INTRODUCTION

Peregrine Falcon standing on its prey, a pigeon; Jones Beach St. Pk., LI, NY; Feb. About the photographs

Figure 1. Distribution of the Peregrine Falcon in North and Middle America and the western West Indies. This species also breeds in South America and locally worldwide. American birds winter from the dashed line south throughout the U.S. (except the Great Basin, Great Plains and Appalachians), Middle America, the West Indies, and South America. See text for details.

Peregrine Falcom juvenile on a Swallow box; Jamaica Bay WR, Queens, NY; Feb. One of the most widely distributed of warm-blooded terrestrial vertebrates, the Peregrine Falcon occurs from the tundra to the Tropics, from wetlands to deserts, from maritime islands to continental forests, and from featureless plains to mountain crags—it is absent as a breeder only from the Amazon Basin, the Sahara Desert, most of the steppes of central and eastern Asia, and Antarctica. This depth and breadth of habitat reflects a prodigiously catholic diet that includes many hundreds of species of birds, some bats, and a few rodents, and yet a commonality of ways in which Peregrines pursue them. The presence of this species in the pristine landscape has no doubt influenced the morphological and behavioral evolution of countless avian species. Even so, some populations of Peregrines are food specialists; in the Pacific Northwest, for example, enormous numbers of a few marine bird species support one of the densest-known Peregrine populations. The often-held image of the Peregrine as a symbol of wilderness diminishes when one sees this falcon breeding on metropolitan bridges and urban skyscrapers or watches tundra migrants on their neotropical nonbreeding grounds speeding along traffic-jammed boulevards at streetlight height in Rio de Janeiro, Brazil, or Buenos Aires, Argentina, chasing bats at sunset. Indeed, a Peregrine is always worth watching; humankind has long admired this species as nature’s perfect aerodynamic performer and as a strikingly beautiful bird. Few other North American species held as high a scientific and public profile in the twentieth century. Among the most studied of wild avian species, with a bibliography exceeding 2,000 primary scientific titles, the Peregrine was a cause célèbre of the environmental awakening of the 1970s. Ironically, its popularity increased with its disappearance as a breeding species from most of eastern North America and parts of Europe and its marked reduction over most of the rest of North America, Europe, and (probably) northern Asia. Although it was thought in many circles to be a globally declining and endangered species, this was never so. The Peregrine was, however, greatly harmed, along with other birds of prey and some marine birds, by the widespread use of persistent chemicals that lowered reproduction and survival rates. By 1970, the Peregrine was federally protected in the United States, and the chemical culprits were virtually banned in North America by 1972. Peregrines have since made a strong recovery, aided in part by restorative management. The name Peregrine means “wanderer,” and northern-nesting Peregrines are among North America’s long-distance migratory species, some moving 25,000 kilometers annually. It is difficult to characterize the resident status of the Peregrine as a species. While most spend but a few months over the northern third of their North American breeding range, some populations remain sedentary; for example, mated pairs can be seen sitting together on their snow-covered breeding ledges in January in the Aleutian Islands. Although most North American Peregrines used to nest on cliffs, their establishment as urban denizens over the past 2 decades (Frank 1994, Cade et al. 1996) has been dramatic and highly publicized in the popular press. Increasingly, they use other unconventional nest sites such as old Common Raven (Corvus corax) nests on electric pylons, Osprey (Pandion haliaetus) and cormorant (Phalacrocorax spp.) nests on channel buoys, abandoned Bald Eagle (Haliaeetus leucocephalus) nests along the Pacific Coast, an emergent dead tree snag in California, and special towers in salt marshes. Recently they have even extended their nesting range to such an unexpected location as Cuba (Regalado and Cables 2000). top

DISTINGUISHING CHARACTERISTICS

Peregrine Falcon in flight; Cape May, NJ; Oct. Medium to large falcon ( View Video). Total length: male 36–49 cm, female 45–58 cm. Adult with bluish-gray upperparts (becoming more blackish on head), variable-width blackish facial stripe extending down from eye across malar (“malar stripe,” used here, or “moustache” of some authors), this stripe usually set off by pale auriculars or “cheek,” but pattern sometimes obscured if cheek all dark; underparts whitish, grayish, or buffy with variable amount of blackish spotting and barring; under wing and under tail surfaces barred pale gray and black. Immature similar but upperparts vary from pale to slate or chocolate brown and underparts buffy with blackish streaks (vs. bars). Sexes best distinguished by size, with female 15–20% larger and 40–50% heavier than male; normally no size overlap between sexes within a given subspecies. Female also more heavily marked below (e.g., broader and fewer bars) on average than male (see Appearance and Measurements and Appendix 2). No seasonal variation in plumage other than muted or lessening of colors as feathers wear, but bare parts of male brighter in breeding season. Among large North American falcons, female Aplomado Falcon (Falco femoralis) is nearly the size of male Peregrine, but not stocky, heavy-looking, and more kestrel-like with long tail. Peregrine more easily confused with Gyrfalcon (Falco rusticolus) and Prairie Falcon (Falco mexicanus). Distinguished from Gyrfalcon by generally smaller size, wings narrower at base and more pointed, comparatively less rounded at tip (primary tip formula 9 > 10 > 8 > 7, in Gyrfalcon 9 > 8 > 10 > 7), shorter, less tapered tail; when perched, wing-tips reach nearly to end of tail (wing-tips do not reach tail tip in Gyrfalcon). Adult Peregrines usually have more contrasting dorsal-to-ventral colors, under wings not 2-toned, and cheek with more defined malar-stripe (entire cheek may be black, lacking pale auricular, in some). Immature Peregrine of race F. p. pealei most easily confused with Gyrfalcon, but proportions, especially wing shape, different. Distinguished from Prairie Falcon by being generally darker, less pale brown (Prairie Falcon “sandy” in color; however, many immature F. p. tundrius and some immature w. anatum also pale), more contrastingly patterned dorsal to ventral, proportionately shorter tail, and lacking the Prairie Falcon’s contrasting dark center of under wing (broadest in axillaries) seen in flight. Peregrine also has deeper, more fluid, and less stiff wing-beat than Prairie Falcon (Clark and Wheeler 1987, Dunne et al. 1988). Hybrid falcons bred for falconry (e.g., Peregrine Falcon * Prairie Falcon, Peregrine Falcon * Gyrfalcon, and various backcross mixtures [difficult to characterize]) sometimes lost to the wild and are readily confused with Peregrines (see Conservation and management, below).

DISTRIBUTION THE AMERICAS | OUTSIDE THE AMERICAS | HISTORICAL CHANGES | FOSSIL HISTORY

THE AMERICAS Breeding range Figure 1. Formerly extirpated from much of original range by synthetic organic chemicals such as DDT (see below and Conservation and management, below); reoccupancy and restoration still incomplete in 2001, especially in central and s. Canada and midwestern and e. U.S., where much of distribution is urban, but progressing rapidly (Enderson et al. 1995a). Thus, distribution as given is subject to change. Following information as of 2000–2001, provided by federal, provincial, and state agencies, recovery-team members, and individuals documenting recovery. Alaska, Canada, and Greenland. In the west from w. Aleutian Is. (Attu 53°N, 172°35’E) east through Aleutians and Alaska Peninsula, then north along coastal w. Alaska, where spotty but with local concentrations such as Norton Sound (64°N; absent from Nunivak, St. Matthew, Pribilof, St. Lawrence, and Diomede Is.), to North Slope of Alaska (about 70°N; locally, largely riverine, but moving into coastal plain around lakes north of 70°; R. Ritchie pers. comm.); Yukon Territory, Northwest Territories, and Nunavut locally north to about 73°30'–74°N in parts of Banks I., Victoria I., Melville I. to 75°N; Bothia Peninsula to about 72°N, to Baffin I. and then to ice-free parts of w. Greenland from Thule (Qaanaaq), about 76–77°N (scarce; Burnham 1996) south around tip and north on east side at least to Angmagssalik (65°40’N), although seen as high as Thomsen Land (75°N) and Germania Land (76°50'–77°N; Boertmann 1994), in breeding season. Then southward through Alaska, Yukon (spotty and local), Northwest Territories, Nunavut, British Columbia (poorly documented inland), n. and central Alberta, Saskatchewan (Saskatoon and Regina, where urban breeders), Manitoba (Winnipeg and Brandon; urban sites), s. Ontario (e.g., along Great Lakes), s. Quebec (along St. Lawrence River), Labrador (mainly coastal; Todd 1963; Canadian Wildlife Service 1988; G. Chilton, G. A. Court, U. Ban-asch, G. Holroyd pers. comm.). Absent as breeder from Newfoundland. United States. Locally (see Fig. 1) through northern tier of states, most midwestern and eastern states. Many introduced into urban areas (e.g., Milwaukee, WI; Chicago, IL; Fort Wayne, IN; New York, NY); spotty and local (urban) in midwestern states (e.g., Nebraska, Missouri, Iowa); spotty and local in most eastern states (e.g., New England, Pennsylvania, New York, New Jersey, Maryland, Delaware, Virginia, N. Carolina, S. Carolina, Alabama; Burnham 1995; J. Castrale, M. Amaral, C. Koppie pers. comm.). Widely in western states (e.g., most of Utah, Arizona, w. Colorado, w. and n. California; see Fig. 1), but absent from N. Dakota (although bred in urban Fargo, ND, in 2001; B. Tordoff pers. comm.), Florida, Oklahoma, Arkansas, Alabama, Mississippi, Louisiana, Texas (except sw. Rio Grande region), and Nevada (except along borders with Utah, California, and Arizona; Burnham 1995, TJC, CMW, WGH). Mexico. Baja California and islands of Gulf of California (absent from Guadalupe I.) and Sierra Madre Occidental and Oriental in Sonora, Chihuahua, w. Coahuila (locally), Durango (but poorly defined); south to near Ciudad Victoria, Tamaulipas (23°44’N; W. Wimsatt in Hickey 1969, Porter et al. 1988, D. Lan-ning pers. comm., WGH); perhaps at latitude of s. San Luis Potosí on Mexican Plateau (22°30’N; R. Munro-Wilson pers. comm.). Middle America and Caribbean. Extralimital nesting in 1999 confirmed for Holguín Province of e. Cuba (Regalado and Cables 2000) and one record given for Dominica (details unavailable; Raffaele et al. 1988). A mid-twentieth–century record suggested for cliff on Lago de Managua, Nicaragua (M. W. Nelson pers. comm.). Southern subspecies cassini over most of South America but absent as breeder from Central America, most of Amazon and Orinoco River basins. Winter range Nearctic. Northern limits of range ( Fig. 1) variable between coasts, more northward (except for Greenland) on west coast, throughout Aleutian Is. and Gulf of Alaska (Kodiak I.); on east coast north to Gaspé Peninsula, limit of range apparently function of urban locations with good prey populations or areas of abundant prey (e.g., open water or edge of ice sheet); seemingly shifted northward since reintroduction began in 1970s (see Am. Ornithol. Union 1983, where range given as south from central and s. U.S.). Inland records for mid-Dec or Jan (Christmas Bird Counts; presumed wintering) from s. British Columbia (at least 49°N); in Alberta (generally south of 52°N) at such locations as Calgary, Cochrane, Bruce, and Monarch (Semenchuk 1992); environs of Winnipeg, Manitoba (B. Jones, W. Neily pers. comm.); rarely extreme s. Saskatchewan (since 1942, seen 1980, 1981, 1988; M. Williams pers. comm.); s. Ontario; Montreal (D. Bird, U. Banasch pers. comm.) and Gaspé Peninsula, Quebec; s. New Brunswick, and Nova Scotia (Halifax); occasionally in s. Greenland (older specimen records; Salomonsen 1950). In most major cities from Washington State, Minnesota, Wisconsin (Septon 2000), coastal Maine south through U.S. Neotropical. Spotty, with concentrations on coasts, in cities, and in wetlands (perhaps function of observer distribution; e.g., Risebrough et al. 1990). Throughout Caribbean (West Indies) south through Mexico, Central America to at least Chiloe I., Chile (42°30’S); high numbers coastally in at least Ecuador to n. Chile; n. South America and Netherlands Antilles (rare; Voous 1983) south throughout most of Brazil (except perhaps Brazilian Shield of s.-central Brazil). Of 117 locations in 18 Brazilian states where recorded, most in agricultural and urban habitats of ne. and s. Brazil (perhaps a function of observer concentration; Albuquerque 1978, Silva e Silva 1996), then south through Bolivia, Uruguay, Paraguay, and Argentina at least to Bahía Blanca at 38°S (W. G. Vasina pers. comm.) but probably to Gulfo San Matias at 42°S. West coast of South America to 40°S and about 4,100 m in Andes (Fjeldså and Krabbe 1990). top OUTSIDE THE AMERICAS Breeding range Worldwide breeder, as far east in Southern Hemisphere as Fiji and south to cape of South Africa and Tasmania, but absent from most of Saharan Africa, parts of central and e. Asian steppes, New Zealand, Iceland, and central Pacific Ocean, and Antarctica. In Palearctic, northern populations mainly migratory moving south to cape region of South Africa, Indian subcontinent, and Indonesia. Most southern populations and island endemics resident (Cade 1982, White and Boyce 1988, White et al. 1994). Winter range Most of breeding range except n. Scandinavia and tundra of Asia. Found in United Kingdom, most of Europe south of about 58°N, Asia south of 50°N, throughout Africa, Indonesia, Philippines, New Guinea and Australia, and eastward to Vanuatu, New Caledonia, and Fiji (Cramp and Simmons 1980, Stepanyan 1990, White et al. 1994). top HISTORICAL CHANGES Historically bred continentwide, from tundra south to nearly southern edge of Mexican Plateau, with good records from 1800s and beginning of 1900s; possible changes on mainland Mexico, but not recorded. Formerly bred in trees from Louisiana (1 nest known; Lowery 1974) north through parts of Mississippi River drainage (Tennessee, Indiana, Illin-ois) and west to Kansas (Goss 1898), and on gravelly/sandy river banks in midcontinent (Hickey 1969), but this distribution never well documented. Clearing of forests in East in 1800s may have broadened distribution, but tree removal along Mississippi River drainage eliminated tree nesters; last nest in Tennessee probably in late 1940s (Spofford 1947a). By early to mid-1900s, sites easily disturbed by humans were gone (north to at least 55°N), but this not well documented; generally most breeding then restricted to areas of larger cliffs throughout this range. Most complete documentation of former distribution in Hickey 1942, Bond 1946, and Cade 1960, until advent of major decline in numbers and loss of range after about 1950 (Hickey 1969). Well established that this range reduction and population decline resulted primarily from persistent synthetic chlorinated hydrocarbons (see Conservation and management, below). Many events in decline, and eventual recovery of species (mainly anatum), well documented or reconstructed (Hickey 1969, Cade et al. 1988, Enderson et al. 1995a). Changes in distribution too extensive to list in detail. Maximum extent of reduction in distribution may have occurred by 1972–1975 (variable in different places). In U.S., gone from the following locations: east of Rocky Mtns., Nevada, probably Montana, Wyoming, Canadian Maritime Provinces, most of Labrador, Quebec south of about 56°N, Ontario, Manitoba, Saskatchewan, most of Alberta, and n. Yukon Territory (Cade and Fyfe 1970, Fyfe et al. 1976). Elsewhere distribution and numbers reduced by varying degrees; e.g., California from >100 to 5 pairs, w. Texas and adjacent Mexico from 14 known to 11. Persistence in Mexican highlands through DDT era likely due largely to nonmigratory prey base (e.g., Band- tailed Pigeon [Columba fasciata], other nonmigrants) and lack of mechanized agriculture. Possibly little reduced in Arizona and adjacent Colorado Plateau of s. Utah, but historical distribution in Utah well known only in northern third of state (Porter and White 1973). Knowledge of distributional changes in Mexico marginal and best known in Baja California and Gulf of California; probably disappeared from Pacific coast of Baja (Banks 1969). Recovery and reoccupancy of historical range well on way by 1980 (Murphy 1990, White et al. 1990), in part because of release of captive-bred falcons by several organizations and breeders in Canada and U.S. (see Enderson et al. 1995a and Conservation and management, below, for details). Known distributional range expanded through 1980s–1990s across tundra and taiga of Alaska, and density even doubled over historically known numbers of 1950s in well-documented places like Colville (32 pairs in 1952 to 57 in 1997) and Yukon (about 20 in 1950 to 47 in 1997) Rivers, AK. In n. Alaska, distributional change has resulted from greater occupancy of tributaries of Colville and smaller rivers to east and on coastal plain (e.g., Barter I.; see Swem and Ambrose 1994; R. J. Ritchie, T. Swem, R. Ambrose pers. comm.; TJC; CMW). By 1996, even though somewhat clumped and spottily distributed, most of historical range reoccupied, although some pairs are urban (e.g., Iowa, Indiana, Illinois, Ohio) and not in original habitat. Distribution in parts of Midwest (e.g., Wisconsin) still largely urban or on human-made structures (Septon et al. 1996). Southern part of Mississippi River drainage (e.g., Tennessee, Louisiana) and most of n. Great Plains not reoccupied by 2000. top FOSSIL HISTORY No Peregrine Falcon fossils predate Pleistocene (about 1.6 million to 12,000 ybp). Most fossils are mid- to late Pleistocene and widespread at scores of locations in Pleistocene and Holocene prehistoric sites: e.g., Australia, New Caledonia, throughout Europe, Mediterranean region, Caucasus Region (Azerbaijan), North and South America (Brodkorb 1964, Malez 1988, Weesie 1988, Vickers-Rich et al. 1991). A recent origin is supported by cytochrome-b molecular data suggesting Peregrines separated from an ancestral stock around 2 mybp (Wink 1995). Within Americas, fossils from Ecuador (Campbell 1976), Peru (13,900 ybp; Campbell 1979) and several North American Pleistocene and Holocene prehistoric sites; e.g., Alaska, California (tar pits of Rancholabrean age 17,000–27,000 ybp), Arizona (11,940 ybp), New Mexico, Utah, Idaho, Ohio, Arkansas, Illinois, Penn-sylvania, Florida (Emslie 1988, S. D. Emslie pers. comm.). Several western fossil sites containing Peregrines date from about 40,000 to 29,700 ybp (Porter and White 1973). Some sites in California and Utah containing Peregrine fossils associated with human occupation (Howard 1929, Parmalee 1980); this falcon seemingly used by early humans as food. Those from Utah associated with human sites occupied by Archaic people (9,500–3,000 ybp; Parmalee 1980) around edge of Pleistocene Lake Bonneville that last existed about 10,000–11,000 ybp. Peregrine bones far outnumber Prairie Falcon remains at those midden sites, and Lake Bonneville ecosystem should have been prime habitat for Peregrines based on reconstructed envi-ronment and distribution and density of contemporary and historical peregrine eyries relative to extinct shoreline of Lake Bonneville.

