Cliff 4.6 4.0 87 1 O C A 1250 w Grassland 5 Cliff <_! 1 6. 1 _ "7 3.7 r a 60 TO// 1244 XT N Grassland 6 Cliff 1 A 3.0 3.0 1 AA 100 1384 sw Grassland —j __ 7a Ground 1 O O *7 1 237 c b Grassland 7b Ground ion 1_ 51 XT N Grassland oa Ground 1Z_5 IN Grassland ob Ground 1 0 0 ^ 1 ZZ5 XT N Grassland OC Ground 1 TIC IN urassiana n 9 Ground 1 0.79 1 J /Z C urassiauu l(Ja Ground 1 j/i w Grassland 1 AT. 10b Ground 1111 1J1 1 N Grassland 10c Ground 10 11 1 Jl 1 0 b Grassland lOd Ground 1111 1311 XT N Grassland i a 10e Ground 1111 1311 XT N Grass land lOf Ground 1011 1311 XT N Grassland lOg Ground 1 0 /. 1 1 J41 c b Grassland lOh Ground 1 0 /. 1 1341 XTT.T NW Grassland lOi Ground 1372 W Grassland 11 Cliff 2.7 2.1 78 1304 N Grassland 12 Cliff 3.0 2.4 80 1280 NW Crassland 13a Ground 1341 N Grassland 13b Ground 1341 N Grassland 14 Ground 1390 NE Grassland MEAN = 1307.9 SD = 57.71 RANGE = 1225-1414 113 Appendix M. Nest-site characteristics of prairie falcon nests located along the Rocky Mountain Front, northcentral Montana, 1982 - 1984. HEIGHT HEIGHT PERCENT ELEVATION SURROUNDING SUPPORT (m) NEST (m) HEIGHT (m) EXPOSURE HABITAT 1 76 72 95 1634 E Conifer Savannah 2 91 61 67 1646 NE Conifer Forest 3 61 ? ? 2158 W Conifer Savannah 4 122 91 75 1585 SE Conifer Savannah 5 61 9 15 1549 E Riparian 6a 122 98 80 1817 NE Conifer Forest 6b 152 114 75 1817 NE Conifer Forest 7a 46 12 26 1890 SW Conifer Savannah 7b 49 26 53 1805 SE Conifer Savannah 8 122 61 50 1829 NE Conifer Forest 9 46 23 50 1683 E Conifer Savannah 10 122 76 62 2158 E Conifer Forest 11 183 91 50 1817 S Conifer Savannah 12 30 9 30 1707 N Conifer Savannah 13 122 91 75 1890 NE Conifer Savannah 14 91 76 84 1951 SE Conifer Forest 15 30 18 60 2030 E Conifer Savannah 16 61 15 25 1921 NE Conifer Savannah 17 30 18 60 1646 NE Conifer Savannah 18 46 27 59 1854 NE Conifer Savannah 19 61 43 70 1921 NE Conifer Forest 20 76 64 84 1890 NE Conifer Savannah 21 30 15 50 1905 E Conifer Forest 22 152 107 70 1951 E Conifer Savannah 23 61 ? 1 2012 NE Conifer Forest 24 91 1 1 2317 NE Conifer Savannah 25 122 ? 1 2134 E Conifer Savannah 26 183 ? 1 2195 SE Conifer Savannah 27 152 76 50 2317 NE Conifer Savannah 28 91 61 67 1768 E Riparian 29 46 ? ? 2165 E Conifer Savannah 30 106 91 86 1890 NE Conifer Forest 31 122 61 50 1829 NE Conifer Savannah 32 183 152 83 1707 SW Conifer Savannah 33 122 91 75 2030 NE Conifer Forest 34 61 ? 1 2043 SE Conifer Savannah 35 6 5 83 1244 W Grass land 36 9 7.6 83 1805 E Conifer Savannah 37 24 12 50 2122 E Conifer Savannah 38 76 67 88 1555 E Conifer Savannah 39 61 30 50 1573 E ConifpT* SflVfrnriflh \J \J 1H.-L C i I > CL V d 1 L 1 L CL 1 L 40 152 ? 1 2268 E ConifpT" Savamiah • — \J 111 L t- i_ U CL V CL L L L L CI t 1 41 182 1 1 2134 NE Conif pt Sflv£tnnpb CL LJ CL V CL LLL L CLL L 42 61 1 1 2232 NE ConifpT Sflv^mnab \J \J LL J~ J- » — J. 1 — ' CI V all L LCL L L 43 9 3 33 1793 SE nonifpT Rpvflrmflh lJ CL V C11J-11-CJ1J. 44 30 ? 1 1829 NE Conifer Savannah 45 76 46 60 1951 SE Conifer Savannah 46 61 46 75 1921 NE Conifer Savannah 47 24 12 50 1573 SE Conifer Savannah 48 122 15 12 2195 SE Conifer Savannah 49 46 40 87 1695 NE Conifer Forest 114 Appendix M. (continued) HEIGHT HEIGHT PERCENT ELEVATION SUPPORT (m) NEST (m) HEIGHT (m) SURROUNDING EXPOSURE HABITAT 50 51 52 53 54 55 56 37 46 12 91 46 30 61 24 ? ? 1 1 1 ? 67 ? ? ? ? ? ? 1787 1915 1677 2226 2226 2043 1841 NW E NE E E E E Conifer Conifer Conifer Conifer Conifer Conifer Conifer Savannah Forest Savannah Savannah Savannah Savannah Savannah MEAN SD RANGE 79.0 48.86 6-183 50.2 36.90 3-152 61.3 20.76 1897.7 227.06 12-95 1244-2317 115 Appendix N. Nest-site characteristics of great horned owl nests located along the Rocky Mountain Front, northcentral Montana, 1982 - 1984. NEST NEST. HEIGHT HEIGHT PERCENT ELEVATION SURROUNDING NO. SUPPORT SUPPORT (m) NEST (m) HEIGHT (m) EXPOSURE HABITAT 1 Cliff 6. 1 2. 1 35 1280 S Grassland 2 Abandoned 4.6 2.7 60 1183 Grassl and Barn 3 Prunus 3.0 2.4 80 1372 NE Grassland 4 Cliff 3.0 2.1 70 1427 NE Grassland 5 Populus 9. 1 4.6 50 1396 Riparian 6 Populus 12.2 9.1 75 1396 Riparian 7 Fraxinus 4.6 3.4 73 1293 Grassland 8 Populus 9.1 9 ? 1274 Riparian 9 Populus 9.1 ? 1 1256 Riparian 10 Populus 9.1 6.1 67 1195 Riparian 11 Populus 13.7 7.6 56 1317 Riparian X = 7.6 4.5 62.9 1308.1 SD = 3.60 2.59 14.18 81.91 RANGE = 3.0-13.7 2.1-9.1 35-80 1183-1427 116 I