SYSTEMATICS GEOGRAPHIC VARIATION | SUBSPECIES | RELATED SPECIES

GEOGRAPHIC VARIATION

Range of plumage variation in juvenile N. American Peregrines, as illustrated by J. Schmitt. See Systematics for details on each of the 3 subspecies.

Three subspecies of N. American Peregrine Falcons (adults), as illustrated by John Schmitt. Included here is one example of the Aleutian variant of the northwestern Peregrine (F. p. pealei). See Systematics for details. Exhibits variation in plumage coloration and morphometrics (see Appearance, below; Appendix 2); somewhat clinal on continent with Aleutian Is. Peregrines most distinctive and morphometrically uniform. Resident populations generally conform to Gloger’s rule (darker in areas of higher relative humidity) and Bergmann’s rule (larger size at higher latitudes); migratory northern breeders smaller, however (CMW in Porter et al. 1987). Birds breeding in cold, dry climates (F. p. tundrius) are palest; in hot, dry climates (F. p. anatum) have tints of browns and reds; in humid climates (F. p. pealei and some F. p. anatum) usually saturated with tints of darker grays and grizzle. ( View Video) During nonbreeding season, those resident farthest north (F. p. pealei) are largest, and smallest birds resident (F. p. anatum) in southern portions of breeding range or migratory (F. p. tundrius and F. p. anatum). Great individual variation can occur locally (e.g., n. Hudson Bay; Court et al. 1988), Gulf of Alaska (R. J. Ritchie pers. comm., CMW). Interpretation of this variation, while perhaps only a result of intergradation, is confounded by variation introduced by expanding gene pools of an earlier reduced population and biased contribution of particular genotypes; in 1990 on Tanana River, AK, young banded from a banded female were members of 6 pairs in a recovering population with 15 pairs (White et al. 1995). In recovering populations some variation will be short term until stabilizing selection occurs. Morphologically recognizable local populations still occur, or did (e.g., Four Corners Area, U.S., Okanagan Valley, British Columbia), suggesting genetically differentiated local populations and high philopatry. Each named subspecies has ≥2 subgroups, in some cases quite distinctive; e.g., Aleu-tian subgroup of F. p. pealei heavily marked on crop and throat of adult male and immature uniformly dark in pigmentation, while in Queen Charlotte Is. subgroup, crop of adult male is usually white and little marked and immatures from pale (tundra-like) to dark similar to those of Aleutians; F. p. tundrius from Greenland has longer wing and a statistically significantly wider malar-stripe than F. p. tundrius from remainder of range. Eastern F. p. anatum larger and darker than western F. p. anatum. In e. U.S., re-introduction of exotic subspecies and progeny from a small gene pool have produced patterns different from those of extirpated populations. It is not clear how rapidly morphometric characteristics can or will become fixed; also close inbreeding not infrequent (Tordoff and Redig 1999a). DNA microsatellite analysis of population genetic structure showed that samples of 3 North American subspecies were no more genetically distinct from each other than populations of nominate F. p. peregrinus from n. and s. Sweden (Nesje et al. 2000).

SUBSPECIES Nineteen subspecies recognized here, following White et al. (1994); 3 within North America: F. p. anatum, F. p. pealei, and F. p. tundrius (see C. M. White in Palmer 1988 for descriptions and distribution; see Appendix 2). So-called Pallid Falcon (F. kreyenborgi) of South America, apparently a color morph of subspecies F. p. cassini (Ellis and Peres 1983, McNutt 1984). Barbary Falcon, subspecies F. p. pelegrinoides (including F. p. babylonicus) found across n. Africa to central Asia (Mongolia), sometimes treated as separate species. F. p. anatum Bonaparte, 1838. North America south of tundra to n. Mexico, except Pacific Northwest. See discussion under F. p. tundrius. F. p. tundrius White, 1968. Arctic tundra of North America and Greenland. Museum specimens of predecline birds clearly demonstrate that a larger percentage occurred on pale end of variation, most noticeable in immatures, than following recovery, where now there is more overlap with pale variants of F. p. anatum, which also seem to have increased with recovery. May simply be stochastic as function of gene pool makeup prior to or during recovery. Immature, compared to F. p. anatum, more muted overall, upperparts more brown or umber than fuscous, with margins ochre to pinkish buff. Head much paler, often giving impression of totally whitish buff with pale-umber shaft lines; pale buffy-white ocelli more extensive. Malar- stripe thinner, often with horizontal break about 5 mm below eye and pale auricular frequently twice width of dark malar-stripe (see Plate 17b in Cade 1960, for example, from Yukon River, AK). Underparts background more buff than tawny, streaked with umber, frequently only as shaft lines on thighs in palest birds. Tail-bars similar to color of feather edgings of upperparts. Soft parts vary from blue-gray to greenish to pale yellow (e.g., legs and feet in 1 brood of 4 varied from pale blue to greenish to yellow, each different). Adult F. p. tundrius upperparts not as contrasting as anatum, head and upper back more similar to lower back and rump; less slaty, paler blue. Pale nuchal-collar or ocelli may be well developed. White forehead-band often as much as 10 mm. White auricular more extensive, frequently less than 10 mm from eye, although Greenland birds with wider malar-stripe, less extensive white auricular. Underparts less patterned, especially in center of belly, and frequently background wash appears slightly yellowish. F. p. pealei Ridgway, 1873. Coastal Pacific Northwest from Washington north to w. Alaska, Aleutian and Commander Is., and possibly Kamchatka and Kuril Is. In immature, wide variation in southern portion of range (3 more or less distinct variants), but generally darker overall than F. p. anatum. Upperparts typically more slate (chaetura black, with nuchal-collar) ocelli poorly defined, usually lacking edgings; where edgings occur, more whitish with subtle olive-grayish to olive-yellowish tint. Underneath usually lacking definite tawny background wash (more olive) except in palest individuals (which resemble F. p. tundrius). Underparts typically very much darker because streaking much wider, with streak sometimes covering entire feather, except for pale whitish-buff margin. Central rectrices most frequently without bars; occasionally pale spots in place of bars. Tail-tip whitish with greenish-yellow tint. Only dark variants known in Aleutians. Soft parts at fledging in Aleutian F. p. pealei pale yellowish. Adult F. p. pealei hard to characterize because of difference between birds in south part of range and Aleutians (darker, more heavily spotted, and lacking tints of yellow or buff), but upperparts more slaty, fuscous-black with lower back and rump less blue, so less contrasting with mantle and head than in F. p. anatum or F. p. tundrius. Usu-ally no or only hint of forehead-band except those in southern part of range, where forehead-band may exceed 10 mm. Background of underparts more whitish with tint of yellowish or olive. Markings color of back, but bold, broad, with spots and teardrops extending into crop (crop usually without spots, whiter, especially in southern portion of range). Soft parts in Aleutian F. p. pealei, at least, pale lemon yellow in contrast to deeper yellow orangish in F. p. anatum and F. p. tundrius.

RELATED SPECIES Peregrine Falcon formerly placed in separate genus Rhynchodon, now merged with Falco. Prairie Falcon clusters in same clade with Peregrine Falcon based on some courtship behavior, vocalizations, karyotype (macrochromosome pairs 48 in both species, fewer than other large falcons), and molecular data (based mainly on cytochrome b; Wrege and Cade 1977, Schmutz and Oliphant 1987, Helbig et al. 1994). Prairie Falcon thought closer to Peregrine Falcon than to Gyrfalcon (Steenhof 1998). Taita Falcon (Falco fasciinucha) is probably allied with Peregrine Falcon in same subgenus based on courtship, vocalization, and behavior (contra Cade 1982). Genus Falco placed in subfamily Falconinae (Tribe Falconini) according to phylogenetic analysis based on molecular (cytochrome-b gene of mitochondrial DNA) and morphological (syringeal supporting elements) characters (Griffiths 1999).

MIGRATION NATURE OF MIGRATION IN THE SPECIES | TIMING AND ROUTES OF MIGRATION | MIGRATORY BEHAVIOR | CONTROL AND PHYSIOLOGY

NATURE OF MIGRATION IN THE SPECIES Widespread during migration; e.g., mountains at 3,800 m above sea level (far above breeding range), offshore Atlantic routes (Kerlinger et al. 1983), mid-Pacific islands (perhaps not from North America; Clapp and Woodward 1968, Woodward 1972). In schematic outline, continental populations migrate in more or less “leap-frog” fashion (Schmutz et al. 1991, McGrady et al. 2002), but not uniformly. Northernmost tundra breeders generally move farthest south to central Argentina and Chile, with breeders farther south traveling shorter distances, but arctic and boreal nesters overlap considerably in winter distribution; some mid- to southern populations are resident, others at high elevations in Rocky Mtns. move south into Mexico are resident (White 1968a, 1968b; Yates et al. in Cade et al. 1988; Enderson et al. 1991; Schmutz et al. 1991). Individuals on nonbreeding (wintering) grounds in coastal e. Mexico and Central America with satellite transmitters moved to breed in Canadian Arctic and w. Greenland (McGrady et al. 2002, T. Maechtle pers. comm.), these birds winter-ing farther north than migrants from Wyoming and Colorado wintering in Sinoloa, Mexico (Molina and Cade 1990). Pale-colored falcons, presumably from tundra populations (not based on specimens), migrate south to at least Chiloe I., Chile (42°30’S) where they are seen at least Nov through Feb (R. Schlatter via C. Sadler pers. comm.). Most breeding populations not above 75°N and thus some one-way migration 12,400–13,300 km or more; one banded in Northwest Territories, Canada recovered 14,500 km south in Chaco, Argentina, less than 4 mo latter (Kuyt 1967). Two records of tundrius from Iceland, 1 on 30 Jul 1961, 1 on 16 Oct 1985 (British Birds 1997) top TIMING AND ROUTES OF MIGRATION Despite broad-front migration and widespread nature of movements (Anderson et al. and Yates et al. in Cade et al. 1988), there are clearly defined routes where Peregrines concentrate: along leading lines or coastal areas of prime habitat (barrier islands), particularly on Eastern Seaboard (Chincoteague and Assateague Is., MD-VA), Gulf Coast (Padre I., TX), and e. Mexico (Veracruz; Thiollay 1980, Heintzelman 1986, Hunt et al. 1975, Hunt and Ward 1988, Ward et al. 1988, Chavez-Ramirez et al. 1994, HawkWatch International pers. comm.). Lesser concentrations along shores of Great Lakes, West Coast of U.S., w. Mexico, and eastern front of Rocky Mtns. In South America, large numbers on west coast from Ecuador to Chile (Schoonmaker et al. 1985; Risebrough et al. 1990; C. M. Anderson, C. Gonzales, O. Beingolea pers. comm.). Typical migration from w. Greenland is west across Davis Strait, south in Canada and along U.S. East Coast either through Florida Keys to Caribbean (West Indies) and Central and South America or west around Gulf of Mexico, through Texas and Mexico to Central and South America. Large numbers now seen at off-shore oil rigs in Gulf of Mexico, associated with transgulf flights of passerines and shorebirds (A. Wormington in Pendergrass 2000, R. W. Russell pers. comm.). At autumn banding sites, adults tend to arrive prior to first-year birds; ratios about 1:1.7 along Great Lakes, 1:5.7 and 1:3.9 on Atlantic and Gulf Coasts, respectively, perhaps reflecting age difference in staging behavior (Mueller et al. 2000). Timing elsewhere generally similar; e.g., central Alberta spring migrants between 20 Apr–31 May, mid-dates for adults about 8 May, immatures 15 May (Dekker 1984). Missouri, spring peak last week of Apr, with autumn migration starting late Aug (peak late Sep–early Oct; seldom after Oct; Robbins and Easterla 1992). Ohio (mainly along Lake Erie) in spring, most 20 Apr–15 May; autumn, most 25 Sep–20 Oct, some as late as mid-Nov (Peterjohn 2000). Cape May, NJ, common in autumn, with total of 1,503 in 1996; daily maxima 206 on 1 Oct 1996 (96 in 1 h); fewer in spring, with peak first week of May (Sibley 1997). Bermuda, mainly autumn, 13 Sep–late Nov; rare in spring, late Mar to mid-Apr (Amos 1991). Costa Rica, mainly on Caribbean coast, occasionally Pacific lowlands; spring, Mar–early May, autumn, mid- Sep through Oct (Stiles and Skutch 1989). Throughout West Indies, but uncommon to rare, Oct–Apr (Raffaele et al. 1998). Until recently, most data came from collected specimens and banding returns (see Cade et al. 1988). More recently, Peregrines tracked with radio transmitters by aircraft (W. W. Cochran, private compilation from Illinois Nat. Hist. Sur. Repts. no. 304, 305, 312, 313) or satellite (Henny et al. 1996, Seegar et al. 1996, Hendricks 1997, T. Maechtle pers. comm.). Selected literature data from such techniques: Adult female trapped in mid-Oct 1993 on Assateague I., MD, flew to Guatemala, Honduras, Nicaragua, Ecuador, and then Bolivia; crossed Andes Mtns. to headwaters of Amazon River, finally ending up 6 Nov at 3,950 m at a saline playa, Salar de Antofalla, in the altiplano of Argentina, staying at oasis in the salar. Northward-migrating female trapped 22 Apr 1994 on Padre I., TX; stayed on eastern front of Rocky Mtns. in U.S., crossed Yukon Territory, and arrived at breeding grounds on Yukon River, AK, 31 May; left there 31 Aug, following a similar southward but more easterly route, arriving on Yucatán Peninsula 22 Sep, leaving there 3 Oct for Panama; then left Panama 19 Oct, crossed Andes, and arrived in Argentina 21 Nov. Lastly, 1 immature northward migrating female trapped 22 Apr on Padre I., TX, moved directly north through central Midwest to King William I., Nunavut, arriving 26 May; left 12 Oct, taking different route south, along west coast of Hudson Bay, leaving area of Churchill, Manitoba, 8 Nov, then south through e. Midwest to Gulf Coast east of New Orleans and to Yucatán Peninsula, apparently moving across Gulf of Mexico, by 25 Nov (Henny et al. 1996). Extralimital returns: A first year female (perhaps tundrius) trapped 14 Oct 1991 on Padre I., TX (C. M. Anderson, T. L. Maechtle pers. comm.), recovered 8 Dec 1993 at Misono-cho, Wakayama Pref., Japan (caught alive but died). One banded, also with color band, as nestling (anatum) on Colorado River, Glen Canyon NRA, AZ (M. Britten pers. comm.), photographed several times 17 Jan 1993 to 7 Feb 1993 in central Japan area of Mishima-shi. Both returns thought to have been assisted by marine vessel from west coast of North America to Japan where marine traffic is heavy. top MIGRATORY BEHAVIOR Data from radio transmitters from 7 individuals (see compilation from W. W. Cochran as above, Cochran 1975; also see Timing and routes of migration, above). Typical 24-h period included 17 h on perch, 6 h in migratory flight (range 1–9), 1 h hunting. When not migrating because of weather, loafing increased to 23 h/d. Migration on about 6 of 7 d, generally mid- morning to late afternoons. On average, flights 192 km at 33 km/h, but one individual went from Chicago to Tennessee in 1 d—560 km at 64 km/h. Efficiency in hunting during migration not necessarily a function of falcon’s age. A first-year bird averaged 53 min/d hunting, while one adult spent 93 min/d hunting before prey capture over a 5-d period. Chavez-Ramirez et al. (1994) found spring migrants flew more hours on average (12.02 h/d) than fall migrants (8.75 h/d). Considered a low-altitude migrant (mostly <100 m above ground level up to 900 m; Kerlinger 1989), but soars more than generally recognized. Average ground speed for flapping flight about 49 km/h (Cochran and Applegate 1986). Adults may use different routes from immatures over part of the migration. Telemetry data show spring migrants remain on Padre I. for average of 8.4 d (range 3–28; Hunt and Ward 1988); autumn migrants also stage on Padre I. In coastal Peru, ratio of adults to immatures 2:1, with most immatures seen in early winter (but differences may also suggest greater immature overwintering mortality; Schoonmaker et al. 1985). No apparent difference in time of arrival of the sexes on breeding grounds in northern latitudes (Court et al. 1988, Kerlinger 1989), although male often appears to arrive at cliff sites first. top CONTROL AND PHYSIOLOGY Not documented or clearly understood. Complex because migration distances vary, in part with breeding latitude. However, somewhat regular appearance at observation sites (e.g., barrier islands of Atlantic Seaboard and Gulf of Mexico) suggest Peregrines are less affected by passing of cold-weather fronts, which are irregular, than some other species. Alternative explanations for migration: movements of main prey items; photoperiod (e.g., predictable appearance at some observations sites and regular movements of transequatorial migrants). Some remain at certain northern latitudes (e.g., n. Pacific) where prey is available, while other populations at same or similar latitudes (e.g., Greenland) leave as prey moves; so in this example, photoperiod not regulating migra-tions equally. Some interior populations more likely to move than coastal populations where climate is moderate and prey species remain. Some genetic control may be involved, but many birds of northern origin raised and released in midlatitudes (35–40°N; G. Septon pers. comm.) do not migrate, as do birds of similar wild genetic arctic stocks (e.g., 3 adult females in downtown Milwaukee, WI, that wintered consistently there, differing from wintering behavior of original populations that bred nearby in Wisconsin and Minnesota; see papers in Cade et al. 1988 for above data).

HABITAT BREEDING RANGE | SPRING AND FALL MIGRATION | WINTER RANGE

BREEDING RANGE Many terrestrial biomes in the Americas; none seems to be preferred (although perhaps greater densities in tundras and coastally). Subtropical and tropical habitats occupied sparsely or not at all; most commonly occupied habitats contain cliffs, for nesting, with open gulfs of air (rather than in confined areas; see Breeding: nest site, below) and generally open landscapes for foraging (examples in Enderson and Craig 1979, Ellis 1982, Willey 1986, Grebence and White 1989). May breed to 3,600 m in Rocky Mtns. (J. Enderson pers. comm., CMW). In some regions, dispersion dendritic along rivers or shorelines of coasts and lakes as nest sites usually associated with water. In addition to natural habitats, many artificial habitats now used (urban, human-built environments such as towers, buildings, etc.). See also Breeding: nest site and Food habits: microhabitat for foraging, below. top SPRING AND FALL MIGRATION Broad array of habitats, including urban. Partial to leading lines such as barrier islands, seacoasts, lake edges, or mountain ranges; also at sea. See Migration, above. top WINTER RANGE Extreme habitat variability because of enormous geographical range. Other than resident populations, which occupy breeding habitats, may occur in open-relief habitat devoid of cliffs, as in midwest U.S.; man-grove, coastal, or wetland areas, as in Sinaloa, Mexico (Enderson et al. 1991); major river valleys and lake shores; pasture lands; featureless terrain devoid of cover and containing waterbirds or pigeons and doves (e.g., Atacama Desert of coastal Peru); and especially urban areas (Risebrough et al. 1990, Bird et al. 1996). top

FOOD HABITS FEEDING | DIET | FOOD SELECTION AND STORAGE | NUTRITION AND ENERGETICS | METABOLISM AND TEMPERATURE REGULATION | DRINKING, PELLET-CASTING, AND DEFECATION

FEEDING Main foods taken As generalized summary (14 studies: 1 from 1893, remainder published 1933–1974 from Sherrod 1978), mostly birds, estimated at about 77–99% (frequency not biomass), passerines to small geese; occasionally mammals and rarely amphibians, fish, and insects. Most frequent mammals: bats (e.g., Tadarida, Eptesicus, Myotis, Pipistrellus, etc.), microtines (e.g., Microtus, Dicrostonyx, etc.), squirrels (Spermophilus), and rats (Rattus). In California, fish and mice pirated from Ospreys (Pandion haliaetus) and Red-tailed Hawks (Buteo jamaicensis; B. Walton pers. comm.). Depending on habitat, predominant foods differ: tundra, ptarmigan (Lagopus), shorebirds (e.g., Pluvialis, Gallinago, Phalaropus, Calidris), small passerines, such as longspurs (Calcarius) and Snow Buntings (Plectrophenax nivalis), and ducks; taiga, shorebirds (e.g., Gallinago, Tringa, Actitis), woodpeckers (Colaptes), passerines (jays, thrushes); coastal marine, podicipe-dids, alcids, procellarids, waterfowl; interior continental, columbids (e.g., Zenaida), swifts, passerines; urban, columbids (e.g., Columba), cuckoos, rails, passerines. Overall, in temperate continental latitudes Columbidae (pigeons, doves) may be most frequently taken and perhaps most important by biomass. Microhabitat for foraging Most prey captured in air, while Peregrine is in flight; also from surface of water or ground; may walk on ground is search of nestling birds and rodents (Harris and Clement 1975; Dekker 1980, 1995, 1999; Rosenfield et al. 1995). Mexican free-tailed bats (Tadarida brasiliensis) regularly hunted at dawn and dusk at mouths of roosting caves on Edwards Plateau, TX (Stager 1941, Skutch 1951, Lee and Kuo 2001). Food capture and consumption Best described as sequence of actions consisting of search, pursuit (attack), capture, killing, and eating. Search. Peregrine searches either from perched position (most commonly) or while flying, sometimes on foot on ground. Especially in breeding season, adult perches on some high vantage point on cliff, usually near eyrie, overlooking vast air space in which other birds fly (see Treleaven 1977, 1998 for many examples along Cornish coast). Position allows falcon to stoop down easily on low-flying prey or to ring up after high-flying ones. Initial height above prey prior to attack was positively correlated with success in capture in Africa (Jenkins 2000). Aerial search performed either by flapping flight or when soaring at height; some parents search up to 15–43 km from eyrie (White and Nelson 1991, Enderson and Craig 1997). On Cornish coast, hunts from perches more successful (60%) than hunts initiated in air (40%); latter occurred mainly in bad weather when soaring not possible (Treleaven 1980). In fall and winter, often hunts from lower perches: trees, utility poles, fence posts, banks, mounds, driftwood—depending on habitat (Dekker 1980, 1999). Migrating Peregrine hunted from perches or in low flight in early morning (0.5 h before to 3.0 h after sunrise) and again following migratory movement after about 15:00; exceptionally launched attack during migration-soaring (Cochran 1975). Sometimes follows and uses human or animal to flush prey: gunners, harriers (Circus sp.), dogs (Canis familiaris), some-times machines (motorboats, harvesting equipment, vehicles; Palmer 1988, TJC). Of 318 attacks on ducks, 55% initiated while prey was not in flight or just after taking off (Dekker 1987). Sometimes hunts on foot after insects, other invertebrates, small mammals, and especially nestling and fledgling birds and precocial downy young (Sherrod 1983, Rosenfield et al. 1995, Dekker 1999). Particularly noted in Greenland, where passerines provide bulk of food. Pursuit (Attack). Several modes recognizable: stoop, ringing up, direct pursuit, contour- hugging, shepherding, running or hopping, and flapping on ground (see also Behavior: locomotion, below). Stoop is well-known mode: dive from above quarry, varying from <100 to >1,000 m long and from 90° angle to horizontal to <20°, in which gravity and body mass produce velocities in range of 25 to 100 m s-1; used to overtake and catch fleeing prey usually flying but sometimes running on ground or swimming in water. In shallow stoop or initial stage of steep one, falcon sometimes flaps wings, but in long, steep dives, wings are folded against body (Franklin 1999); rate of fall can be slowed by slight adjustments of wings, legs, and head (Tucker et al. 1998). Occurs over land and water. Most often stooping falcon pulls out of dive some meters behind escaping prey and shoots forward at great speed to grab or strike prey, or repeatedly stoops to force it down into water or onto open ground where it can be grabbed. Sometimes stoops directly down on prey, striking it in head, wing, or back, killing it or breaking wing (Cade 1982, TJC, CMW, WGH). Ringing up: Attack used to pursue birds initially flying higher than falcon. Two variations: (1) falcon spots bird flying high above cover (e.g., dense forest) and takes off to intercept it, circling up until it is slightly above quarry; then executes series of shallow stoops until quarry becomes exhausted and easily caught in air, or quarry attempts to escape by diving earthward to cover, in which case falcon dives be-hind it and catches up to grab or strike. (2) falcon starts with direct pursuit of low-flying quarry, usually where there is little ground cover. Prey attempts to escape by rising up into air faster than falcon (the classic haut vol of French falconry, in which slower but more lightly wing-loaded quarry [heron, kite, gull, owl] gains altitude by ringing up in tight spirals, while heavily wing-loaded but faster-flying falcon mounts in wide rings around the quarry). Falcon also maneuvers to keep quarry flying upward and from diving for cover, until it becomes exhausted and can be grabbed (bound to) in air (Rudebeck 1951, Cade 1982). Direct pursuit: Often when stoop is unsuccessful and prey flees by flying straight away, falcon follows directly behind (tail-chasing) in powered, flapping flight in attempt to overtake and grab prey. Perched or flying, falcon may see prey get up and fly away unhurriedly; then launches accelerated flapping flight (high-intensity hunting; Treleaven 1980) to intercept prey. Alcids and other waterbirds caught during high-speed, low-level flights over water, surprising prey on surface or as it rises from water. Fish also caught as they broke surface of water (Cade 1982). Contour-hugging ( View Video): Special form of direct pursuit in which falcon flies low, using concealing features of terrain or water (banks, fencerows, dunes, ridges, waves) to remain hidden from quarry until very close; in such surprise attacks, birds sometimes fly up directly in front of falcon and are caught before they can accelerate, while others freeze on ground or refuse to fly from water and are grabbed before they fly. Per-egrine uses surprise attacks more frequently than commonly thought (White and Nelson 1991, Dekker 1999). Shepherding ( View Video): When hunting, Peregrine attacks flocking birds, many species (e.g., pigeons, shorebirds, starlings, waxwings, Snow Buntings, Lapland Long-spurs, grosbeaks) avoid capture by massing in tight formation-flights that zigzag about the sky (Tinbergen 1951, Buchanan 1996, Dekker 1998). Falcon appears hesitant to strike into mass of close-flying bodies; in-stead repeatedly harries the group by diving at its periphery; occasionally a panicked bird breaks formation and is then vulnerable. Attack on ground: Sometimes lands and runs/hops and flaps after invertebrates, rarely reptiles, small mammals, and especially newly fledged birds and downy young of precocial species (waterfowl, shorebirds, gamebirds; TJC, CMW). Also runs down fallen birds injured in stoop. Capture and Killing. Captures mainly by grabbing prey with feet (binding) but rarely kills small prey by forcing talons into body as accipiters do. Instead, falcon bites into neck, disarticulating cervical vertebrae and severing nerve cord; even with prey killed in stoop, falcon bites into neck before feeding begins. Prey frequently killed this way while falcon is flying. Young bird performs this action first time it has in-tact prey, dead or alive, in its feet. Stooping or chasing falcon often flies in under prey and rolls over or flips up to grab from below or side, but also grabs from back, holding onto wings or neck of large prey (Cade 1982). More spectacular strike or blow delivered in stoop is less common method of stunning or killing prey (Treleaven 1998, Dekker 1999). Confusion exists as to how falcon performs this action. Older and aboriginal ideas that falcon strikes with its breast or wing butts refuted. Strike is made with feet, but how? Long be-lieved that falcon strikes with loose fist, back talon protruding as gashing device (see Fuertes 1920, Cade 1982), but High-speed cinematography revealed that all 4 toes are widely splayed at moment of contact, then immediately formed into fist after blow (Goslow 1971, M. W. Nelson film record). Many strikes may simply be failed attempts to bind at high speed, but some are delivered with enough force to displace or roll quarry several meters through air or cause it to bounce off ground on impact. Speed at which falcon reaches prey probably determines whether capture is by binding or striking. To grab, falcon must be near speed of prey to prevent momentum from pulling prey loose from talons. Some trained falcons learn to strike prey in head or gash pectoral area sufficiently to disarticulate from shoulder. Although some prey killed outright by striking, large prey (> size of falcon) usually only stunned and rendered easier to grab in air or on ground. Eating. After biting into neck, falcon carries small prey to habitual plucking perch (tree snag, cliff side, driftwood, building) for consumption, or to cache site. Prey too heavy to carry in flight are partially con-sumed on ground; remains may later be carried to eyrie or plucking perch, or left in place for later re-turn. Sometimes eats small prey, especially bats, while flying (Skutch 1951); male hunting over Colorado River in Grand Canyon caught and ate 7 bats in 20¿min of continual flight (TJC). Much variation depending on size of prey. Small bodies <100 g usually totally consumed after wings, tail, and some body-feathers deplumed; prey >250 g are picked clean of flesh and viscera, but skeletal elements left more or less intact. Wings with primaries still articulated with pectoral elements and sternum, sometimes neck also on larger birds; synsacrum and legs often remain articulated but usually separated from anterior skeleton; tail feathers usually plucked (Hagan 1952, TJC, WGH). Begins eating by tearing off head; usually consumed if small, picked apart and eaten or discarded if large. Continues by pulling apart and eating skin and flesh of neck (also bones of small prey), working down to breast. Depluming of breast precedes tearing into pectoral muscles, which are usually totally consumed. Viscera may or may not be eaten; often gut is pulled out and discarded, but remaining organs, especially heart and liver, usually eaten. Legs of large prey may or may not be picked clean (TJC, CMW, WGH). Appears to use tomial teeth to break long bones of wings and legs of smaller prey before swallowing. Large prey too heavy to carry back to eyrie are well plucked wing and tail feathers removed, head removed, eviscerated, and sometimes posterior half of carcass detached from breast, before latter carried back to eyrie to feed young. Hunting Success. Varies with age of falcon, hunger level, time of day, season, species of prey, and behavior of prey (Dekker 1980, 1995, 1999; Treleaven 1980; Bird and Aubry 1982; Roalkvam 1985; White and Nelson 1991). During winter in w. Washington, Peregrines hunting Dunlins (Calidris alpina) stooped directly at compact flocks with success rate of 47% (Buchanan et al. 1986) in estuaries, but rate dropped to 12.5% on coastal beaches (Buchanan 1996). Highest rate may be 93% (102 hunts) and 100% (68 consecutive hunts) by resident male still-searching and then ringing after high-flying migrants (mostly Blue Jays [Cyanocitta cristata]) over New Jersey salt marsh (Cade 1982). For 23 different studies, average success rate was 23.7% (range 7–83%); outside breeding season, adults significantly more successful than immatures (12.7 vs. 7.3%; p < 0.01), and breeding-season adults were si-gnificantly more successful than adults outside breeding period (34.9 vs. 12.7%, p < 0.001; Roalkvam 1985). Motivation of falcon, indicated by high- and low-intensity hunting (Treleaven 1980), appears to influence success rate greatly and sometimes leads to false impression that Peregrine is inefficient hunter. top DIET

Peregrine Falcon with its prey (a pigeon); Jones Beach St. Pk., LI, NY; Feb. Main foods taken For North America, minimum of 429 species of birds, 10 bat species, and 13 other mammal species recorded (190 for California alone; B. Walton pers. comm.). Exceptionally, fish (4 species) and insects (mainly Orthoptera [grasshoppers, crickets] and Odonata [dragonflies, damselflies]) also. Rarely carrion (Holland 1989). Estimate of “well over 250 species” of birds captured worldwide often given (Palmer 1988: 378), but that number almost certainly exceeds 1,500 and probably 2,000 species. Primary literature on foods in North America too vast to be cited. Birds as large as Sandhill Crane (Grus canadensis; about 3,100 g) hit in the head and killed in midair in Alaska (CMW), also Bald Eagle (about 4,700 g) hit in head in Arizona, although probably not for food, and found dead within a month apparently from injuries exhibited during month (Hunt et al. 1992). Smallest items, hummingbirds (Selasphorus, Archilochus spp.; 2.5–3.5 g), largest items in eyries, small geese (Brant [Branta bernicla]; 1,400 g; Cade et al. 1968). But known to have killed a small Canada Goose (Branta canadensis leucopareia), 1,700–2,200 g, on the ground (Stabins 1995). Frequently captures extremely aerial birds such as White-throated Swift (Aeronautes saxatalis), especially on Colorado Plateau, and Black Swift (Cypseloides niger) on San Juan Is., WA (C. M. Anderson pers. comm.). Of 20 prey captures seen in bottom of Grand Canyon, 45% were White- throated Swifts, remainder bats (Brown 1991). Quantitative analysis Dietary composition varies greatly among regions, habitats, seasons, age, and even individuals. Diet mainly quantified from prey remains at nest and plucking perches, less often from observations at nests (e.g., Greenland; Harris and Clement 1975, Rosenfield et al. 1995) and least from pellets (difficult to determine prey items), and stomach analysis (Henderson 1927, Snyder and Wiley 1976). Each method has drawbacks, usually underestimating some category of prey. Following are typical prey lists, frequently not quantified. Informative because of the nature or diversity of species, reported for several habitats: (1) Across tundra, prey diversity decreases west to east, probably reflecting bird diversity. Alaska: 47 species minimum; most frequent prey may change annually (e.g., jaegers [Stercorarius spp.], 2% in 1 yr [n = 98], to 16% [n = 204] following year), but Common Snipe (Gallinago gallinago), golden-plovers (Pluvialis sp.), Gray-cheeked Thrush (Catharus minima), Yellow Wagtail (Motacilla flava), Lapland Longspur (Calcarius lapponicus), and American Tree Sparrow (Spizella arborea) consistently high. Nunavat: 28 minimum prey species with waterfowl, Rock Ptarmigan (Lagopus mutus), Horned Lark (Eremophila alpestris), American Pipit (Anthus rubescens), Lapland Longspur, and Snow Bunting most frequent; among all Nearctic Peregrine populations yet reported, may have as high as 29% (about 15% biomass) mammalian food, lemmings (Dicrostonyx and Lemmus), and ground squirrels (Spermophilus), making difference between marginal and good breeding success in some years (Court et al. 1988). Greenland: 11 species minimum, with 87% (frequency) made up of just 4 passerines: Lapland Longspur, Snow Bunting, Northern Wheatear (Oenanthe oenanthe), and redpoll (Carduelis spp.); also Rock Ptarmigan, 6% (Cade 1960, White and Cade 1971, Falk et al. 1986, Court et al. 1988, Bradley and Oliphant 1991, Rosenfield et al. 1995). (2) In taiga (Alaska), prey taken more diverse than in tundra; minimum 60 species recorded. Depending on year, most important species varied: Lesser Yellowlegs (Tringa flavipes), 1.5– 22.8% frequency (0.8 to 15.9% biomass); Gray Jay (Perisoreus canadensis), 5.1–19.2% (2.7–11.1%); Spotted Sandpiper (Actitis macularia), 3.0–10.2% (1.0–2.6%); Common Snipe, 3.8–8.8% (3.5–7.7%). Other frequently taken species: Catharus thrushes, Varied Thrush (Ixoreus naevius), Bohemian Waxwing (Bombycilla garrulus), and Northern Flicker (Colaptes auratus). By frequency in some years, passerines were 52% and ducks and grebes only 14%. By biomass, however, waterfowl and grebes made up to 63%, piciform and passeriform 22%, shorebirds 12%, and passerines as little as 11% in 1 study (Cade 1951; Cade et al. 1968; Hunter et al. 1988; A. G. Palmer, D. Nordmeyer, and D. D. Roby unpubl.). (3) Region of entire Pacific Coast shows some uniform characteristics in 4 sample regions, Aleutian Is., British Columbia, Channel Is., Baja California. At minimum, 78% (frequency) of food composed of alcids (auklets, murrelets) and procellariids (storm-petrels, shearwaters). In northern regions, alcids >75% of diet (Beebe 1960, White et al. 1973, Nelson and Myres 1976). Departure from marine-based prey in some eyries on islands in the Gulf of Georgia, British Columbia, where 85% of prey (frequency) is European Starling (Sturnus vulgaris; R. W. Campbell pers. comm.). In Aleutians, minimum of 31 bird species and 1 mammal species taken. In Baja California, 99 bird species and 2 mammal species taken; numerical importance in Gulf and Sea of Cortez are Eared Grebe (Podiceps nigricollis), Black Storm-Petrel (Oceanodroma melania), and Red Phalarope (Phalaropus fulicaria; equal), Craveri’s Murrelet (Synthliboramphus craveri) and Mourning Dove (Zenaida macroura; equal), Bona-parte’s Gull (Larus philadelphia), Northern Phalarope (Phalaropus lobatus), Least Storm-Petrel (Oceanodroma microsoma), and Heermann’s Gull (Larus heermanni), but order by biomass is Eared Grebe, Craveri’s Murrelet, Black Storm-Petrel, Bonaparte’s Gull, Red Phal-arope, and Mourning Dove. Within gulf, fishing bat (Myotis vivesi) was caught more frequently than any passerine and as or more frequently than anatids, ranking about equal to Heermann’s Gulls (Porter et al. 1988, R. D. Porter and M. A. Jenkins unpubl.). In California Channel Is., gulls and alcids make up 66% of prey biomass in winter, 38% in spring (WGH). (4) On neotropical nonbreeding grounds, many observations but no extensive published synthesis. Food varies regionally, somewhat by sex and habitat. Because many migrant falcons concentrate coastally, in urban centers, or in regions also occupied by other neotropical migrants, the latter, especially Charadriiformes, figure heavily in diet; e.g., North American waders (Risebrough et al. 1990). In n. Chile, 1 falcon occupying coastal city rarely took urban feral pigeons but went to sea for marine birds, especially phalaropes (Phalaropus spp). In one study along Chilean coast, with a few hundred prey remains of 35 species, most important were Nearctic Red Phalarope, at 18%; Franklin Gull (Larus pipixcan), 10%; Ruddy Turnstone (Arenaria interpres), 7%; and resident feral pigeons, 12%, and White-winged Dove (Zenaida asiatica), 6% (C. Gonzales unpubl.). Common Tern (Sterna hirundo) and Sanderling (Calidris alba) frequently mentioned prey in Peru (Bertochi et al. 1984, Blokpoel et al. 1989). In or near urban regions, especially e. South America, feral pigeons (80+%) and bats (Molossus spp. and Tadaris spp.) important (11+%; Pierson and Donahue 1983, Risebrough et al. 1990, Silva e Silva 1997, J. L. B. Albuquerque pers. comm.). In Panama during winter over several years on same skyscraper, 1 female ate only neotropical migrants, no resident species (B. Walton pers. comm.). Bats frequently killed over water and retrieved from surface. (5) Urban areas (breeding) refer to metropolitan centers, bridges connecting those centers, and associated power plants or near-urban areas (Bell et al., Cade et al., Septon et al., in Bird et al. 1996, J. B. Marks pers. comm.). Minimally, prey items exceed 117 species of birds, 6 mammals, and 1 fish: as expected, by percent, domestic or feral Rock Dove, Mourning Dove, Northern Flicker, European Starling, Blue Jay, and American Robin (Turdus migratorius) are major foods. Because power plants and bridges are near aquatic areas, grebes (Podiceps, Podilymbus spp.) and rails (Rallus, Porzana spp.), American Woodcock (Scolopax minor), and other shorebirds commonly taken. top FOOD SELECTION AND STORAGE Individual falcons and pairs often prey selectively on particular species and classes of prey. Selection appears related to factors that increase vulnerability of prey rather than to abundance per se, although latter can be factor influencing vulnerability too. Factors related to vulnerability and selection can be species-specific as well as specific to characteristics of individual prey. They include mass, plumage patterns, flight characteristics, oddity of appearance or behavior, molt or accidental loss of feathers, sickness or injury, and occurrence in unfamiliar or atypical habitats. Average mass of prey difficult to determine as it varies regionally and may vary annually and season-ally; approximate mode of prey mass in Alaskan taiga 81 g, in Aleutians and Pacific Northwest about 185 g, in many urban sites about 189 g in summer and 350 g in winter. Prey caught mostly in range of 50–500 g, perhaps optimal size in relation to aerodynamic characteristics and striking/grasping capabilities of falcon. May be selective tradeoff between advantage for aerial pursuer to be near to, or smaller than, size of escaping prey and capability of holding and killing large prey; latter may explain large size of feet and use of stoop to stun or kill large prey (see Cade 1982). Often selects birds with conspicuous flash patterns in flight (e.g., flickers, Blue Jay, Clark’s Nutcracker [Nucifraga columbiana], Red-winged Blackbird [Agelaius phoeniceus], meadowlarks [Sturnella spp.], shrikes [Lanius spp.; Craighead and Craighead 1956); also, male ducks taken more frequently than females in breeding season (Cade 1960). Male birds with con-spicuous aerial courtship or territorial displays often taken during performance (e.g., Common Snipe, Lesser Yellowlegs, jaegers, Short-eared Owl [Asio flammeus], swifts [probably during aerial copulation when mates are locked together in falling flight; J. H. Enderson pers. comm., TJC], Yellow Wagtail, Horned Lark). In interior Alaska taiga, 2-yr study tallied 83 avian taxa taken by Peregrines: 12 (14%) in 1985 and 11 (13%) in 1986 taken more frequently than expected by relative abundance within 3 km of eyries. Most selected species in descending order: Lesser Yellowlegs, Gray Jay, Spotted Sandpiper, Common Snipe, Solitary Sandpiper (Tringa solitaria), Bohemian Waxwing; 42 (51%) and 47 (57%) of taxa preyed on in proportion to their availability; 29 (35%) and 25 (30%) taken less frequently than expected from availability (Hunter et al. 1988). In w. Greenland, Lapland Longspurs, most abun-dant prey species, were most often delivered to nest, but Rock Ptarmigan and Snow Buntings were taken more frequently than expected from their relative abundance on prey transects; Northern Wheatears and Common Redpolls (Carduelis flammea) taken less frequently than expected; most prey were fledglings (Rosenfield et al. 1995). Also, passerine abundance increased with increasing distance from Peregrine eyries (Meese and Fuller 1989). In North America, other species apparently taken out of proportion (more frequently) to relative abundance include: rails and coots; small to medium-sized ducks (Dekker 1999); auklets and murrelets among seabirds (Beebe 1960, Nelson 1977); golden-plover, Dunlin, Pectoral Sandpiper (Calidris melanotos), American Avocet (Recurvirostra americana), Black- necked Stilt (Himantopus mexicanus), Willet (Catoptrophorus semipalmatus), oystercatchers (Haematopus sp.), and Black Skimmer (Rhynchops niger) among shorebirds; small gulls among Laridae; cuckoos; thrushes and jays among passerines (TJC, CMW); and especially doves and pigeons. Unusual items are Budgerigar (Melopsittacus undulatus), Monk Parakeet (Myiopsitta monachus), Cockatiel (Nymphicus hollandicus), and an array of other escaped caged parrots that are quickly selected because they are oddly conspicuous or naive. Wherever they occur throughout range of Pere-grine, pigeons and doves—in particular Columba livia, wild, feral, and domestic—usually make up bulk of this falcon’s diet (Ratcliffe 1993); Mourning Dove frequently taken in North America, as are White-winged Dove and Band-tailed Pigeon locally. These fast-flying, maneuverable birds with loose body-feathers are well adapted to elude capture; yet for reasons not understood—perhaps having to do with taste, nutrition, or regularity with which they must travel to and from water sources, particularly during breeding—falcons pursue them relentlessly and catch many. Migrating Peregrines often prey on other small migrating raptors: American Kestrels (Falco sparverius), Merlin (F. columbarius), especially Sharp-shinned Hawk (Accipiter striatus; Dry Tortugas Is.; T. Smylie and J. Weaver pers. comm.). Frequently hunts by sitting and watching activities of birds within its field of vision about 2-km radius allowing many birds to pass unchallenged, apparently waiting for disadvantaged individual or an especially stimulating one. Examples: odd black or white pigeon in a flock, homing pigeons released over unfamiliar landscape in Scotland (Ratcliffe 1993); stray Black Brant far inland along Yukon River (Cade 1955); land bird crossing an expanse of water (e.g., Gray Jay crossing the Yukon, Cade 1960); sometimes exhausted migrant songbird or sandpiper far from escape cover (e.g., Blue Jays and American Woodcock along Atlantic coast, Cade 1982); seabird flying over land (e.g., Dovekie [Alle alle], in Greenland, auklets on St. Lawrence I., AK, Marbled Murrelet [Brachyramphus marmoratus], in California; B. Walton pers. comm.). Some individuals and pairs fixate on 1–2 prey species to virtual exclusion of everything else: migrant Sharp-shinned Hawks, nestling boobies (Sula sp.), doves and pigeons, avocets and stilts, murrelets and auklets, terns (Sterna sp.), corvids, and arctic passer-ines. Selective predation by Peregrine may well have both sanitary effect by culling weak, injured, unfit individuals from prey populations, as well as evo-lutionary influence on form and function of some species, particularly columbiforms. Fixation by falcons on 1 prey kind or class probably leads to increased skill in capture. Peregrines cache and store surplus prey, especially during breeding season. Cache sites vary greatly: often in crevice or hole on cliff face near eyrie; under dense bush or in clump of grass on ledge or top of cliff; at base of fence post or dead tree; under drift wood or log, in marshes; sometimes in cavity or crotch of tree; on building ledges, recessed features, drain holes, under bridges, behind billboards and signs in urban areas. Male sometimes begins to cache early in breeding season before female arrives (unmated male on building in Boise, ID, accumulated cache of >20 Mourning Doves laid out in row on window ledge next to nest box; TJC). Cached prey often used in courtship feeding; sometimes male entices female to take cached prey before bill-to-bill transfers begin (Nelson 1977). Prey often cached with head attached (Beebe 1960, TJC, CMW) but also headless; partially eaten carcasses also cached after feeding young. Nesting female observes where male caches and may take cached prey when male is slow to deliver food directly to her. Caching appears to also be response to both daily and multiple-day periods when prey is unavailable (e.g., prey available only at crepuscular times or nocturnal, such as Ancient Murrelets [Synthliboramphus antiquus] on Langara I.), and when general unavailability of prey during stormy conditions (Nelson 1977, Fox 1979, Cade 1982, Ratcliffe 1993). At site in downtown Milwaukee, food including cuckoos (Coccyzus spp.) was cleaned from cache several hours after civil sunset; then cache again contained cuckoos 2–3 h before civil dawn, indicating nocturnal hunting, perhaps aided by city lights (Wendt et al. 1991). top NUTRITION AND ENERGETICS

Relatively few data, mostly from captive birds. Energy determined by body mass (Mb; larger female uses less mass-specific energy than male; thus total energy use is roughly equivalent between sexes), by ambient temperature, and by physiological work performed; total food consumption further influenced by nutritional quality of diet and efficiency of assimilation. In fall–winter conditions (average Ta = about 0°C), 3 males with mean Mb of 683 g (607–727 g) main-tained Mb by consuming mean of 104 g/d (101–107 g) of mainly lean beef with supplements (15.1% Mb/d); one 721-g male in spring–summer (average Ta = about 20°C) maintained Mb by consuming 83 g/d of same diet (11.5% Mb/d; Craighead and Craighead 1956). Amount of food for maintenance in laboratory con-ditions measured 89.2 g/kg Mb/d (Duke 1986), but sex and type of food not specified. In experiments on digestive efficiency (Barton and Houston 1993), 3 males with mean mass of 550 g (510–565 g) at 0°C consumed average of 142.3 g/d (141–143 g) of 1-d-old cockerels minus yolk sac and intestines (25.8% Mb/d) with digestive efficiency of about 75.3%; at 20°C, 5 males with mean mass 570 g (535–600 g) maintained Mb by consuming average of 94.5 g (78–117 g) cockerel/d (16.6% Mb/d) with digestive efficiency of 76.3%; 4 females with mean mass 789 g (740–896 g) consumed mean of 113.7 g/d (91–134 g) same diet (14.4% Mb/d) with efficiency of 74.0%. Circulating levels of vitamins and minerals in-fluenced by diet. In captive birds, levels lower than in wild and poor nutrition affects appearance of soft parts (cere, feet), hatchability of eggs, and vigor of hatchlings. No age or sex difference noted in vitamin A/E or mineral levels of wild birds (Dierenfeld et al. 1989, NJC). Captive females subject to multiple-clutch-ing exhibited depressed levels of vitamins A/E relative to captive males (NJC). top METABOLISM AND TEMPERATURE REGULATION

Oxygen consumption or CO2 production not mea-sured; metabolic rate higher than other congeners in North America based on frequency and amount of food consumption, especially in relation to Ta (D. Bird pers. comm.). Thermoregulation accomplished primarily by behavioral mechanisms that modify radiative and convective heat transfer, by adjusting body insulation to decrease conductive heat loss, and by evaporative cooling. Behaviors include seeking favor-able microclimates, changing orientation of body relative to sun, changing position of extremities (e.g., drooping legs or wings, tucking in feet), erecting or depressing feathers to change levels of insulation, and panting. In American Kestrel (Falco sparverius), and presumably Peregrine, primary route of radiative/convective heat transfer is bare tarsus (Bartholomew and Cade 1957, Mosher and White 1978). As expected, tarsal index (tarsal surface area divided by body weight) of falcons is related to climate, with species from cooler climates having less tarsal surface area. Males also tend to have higher tarsal surfaces than females. Most Peregrines able to maintain relatively constant cloacal temperatures over a span of 20–50°C. Indications that tundra Peregrines (F. p. tundrius) may be able to maintain more constant Tb over wider range of Ta than Peregrines at lower latitudes (F. p. pealei) or other species (Mosher and White 1978). top DRINKING, PELLET-CASTING, AND DEFECATION Drinks frequently, often when bathing. Pellets usually egested once/d early in morning prior to feeding. They are long and oval; about 16 × 41 mm (1.44 g dry) for female and 13 × 29 (0.80 g dry) for male; consist mainly of feathers (or fur), with some bone (usually broken), and hard indigestible parts such as gizzard linings, bills, and toenails. Sand, gravel, and small, usually rounded, stones (gastroliths “rangle”), usually between 6 and 12 mm and as large as 20 × 20 mm, eaten; may be used to clean stomach, promote gastric stimulation, or slough koilin lining; also associated with falcons that have fasted before eating the rangle (Albuquerque 1982, Cade 1982). May do so up to once a week. Nestlings eject fecal material away from nesting scrape, often causing buildup of fecal material on back walls of nesting ledges or at front edges of ledges. top

SOUNDS VOCALIZATIONS | NONVOCAL SOUNDS

No sound in nature is more compelling and exciting to the ear of a falcon searcher than the clear, raucous cacking of an angry Peregrine defending her eyrie or the shrill begging calls of her young beckoning across a distant landscape. top VOCALIZATIONS Development Predominant vocalization of young is the Beg, beginning just prior to or just after hatching. A repeated, broad-band (1–9 kHz), relatively long call (0.5–0.8 s), with moderate intercall interval (0.2–0.3 s) and very distinct harmonic structure; a repetitive, screea, screea, screea that becomes slightly lower in frequency with age. Early in development (first week), structure of call strongly resembles that of adult Wail (see below), but gradually becomes noisier and harsher, resembling adult cack (see below). Calls of individuals have a high index of similarity within calling bouts (>90%), but calls from same individual at different ages are initially less similar to each other than those of different individuals at same age (NJC); probably a function of physical changes in syrinx due to growth. Call structure begins to stabilize about 7 d for male and 9 d for female (NJC). Sex differences of adults (see below) also present in young (NJC). Young utter Beg during feeding or in presence of adults, especially upon latter’s arrival at eyrie. Muffled, closed-mouth version given while visually searching for absent parents. When food is offered by adult, call resembles Whine (see below); taking of food often accompanied by a singular resonant yack from donor, recipient, or both (Herbert and Herbert 1965, Weaver and Cade 1978, Hustler 1983, Marchant and Higgins 1993). In wild, young will hiss when approached by humans and other animals at 2–3 wk old; in captivity, presence/timing of this response dependent on rearing. By 3–4 wk young have acquired cack vocalization (Ingram and Salmon 1930), and use a very loud, demanding version of adult Wail to solicit food (Cade 1960, Hustler 1983), the sound carrying to human ear over distances of 1.5–2.0 km. Older nestlings and immatures grunt; a singular, deep, ugh when surprised at close quarters (references in Cramp and Simmons 1980, NJC). No evidence of vocal learning. Birds raised in isolation exhibit full repertoire of calls. Vocal array Most vocalizations associated with aspects of reproductive behavior. Usually quiet away from eyrie, except for intra- and interspecific aggressive encounters. Repertoire of male and female similar, also to other falcon species, but relative frequency and context of vocalizations vary with gender and species. No geographic differences noted among wild birds of 4 subspecies observed in captivity (F. p. tundrius, F. p. pealei, F. p. anatum, F. p. brookei; Wrege and Cade 1977). Quantitative sex differences occur in sound frequency and in power spectra; male calls approximately 0.2 kHz higher than female, and male calls often encompass a broader range of frequencies and have more distinct harmonic structure (see sonograms in Cramp and Simmons 1980). Male and female cack vocalizations can be distinguished with about 90% accuracy (Telford 1996). Individual recognition of cack vocalizations is possible with 72–90% accuracy on average, and recognition of calls is highly repeatable across years and observers. Frequency characteristics appear most useful for distinguishing calls, as opposed to temporal characteristics or patterns of frequency modulation within calls (Telford 1996). Historical emphasis on phonetic descriptions of calls has created some confusion regarding categorization of calls, but most Peregrine vocalizations can be placed in 1 of 4 categories based on structure: cack, Chitter, eechip, and Wail. With exception of cack, each vocalization is used in multiple contexts. Variation in intensity reflected in changes in call structure and may signal both quantitative and qualitative changes in motivation (Wrege and Cade 1977). See Cramp and Simmons 1980 for variations on phonetic descriptions of calls. Chitter ( View Video). Repeated, relatively short (0.15 s), broad-band (1–9 kHz), harmonic call with moderate intercall interval (0.1–0.2 s); a harsh kak kak kak kak kak, often repeated incessantly. Call of female tends to be more rapid, with a shorter intercall interval than male (see sonograms in Cramp and Simmons 1980). Given in alarm and in conjunction with nest defense. May increase in speed and pitch with increasing intensity (Herbert and Herbert 1965), but speed of calling decreases when actually attacking; upon contact, call degrades into a shrill, fragmented, kaa-aa-ack, kaa-aa-ack (Cade 1960, Herbert and Herbert 1965). Chitter. Repeated, very short (0.02 s), broad-band (0–5 kHz), harmonic call with very short (0–0.02 s) intercall interval; a feverish chi chi chi chi chi occurring in bursts of 5–12 repetitions or continual up to several seconds). In wild and captivity, most frequently given by male prior to or during copulation (in association with Hitched-Wing Display) and during copulation (Nelson 1977, Wrege and Cade 1977, Hustler 1983); occasionally given by either sex in alarm (Nelson 1977, Marchant and Higgins 1993). In captivity, may be given by either sex during agonistic Head-Low Bow Display, when forcing mate off eggs, or by female when forcing Food Transfer. In cases of extreme alarm, degrades into Scream (TJC, NJC). Eechip. Repeated, 3-part call of variable but relatively long duration (0.25–0.8 s) and intercall interval (0.1–0.8 s). In its most complete form, a sharp, deliberate, ku ee chip, ku ee chip from which either the ku or ee or both may be dropped. The ku, which contains the least energy of the 3 elements, covers a lower range of frequencies (0–4 kHz), has an indistinct harmonic structure, and is about 0.05 s in duration. The ee, which follows within 0.01 s (when present), is a rising, single-band, frequency- and- amplitude-modulated sound that begins at about 4.5 kHz, plateaus about 5 kHz, and is about 0.08 s in duration. The chip (or chup of female) contains most energy, covers broadest range of frequencies (1–6 kHz), has distinct harmonic structure, and has longest duration (0.1 s; NJC). Used by both sexes in wild and captive birds in association with various forms of Head-Low Bow Display, within the context of Individual and Mutual Ledge displays, and during Food Transfers. In captive birds, also given by male during or immediately following copulation. In wild birds, given during aerial encounters with conspecific intruders around nest site; exact motivation unclear (Cade 1960, Nelson 1977, Telford 1996). With increasing proximity to mate, call increases in speed and intensity and ku and ee syllables tend to be dropped. As intensity decreases, call may degrade to Peeping, in which only dominant frequency of the chip remains (2.0–4.0 kHz), slightly attenuated to almost continual; may be interspersed with ku or chip elements. Peeping generally associated with Billing and/or termination of Ledge Display (Wrege and Cade 1977). Wail. Continual or repeated, relatively long call (0.4–2.0 s), with irregular intercall interval (0.1 s to several min). Less noisy with more distinct harmonic structure than other calls and more even distribution of energy across frequencies (1–6 kHz), rising slightly in frequency over time; a querulous waiiiik. Has widest variety of forms/contexts of all calls; forms include Wail, Whine, and Beg (see above). The Wail appears in several contexts: Food Wail, Agonistic Wail, Copulatory Wail, and Advertisement Wail. In captive and wild birds, most common is Food Wail, given by either sex prior to Food Transfer. In this context, calls tend to be shorter (0.5 s), more frequent, and more regularly spaced, with energy concentrated at 2–3 frequencies. Less common is Agonistic Wail; in captivity, given by either sex in association with territorial behavior or by female when signaling male to move. In wild, associated with self-defense or defense of food (mantling; Nelson 1977, Hustler 1983). In this context, call tends to be slightly longer (0.7 s), with energy distributed across 3–4 frequencies; may precede a cack or Scream. Copulatory Wail is given by captive female during coition (Wrege and Cade 1977); not documented in wild birds. This form is longer (1.0 s), with energy distributed across 3–4 frequencies, repeated 2– 4 times (i.e., until copulation attempt terminated). Adver-tisement Wail is given primarily by male, spontaneously, apparently randomly, and usually in absence of mate (Carlier 1995) or intruders (Nelson 1977); frequently heard after nest failure (TJC). No quantitative information, but qualitatively less intense than other forms. Whine is most structurally and contextually distinct of this group of calls. Typically consists of single band about 4 kHz, extremely attenuated (2–3 s), rising slightly in frequency and amplitude. In wild and captive birds, given by female during solicitation; a more abbreviated version occa-sionally given prior to Food Transfer. Beg (see description above) sometimes given by wild adult female immediately before Food Transfer from male. Phenology Most calls limited to the reproductive period, except cack and Agonistic Wail, either of which may be given in response to individual alarm. Even cack, to extent that it functions in territorial defense rather than self-defense, is probably more common during breeding. Phenology of vocalizations follows seasonal ontogeny of reproductive behaviors. Chronologically, Wail may occur first, given its function in advertisement, followed by cack and eechip, in association with territorial defense and courtship. Frequency of nest defense, and therefore territorial vocalizations, highest during courtship and decreases significantly as reproduction progresses (Court 1986). Frequency of eechip in reproductive displays, however, increases steadily throughout breeding, as does Wail (Carlier 1995), in association with Food Transfers. Chitter, Whine, and Copulatory Wail are most preva-lent the month preceding egg- laying, in association with solicitation and copulation (Wrege and Cade 1977). Daily pattern Not specifically documented. Territorial vocalizations (cack, eechip) occur in response to intruders and activities of other animals at any time. In captive birds, vocalizations associated with reproductive displays most common in 4 h following sunrise and preceding sunset (Wrege and Cade 1977). Birds breeding at higher latitudes show less distinct temporal patterns. Places of vocalizing Site of vocalizations determined by site of behavior, usually within immediate vicinity of nest site. In captive and wild birds, cack given from nest ledge or perch or in flight. In captive birds, Chitter, Whine, and Copulatory Wail typically occur at nest ledge, but in wild birds may occur as frequently on perch. In wild birds, Chitter also given in flight in a defensive context. Eechip may occur at nest ledge, perch, or cache (reproductive context), or in aerial chase. All vocalizations of young birds occur at nest ledge until about 5 wk old, when they begin to move about cliff. Female Beg may be given in air or from perch. Food/Agonistic Wails may be given at nest ledge, from perch, or in air. Advertisement Wails given from perch or in flight (NJC). Repertoire and delivery of calls With exception of sexual differences, all individuals appear to exhibit same repertoire of calls, although there is individual variation in structure, context, and frequency. First-year breeders appear to have same repertoire as older breeders, though phenology is accelerated (Wrege and Cade 1977). Little information on vocal repertoire of adult nonbreeding birds, but with exception of cack and Wail, other vocalizations probably not used with any frequency until first year of reproduction. Social context and presumed functions See above for associations between vocalizations and behavior. Cack is agonistic call associated with threat to territory or self. Chitter is also agonistic but appeasing more than aggressive, usually directed toward close mate, and therefore probably more closely associated with self-defense. Eechip has 2 distinct contexts: in encounters with unmated falcons near eyrie and appeasement in reproductive context. Greater frequency of eechip (reproductive context) by male sug-gests subordinate status relative to female (Carlier 1995). Because Beg imitates young bird, probably functions in appeasement. Copulatory Wail and Whine may also function in appeasement as they are associated with passive postures. Wail, when given by male in absence of mate, appears to function in advertisement. Wail seems to indicate bird is dissatisfied with its current state and is seeking a change (TJC). top NONVOCAL SOUNDS None with a communicative function. BEHAVIOR LOCOMOTION | SELF-MAINTENANCE | AGONISTIC BEHAVIOR | SPACING | SEXUAL BEHAVIOR | SOCIAL AND INTERSPECIFIC BEHAVIOR | PREDATION

LOCOMOTION Walking, hopping, climbing, etc Will walk on ground to approach prey, although most common in young birds. Will walk or run briefly on nest ledge to displace another bird. Incubating adults have trouble walking around eggs or nestlings because feet instinctively ball up as in incubating condition. Male has high- stepping walk used during ledge displays (see Sexual behavior, below). Up to 1 wk prior to fledging, young may wander on foot to 50 m from nest ledge, walking, hopping, or climbing along cliff face. Young also Hop-Run, alternating 2 or 3 steps with a hop during play, or Run- Flap, when encountering obstacles, chasing siblings, or approaching adults (Sherrod 1983). Flight (See additional descriptions under Migration: migratory behavior and Food habits: feeding, above, and Sexual behavior, below). Wings have low camber and relatively high aspect ratio expressed by (female wingspan = 99.7 ± 4.8 cm, wing width = 16.9 ± 0.6 cm [n =14]; male wingspan = 87.1 ± 5.5 cm, male wing width = 14.3 ± 0.7 cm [n =11]; all measurements made on fresh specimens of F. p. anatum, width measured on proximal section of unflattened wing). Wings of F. p. pealei larger but proportionately similar (based on measurements of 2 females, wingspan = 103.5 + 6.4 cm, wing width = 17.7 + 0.7 cm). Wing-tips tapered, slotting limited to distal emargination of inner vane of P10 and P9 (Cade 1982); depth of slotting on P10 is 14.2% of wing-chord, based on 2 museum specimens, 1 male and 1 female (Kerlinger 1989). P9 is longest primary. With exception of Gyrfalcon, Peregrines have heaviest wing-loading of any falcon (0.52 g/cm2 males, 0.66 g/cm2 females, calculated; 0.62 g/cm2 males, 0.59–0.91 g/cm2 females, measured; data in Cade 1982). First-year birds are lighter wing-loaded (and tail-loaded) than older birds, owing to a combination of slightly longer feathers and slightly lower body mass. Lighter loading of immatures may com-pensate for less pectoral muscle development and/or experience. Feathers moderately stiff; feathers of first- year birds more flexible than in adults (Cade 1982). Pectoral mass is approximately 19% of body mass (Hartman 1961) but variable depending on state of nutrition (TJC). Flapping Flight. Normal, cruising wing-beat used during migration and traveling to/from hunting areas. Speed averages 40–55 km/h (Cade 1982, Cochran and Applegate 1986, Ledger 1987, White and Nelson 1991) at a variety of altitudes up to 240 m (White and Nelson 1991). During pursuit, wing-beat becomes deeper and faster (Treleaven 1980, Sherrod 1983), reaching speeds of 112 km/h (Cade 1982, Ledger 1987, White and Nelson 1991, Pennycuick et al. 1994). Pursuit may be direct, as in tail-chasing prey; low-altitude, contour-hugging hunting (including over ocean waves); or approach toward intruders. Flapping used by adult birds when climbing steadily in a helical manner to gain altitude over prey, intruders, or mate. High-intensity flight first observed 2–3 wk after fledging; in young, used almost exclusively to pursue adults (Sherrod 1983). During food solicitation, both fledglings and adult female use a Flutter-Glide, in which wings are held slightly arched below plane of hori-zontal body and manus rapidly flicked back and forth. Tail is fanned, and forward progress is quite slow (Cade 1960, Sherrod 1983). Soaring ( View Video). From Sherrod 1983, except as noted. Static soaring on obstruction currents observed in young within 2 d of fledgling. Wings held open and motio-nless, tail open or closed. Movement is parallel to length of cliff face, within 3–100 m above edge. Dura-tion of several minutes early in fledging period to more than 1–2 h later in dependency. Static soaring on thermals observed in young within 1–2 wk of fledging and intermittently by adults (typically only for minutes at a time) when searching for prey at altitudes of 130–330 m above ground (White and Nelson 1991). In urban areas, static soaring common on thermals produced by buildings and cooling systems (B. Walton pers. comm.). An abbreviated form of dynamic soaring is observed in young within first week of fledging; birds launch themselves from perches, flying down-wind 100–200 m and then turn upwind, using their momentum to return to perch; not a sustained flight. This maneuver may be precursor to Stoop. Stoop. Wings held against body as bird free-falls, typically braking by pulling up or rising abruptly at bottom of dive. Theoretically, Peregrine stooping vertically with closed wings should achieve terminal velocity of 368–384 km/h (228–238 mi/h; Orton 1975); direct measurements (airspeed indicators attached to birds, radar) recorded speeds of 111–144 km/h (66–86 mph; Alerstam 1987, Ledger 1987) in less than ver-tical dives. Estimates made by comparison with mov-ing aircraft range from 160 km/h (matched speed; White and Nelson 1991) to minimum of 280 km/h (passing aircraft; Lawson 1930) but depends on mass of falcon and drag (with minimum drag, 500-g falcon could achieve about 90 m s-1 or 324 km/h, 1,000-g bird, >100 m s-1 or 360 km/h; Tucker et al. 1998). Optical tracking measurements of 3-dimensional paths of stooping Peregrines are consistent with theory (Tucker 1995, V. A. Tucker unpubl.). Calculated stooping speeds, from stationary observers, range from 160 to 440 km/h (Hangte 1968, Mebs 1972, Brown 1976, Hustler 1983). Franklin (1999), a free-fall parachutist, estimated speed and stoop configurations with trained Peregrines that accompanied him from 12,000 ft (3,670 m). At 150 mph (240 km/h), falcon assumed a diamond shape with wings tucked and shoulders slightly extended. In 200-mph (320-km/h) range, falcon pulled wings tight to body and assumed a more elongated position with head slightly extended (hyperstreamlining). High-speed pursuit of prey and execution of stoop require extraordinary visual capabilities. From postural adjustments of head, raptors and falcons appear to use their forward-directed, shallow fovea for near vision (8 m) and their deep, highly acute, laterally directed fovea for distant vision (21 m; Tucker 2000). Having its most acute vision to either side of forward movement causes problem when falcon dives at prey from distance at high speeds, as turning its head sideways to see prey straight ahead may increase aerodynamic drag by factor of 2 and slow it down. Three-dimensional tracks of attacking and stooping Peregrine at its eyrie revealed that falcon avoided this problem by holding head straight and diving along logarithmic spiral path, keeping one eye looking sideways at prey. Even though spiral path is longer than straight approach, theoretical calculations indicate falcon should reach prey quicker following spiral path because faster speed with a straight head more than compensates for greater distance (Tucker et al. 2000). Dives typically executed at angles of 30–60o and from altitudes of 215–320 m; but speeds near terminal velocity require >1,000-m drop. Some stoops may be initiated at distances of >1,500 m from intended target and involve altitude losses of 450–1,080 m. Birds may end stoop by rising abruptly; i.e., braking abruptly at bottom of dive to strike target, or level out as much as 30 m from target (Hangte 1968, Sherrod 1983, Alerstam 1987, White and Nelson 1991). top SELF-MAINTENANCE Preening, head-scratching, stretching, bathing, anting, etc Most complete written description given by Sherrod (1983) under comfort behaviors. Preening behavior begins when nestlings are 6–8 d old (Clum 1995). Preens standing, though fledglings will preen lying. Method of preening flight and body-feathers as in most birds. ( View Video) Toes and talons nibbled with bill, par-ticularly after feeding. Fledglings will allopreen brood-mates (Sherrod 1983); mated pairs will preen and nibble at toes of mates (Cade 1960). Fledglings spend considerable time preening (no quantification; Sherrod 1983). Peregrines typically rouse (shake) after preening; also rouse during flight, particularly after leaving perch (unless to initiate a pursuit). After rousing or preening, may bend head down and to side to rub eye against wing wrist; useful in removing items that stick to eye’s moist surface. Rousing integral part of bathing. Scratching is form of preening for areas not reached with bill; raises one leg in front of wing and bends head down to side; talons (especially middle toe) used to scratch head and bill, effective in dislodging scraps of meat (TJC, NJC). To bathe, approaches water on foot and wades to depth of about 10 cm, about tail base. Wings held slightly out, with all feathers raised; bird crouches and rocks forward, dipping head lightly and quickly in water so water rolls down back and sides; then hops or walks from water. Young show bathing motions in presence of water without bathing; young seen to bath in rain, in high grass wet with dew, and in salt water. Fledglings bathe about once a week. Birds (especially fledglings) may wing-flap and sun-bathe after bathing to help dry feathers. In Yosemite National Park, CA, adults seen to bathe by flying through mist from waterfalls (B. Walton pers. comm.). Has been seen to dust-bathe in arctic Alaska (T. Swem pers. comm.). Sunning consists of perching or lying on ground, with back toward the sun, tail and wings partially or completely spread, often with head turned to side. Sunning may occur without bathing (TJC, NJC). Adults commonly stretch single leg or wing laterally; stand on one leg and stretch opposite leg back to side, simultaneously stretching wing from same side across extended leg. Peregrines also double-wing stretch (warble), bird bends forward and down raising both wings over back, sometimes fully extending wings at wrist; seen more in fledglings; may be followed by wing- flapping (Monneret 1987). Peregrines also yawn and gape. Gaping is stretching mandibles apart briefly, sometimes while leaning head slightly forward; may be repeated every few seconds for up to 10 min (Sherrod 1983); function un-certain, may occur when bird accidently swallows feather-down while preening; sometimes associated with infections of cropworm (Capillaria sp.) but also occurs in healthy birds.

Sleeping, roosting, sunbathing See above for sunbathing. Most detailed descriptions of perched behavior in Cade 1960; Nelson 1970, 1977; and Sherrod 1983. Peregrines sleep/roost/rest in several postures: (1) head forward, both feet down, ( View Video) (2) head forward, one foot tucked up, and (3) head over shoulder, tucked in feathers of back; latter associated with deeper sleep and most frequently at night; both feet may be down or one tucked up. In head-forward positions, head settles between shoulders; eyelids and nictitating membrane usually cover eyes. In very warm conditions, Peregrines may rest with partially or completely drooped wings or with one foot extended forward off perch. In very cold conditions, birds may rest with feathers fluffed, foot tucked completely under breast-feathers, feet may be alternated frequently. Nestlings initially sleep/rest in prone position; be-havior may continue to some degree until independence. Prone position: bird lying on belly, feet tucked underneath; head may be up or forward on substrate. One or both legs may be extended to side to dissipate heat (as in American Kestrel; Bartholomew and Cade 1957); one or both wings may be drooped for the same purpose. Fledglings often roost near each other for first few days after fledging, but thereafter roost independently (Sherrod 1983). Fledglings initially choose new roosts each night, but after several days or weeks, suddenly choose a regular roost. When suitable roosts are few, may roost with adults. Few young return to nest ledge once fledged. Birds hacked in areas without suitable roosting sites tend to return to the hack site to roost. Fledglings may be absent for a day or 2, then return again before dispersing. Roost earlier in day during rainy weather, later during windy weather or when hungry. Fledglings typically leave roost around first light, significantly earlier if hungry. During breeding season, first indication of courtship activity is perching/roosting of male and female on same cliff (Cade 1960, CMW). Eventually pair perches/roosts side by side on same ledge. During incubation, male roosts in a prominent location away from scrape, often on or near top of cliff. After brooding ceases, female does not roost on nest ledge (Sherrod 1983, Carlier 1993). Fledglings may harass adults for food, continued harassment results in adult leaving area, with fledgling sometimes remaining in adult’s roost (Sherrod 1983). Daily time budget For information on incubation and brooding, see Parental care and Breeding: in-cubation, below. Data from Carlier (1993) on F. p. brookei show that during courtship female spent 85% of time in nest’s vicinity compared to 65% for male. Only 15 and 5%, respectively, spent at nest ledge itself. Female attendance to site during incubation remains about the same, but up to 70% spent at nest ledge in association with incubation duties. Male spends comparatively less time in vicinity of nest during incubation (55%) but more time at nest ledge (30%). When eggs pipped, female increased atten-dance at area (100%) and ledge (90%), whereas male decreased attendance (20 and 10%, respectively), possibly because female excludes him (Nelson 1970, Treleaven 1977). Male attendance in vicinity remained constant until young about 40 d, while female attendance to site decreased steadily to about 35% during same period (Carlier 1993). Female attendance at ledge dropped precipitously after 10 d (from 70 to 20% in a 10-d period); after 40 d, she spent almost no time at the ledge. Female attendance to the nest site continued to decrease steadily until about 70 d, when she was present <5% of the time. Male stopped attending ledge sooner (at 20 d) but abandoned area about same time as female (70 d). In Alaskan taiga, there was a clear circadian rhythm of eyrie-area attendance; lowest in early morning (0:00–04:00) and late evening (20:00–24:00) when prey was most active and adults were away hunting (Palmer et al. 2001). Time allocation of wintering birds not quantified. top

AGONISTIC BEHAVIOR Physical interactions Peregrines attack and strike or grapple each other much same way they attack prey (see Food habits: feeding, above). Aerial fights involve stoops, tail-chases, strikes, and rollovers with presentation of talons to attacker; sometimes 2 birds hold onto each other’s feet and cartwheel through air, infrequently falling to ground still bound together (A. Nye in Peterson 1948). On ground, attacker charges in running and flapping and grabs opponent by legs and feet; usually both birds manage to grab hold of each other in some way. Locked together, they jab and bite with bills, directing attack to each other’s head and neck. Vicious and prolonged fights, sometimes lasting hours and resulting in fatal injuries if one bird does not break away soon enough. Occurs most often at eyrie when intruder attempts to replace a breeding bird (Tordoff and Redig 1999b, T. French pers. comm.; see website http://falconcam.apk.net). Such fights also occur during territorial boundary disputes and in squabbles over prey when one falcon attempts to steal food from another. Most fights involving physical contact occur between individuals of same sex; males, smaller than females (see Measurements, below), generally avoid grappling with them. When female fights at eyrie, resident male does not come to aid his mate. Communicative interactions Threat Displays. Threatening postures involve following elements: erection of feathers, turning bill towards recipient of behavior, and gaping or agonistic vocalization (Cade 1982). Erection of feathers may progress from head (especially auricular area) to shoulders, back, breast, and lower body as threats increase in intensity, and may include progressive fanning of tail and holding of wings away from body. Gaping may progress to hissing, Chittering, cacking, or Wailing (see Sounds, above). Orientation toward recipient may progress from static display to strutting, charging, lunging, and grappling. Two general forms of threat display described (Nelson and Campbell 1973, Nelson 1977, Wrege and Cade 1977). Upright Threat consists of vertical orientation of body, feathers erect, wings and tail partially spread, and bill usually open. Horizontal Threat consists of head, body, and tail held in horizontal plane; bill directed toward recipient; wings slightly extended; and head and body feathers erect. See Figure D in Cramp and Simmons 1980 and Figures 6 and 7 in Cade 1982. Because normal, relaxed posture is upright, Upright Threat is generally considered the less intense form. However, when cornered on ground or facing an extreme threat, birds will employ Upright Threat, falling onto back in most extreme cases (Cade 1982). Upright Threat is therefore agonistic yet defensive, whereas Horizontal Threat is offensive. Upright Threat is form most commonly employed by young birds. In captivity, few threat displays observed between mated birds except in new or incompatible pairs (Wrege and Cade 1977). Both forms observed in wild birds during agonistic encounters. Upright Threat also observed during interspecific interactions (Nelson 1977, Cade 1982). Appeasement Displays. Submissive/appeasing postures involve elements that are direct opposite of threat displays, including feathers held tight to body, head held below body axis with bill directed away from recipient, and little or no vocalization (Cade 1982). Most often associated with breeding behavior (see descriptions under Sexual behavior, below). At least in captive birds, relative proportion of agonistic to nonagonistic behavior appears indicative of the stability of pair bond and may be related to degree of sexual dimorphism between mates, large dominant females holding potentially aggressive male in submission (Wrege and Cade 1977, Olsen et al. 1998). top

SPACING Territoriality Nature and Extent of Territory. Cade’s (1960) proposed model, with nesting cliff as center, in general seems fairly accurate: series of threshold perimeters surround eyrie with decreasing defense as distance from eyrie increases. Inner perimeter may be only 200 m; within that, attacks always occur. In outer perimeter, attacks only occur over food or favored perches. Regular spacing of pairs suggests that territory may have minimal average compression distance. Examples from north where densities are high are: Colville River, AK (345 linear km), on average 5.4 km between pairs, closest 0.3 km (T. Swem pers. comm.); Yukon River, AK (linear 265 km), 5.6 km average, closest 1.0 km (R. Ambrose pers. comm.); Nunavat (450 km2), 3.3 km average, closest 0.7 km (Court et al. 1988). Size of territory may be related to prey abundance, and boundary defense may be relaxed or decreased as prey abundance increases (Nelson 1977). Manner of Establishing and Maintaining Territory. Usually uses vocal or physical contact and display advertisement generally classified (Nelson 1977) as Bowing, Horizontal Posture, and Struts (may incorporate tail-fanning as intention movement for flight); Upright or “Griffon” (spreads wing, tail, and body-feathers to increase size); Prominent Perching and soaring (advertisement, particularly in male; the white crop is conspicuous); aggressive flight, strikes, and physical grappling (actual contact, with intruder being held by feet); Power Flight or dive and Undulating Flight (the latter with a roller-coaster motion); Cliff-Racing (repeated rapid passes across cliff face in figure-eight fashion, which is basically advertisement and may be involved in courtship also; see Sexual behavior, below). Can be accompanied with calls phonetically described as: eechup (female), eechip (male), eeyaik, cack, or a series of repeated cacking (see Sounds: vocalizations, above). Patrolling of nesting cliff may take place when adults fly along cliff face or top to a given distance, turn, and repeat course, frequently in leisurely flight. Intraspecific physical conflict over territory or nest can lead to serious injury or death (Hall 1955, Court 1986, Tordoff and Redig 1999b). Such incidents increase with increase in breeding density (Monneret 1987, Ratcliffe 1993, Tordoff and Redig 1997). Interspecific Territoriality. Not easy to separate influence of interspecific territoriality from those of predation and predator defense in interactions be-tween members of different raptor species (see Predation, below). To what extent and how do interactions between raptors of different species modify the spacing of individuals and pairs and their use of resources? Limited studies (Cade 1960, White and Cade 1971, Porter and White 1973, Burnham and Mattox 1984, Poole and Bromley 1988, Ratcliffe 1993, Jenkins 1998) indicate little effect on territorial spacing per se or direct competition for food; but, depending on structure and availability of nest sites (cliffs), individuals of one species can influence choice of nest site by other, heterospecific individuals. Also, possible impact of interference competition on nesting success. Examples: Peregrine seldom nests on same cliff with Golden Eagle but will use abandoned eagle nests; same is true for Gyrfalcon sites, and latter species can prevent Peregrine from using optimum locations on cliffs. Where Prairie Falcon moves into habitat suitable for Peregrine, latter sometimes usurps Prairie Falcon eyries, and vigorously attacks Prairie Falcons passing near eyrie, sometimes killing them. Relations with Great Horned Owl (Bubo virginianus) are inconsistent and puzzling: Some pairs nest close to owls with little conflict; others harass owls at every opportunity and occasionally kill them; but many pairs of owls dominate and drive off or kill neighboring Peregrines, adults and young. Great Horned Owls prevented early attempts of reintroduced Peregrines to reoccupy historical eyries on upper Mississippi River (Tordoff and Redig 1997), and Eagle Owl (Bubo bubo) is credited with limiting nesting distribution of Peregrine in parts of France where cliffs are not num-erous (Terrasse and Terrasse 1969). Peregrine has similar but less threatening relationship with Common Raven (Corvus corax): Interactions between close nesting pairs can be disruptive to successful breeding; but ravens also provide nests that Peregrines use. Winter Territoriality. Year-round resident falcons may remain at nest site, using some displays and vocalizations described above. Often intruders are stooped at, sometimes jointly by pair (e.g., Aleutian Is.) and cack calls given. Migrants to Neotropics may have territorial perches and roosts on nonbreeding (wintering) grounds, male and female often roosting as a couple (although there are no data that such birds are paired; Albuquerque 1984); may even copulate (urban Brazil, coastal Peru, and Ecuador), perhaps an appeasement to lessen territorial strife (J. L. B. Albuquerque, C. M. Anderson pers. comm.). Female shows more territorial aggression toward passing female than toward male (Albuquerque 1984). In California, resident male may courtship-feed and copulate with migrant female, which then leaves in mid- to late Mar to be replaced by local female (B. Walton pers. comm.); also noted in Wisconsin (Tordoff and Redig 1997). Dominance Hierarchies. Not known to occur, but female appears dominant over male (Cade 1960, 1982), and adults may displace immatures. Sometimes immature birds fledged from different eyries tolerated near nesting pairs (B. Walton pers. comm.). Individual distance Pair members often sit side by side, especially noticeable in resident populations. During nonbreeding months (winter), some presumed nonpaired individuals (adults) in Neotropics may roost within 10 m of one another (J. L. B. Albuquerque pers. comm., CMW), while in Palearctic may be found in communal night-time roosts (inter-individual spacing not given; Kelly and Thorpe 1993); may also do so in Americas, as suggested by groups in trees on Dry Tortugas, FL (T. Smylie, J. Weaver pers. comm.). Breeding pairs soaring (even above their eyries) may be joined by another falcon, often coming within 5–10 m of pair. First-year young maintain social groups up to 2–3 mo after nest departure and may start migration together (Cade 1960). top

SEXUAL BEHAVIOR Mating system and sex ratio Monogamous, but at least 3 documented accounts where male provided food to female at 2 eyries simultaneously (R W. Nelson 1990, B. Telford and J. Linthicum pers. comm.), and extra adults at eyries are increasingly frequent with population increase (Monneret 1988, Ratcliffe 1993). In Greenland, overall sex ratio of 1,566 fledglings was 774 males to 792 females (nonsignificant; Restani and Mattox 2000). Sex ratio of captive nestlings 1:1 (C. Sandfort pers. comm.). Pair bond Most detailed descriptions contained in Nelson 1977, Wrege and Cade 1977, and literature summary by Cramp and Simmons 1980. Behaviors described in order of appearance during breeding cycle. See Sounds, above, for descriptions of accompanying vocalizations. Behavior associated with courtship has been seen between nonbreeding adult and mixed adult/juveniles in mid-Oct in Puerto Rico (Meier et al. 1989), s. Florida in winter (TJC), and on the austral nonbreeding grounds (Nov–Mar) in Peru and Brazil (C. M. Anderson, J. L. B. Albuquerque pers. comm., CMW). Also copulations in the Nov–Mar period on nonbreeding grounds. Resident pairs at Morro Rock, CA, seen to copulate every month of year (30 yr observations; B. Walton pers. comm.).

Displays at Nest Ledge. Prominent Perching: perches in conspicuous position near nest ledge (Nelson 1977). May be accompanied by Advertisement Wail. Exhibited more frequently by male, especially before female arrives. Believed to function in mate attraction early in season and also signals site ownership. First indication of pair development is Mutual Perching or Roosting, where male and female perch quietly together (Cade 1960). Progresses from perching on same cliff at some distance to perching side by side. In established pairs, may be accompanied by Peeping, mutual preening, nibbling at toes or bill of mate, or Billing, in which one bird turns its head upside-down and engages bill of the other. Activity on nest ledge increases as courtship progresses. Head-Low Bow is precursor to Ledge Displays, and has 2 forms, with almost complete intergradation between them (see Wrege and Cade 1977 for full descriptions). Less intense Vertical Head-Low Bow is given with body in normal perching position but with head depressed below body plane. More intense Hor-izontal Head-Low Bow consists of crouching with body in horizontal position and lowering head below body axis as much as 90°, with bill sometimes contacting substrate. Bowing of head tends to decrease with increasing proximity to mate. Head-Low Bows performed by either sex in response to movement by or close proximity of mate, and functions in appeasement. Most commonly accompanied by eechip vocalization. Scraping performed by either sex. When Scraping, bird leans forward, placing its weight on breast and vigorously pushes its feet backward, creating small, circular depression as it changes position; no vocal-ization. Usually performed when one sex is alone on the nest ledge.

Ledge Displays are centered on scrape and initially performed by each sex individually, later as pair. Male begins Ledge Displays earlier and displays more intensely than female. Male Ledge Display begins with male approaching scrape in Horizontal Head-Low Bow (see Fig. 1A in Wrege and Cade 1977). Ap-proach is accompanied by eechip vocalization, and in its more intense form may include a high-stepping or tippy-toe gait that produces a side-to-side swagger. Horizontal Head-Low Bow posture and eechip vocalization are maintained at scrape. After 5–10 s, male begins to pause to look at female; any movement by female may elicit renewed activity. Duration of display driven largely by female response. At low intensity, both posture and vocalization degrade. Female Ledge Displays less intense and postures less distinct. Female approaches scrape in less submissive, completely horizontal position, with head sometimes slightly lowered. Approach accompanied by eechup. Female turns in scrape, mandibulates debris, scrapes, but rarely pauses to look at male. Mutual Ledge Displays involve simultaneous Horizontal Head-Low postures and vigorous eechipping by both sexes. See Figure E in Cramp and Simmons 1980 and Figure 8 in Cade 1982. Birds may move around scrape while displaying, may pause, then return to displaying with renewed intensity. Male usually leaves scrape first and lands elsewhere with Hitched- Wing Display. Aerial Displays. Most prevalent prior to egg-laying and after female ceases brooding. Aerial activity begins with High Soaring over and around nest cliff, sometimes accompanied by Advertisement Wail. May be performed by either sex, more typically by male. May be initiated prior to arrival of mate at nest site, therefore probably functions in mate attraction and territorial advertisement. Activity also performed by pair. Cliff-Racing or Figure-of-Eight Flight consists of male flying very rapidly in horizontal plane very close to nest cliff, either in a single pass or back and forth in figure-eight pattern (see Fig. B in Cramp and Simmons 1980). Male also uses Undulating Flight or Loop-the-Loops in vertical plane. Undulating or Z Flight involves level flight followed by a power dive and then a pullout back into level flight or into loop (see Fig. A in Cramp and Simmons 1980). Male aerial displays often involve side-to-side rolling motion of up to 180°, which produces a highly visible flash pattern as the dark dorsal surface and light ventral surface are alternated. Male may end display flights by landing at nest site in a slow, exaggerated, conspicuous manner. Male also flies near eyrie with slow, deep, halting wing-beats and feet extended (see Hitch-Wing Display and Slow-Landing Display, below). Cooperative Hunting begins about the time pair begins perching together (Cade 1960) but year-round in resident California pairs (B. Walton pers. comm.). Behavior progresses from simply hunting in proximity over same range to making passes at same prey. Cooperation typically involves one bird, usually male, making a pass at a flock while the other circles above to stoop on stragglers. Mutual High Soaring may progress into Flight Play, in which one mate stoops at other, and attacked mate rolls over in flight. Birds may present talons, touch breasts, lock talons, or engage bills with mate. Mates also chase or tag each other in flight. Food Transfers. Transfer of food between mates (courtship feeding) may occur on ground or in air, but typically from male to female. Either sex initiates transfer. On ground, female solicits transfers with Vertical Head-Low Bow (see Fig. 9 in Cade 1982) accompanied by a Food Wail. If male has food, female may also use eechup. Alternatively, female assumes posture of Begging juvenile, crouching, spreading tail, fluffing feathers, quivering wings, giving Beg vocalization or perches in fluffed upright posture, and Wails. In absence of food, female may charge male in Horizontal Threat (see Figs. G and I in Cramp and Simmons 1980). Female displays, especially Wail, appear to stimulate male to hunt if he has no food to offer. Male solicitation consists of alternation between normal relaxed posture and bending down to contact or manipulate prey, accompanied by eechip. During actual transfer, male picks up food in bill, standing vertically with head up. Female is typically horizontal with head low and takes prey with bill. Both birds give eechip. Male solicitation may progress from elaborate prey- plucking and conspicuous food-caching to approaching female with food for direct trans-fers. Aggressive or hungry female also forcibly takes prey from male with feet without waiting for ritual transfer. Aerial transfers may be remote, with male dropping food to female as he flies over, or direct, from foot to foot, foot to bill, or bill to bill. Direct transfers involve female rolling over in air to receive prey as male flies directly above her. Female also solicits food during flight with a Flutter-Glide or Sandpiper Flight, essentially an aerial version of juvenile Begging posture (see Fig. H in Cramp and Simmons 1980). Display accompanied by Food Wail. Food transfers develop simultaneously with Ledge Displays. Ground trans-fers to female in Begging posture may predominate up to 2 wk prior to egg-laying (Cramp and Simmons 1980). Copulation; pre- and postcopulatory displays Either sex solicits copulation, female usually later than male. Prior to copulation, male exhibits Hitched-Wing Display, which has both a perched and aerial form (see Nelson 1977, Wrege and Cade 1977 for details). Male may use Hitched-Wing flight (Slow-Landing Display) to access perch or nest ledge prior to copulation or Ledge Display. Upon landing, male typically assumes perched form of display by standing high on stiff legs, hitching wrists of closed wings above back, and holding head low, staring at female (see Fig. D in Wrege and Cade 1977, Fig. 10 in Cade 1980, Fig. J in Cramp and Simmons 1980). Male also high-steps across ledge or perch in Hitched-Wing posture to approach female. If female indicates receptivity by turning away, male adopts a more aggressive posture with body becoming more hori-zontal; posture accompanied by bowing with a side-to-side swing and by Chitter. Elements of solicitation displays may begin 3 wk prior to copulation, with dis-plays typically progressing more to less remote from female. Male may exhibit Hitched-Wing Displays throughout incubation. Female solicitation begins with Vertical Head-Low Bow accompanied by a Whine when male is still at a distance. As male approaches, female assumes Horizontal Head-Low posture perpendicular to or facing away from male with panel feathers raised (see Fig. 1B in Wrege and Cade 1977), accompanied by Whine, and may be held up to 30 s. Mounts either from air or standing position next to female. As male prepares to mount, female sleeks feathers, crouches, and leans forward, and may move her tail up and to side. During copulation, female is at an angle of about 45° with wings slightly lifted and extended (from elbow), sometimes tail partly spread (see Fig. K in Cramp and Simmons 1980, Fig. 11 in Cade 1982). Male maintains upright position throughout copulation by flapping wings high above body and balancing on his tarsi with closed toes and feet turned inward. During copulation, male’s neck is extended and curved; he Chitters while she gives Copulatory Wail. Initially, many mountings may involve incomplete copulations (without full cloacal contact). Completed copulations begin at least 2 wk prior to egg-laying. Duration of completed copulations ranges from about 5 s, earlier in season up to 10 s; normally conducted in close proximity to nest ledge. Copulations continue until third egg laid. Duration and maintenance of pair bond In season, pairs remain together until young have dispersed. Between seasons, estimates of annual turnover range from 17 to 28% for females (Mearns and Newton 1984, Ambrose and Riddle 1988, Telford 1996). Known movements of females to other sites (i.e., divorce) account for 10.3–18% of turnover (Mearns and Newton 1984, Ambrose and Riddle 1988). Strong attachment to nest site (territory) may be main reason mates remain paired from year to year, rather than attach-ment to each other as individuals. Extra-pair copulations A 1.3% extra-pair copu-lation rate was found in dense Canadian arctic pop-ulation, based on minisatellite and microsatellite DNA profiling of adults and broods (R. M. Johnstone unpubl.). Copulations on neotropical, nonbreeding grounds or during northward migration probably do not affect rate, owing to short life of avian sperm and failure to ejaculate. top

SOCIAL AND INTERSPECIFIC BEHAVIOR Degree of sociality Despite solitary mode of existence adopted by most individuals outside breeding season, many breeding and pair-bonding behaviors occur on migration or nonbreeding (wintering) grounds, including neotropical (i.e., Peru, Chile, Brazil); e.g., territories established, birds roosting together, immatures roosting near adult pairs, female food-begging to male, male prey deliveries to female, immatures chasing and food-begging from adults, copulations (Albuquerque 1984; Silva e Silva 1997; C. M. Anderson, C. Gonzales pers. comm.; CMW). One interpretation is that pairs (perhaps family groups) maintain bonds through migration and into nonbreeding grounds; another is that solicitation by appropriate behavior stimulates corresponding appropriate response. Northern migrants wintering in California feed, court, and engage in other interactions with residents in Feb–Mar (B. Walton pers. comm.; see also Spacing, above). Exceptionally 2 fe-males share same nest, despite usual aggressiveness adult females show toward each other. Play Most complete description of play behaviors found in Sherrod 1993. Play occurs mainly in young. Immatures will pursue adults, siblings, prey (both appropriate [vertebrate] and inappropriate [invertebrate]), and attack inanimate objects. Playful Pursuit of siblings begins 2–3 d after first flight, mock combat between siblings begins 4–5 d after. Mock combat progresses from flying parallel and occasionally rolling to extend feet toward siblings, to making short darting dives and grappling in the air, to using air currents to make vertical stoops. Latter develops within 3 wk of flying. Play in falcons may be an expression of joie de vivre or it may simply represent the maturation of neuro-muscular coordination and central control mechanisms involved in agonistic behavior and pursuit and capture of prey. Interactions with members of other species See Spacing, above. Relationship of several species near Peregrine eyries are interesting, especially because Peregrines are thought not to hunt near eyries (e.g., Dement’ev and Gladkov 1951), although in California, fledglings of swallows and swifts nesting on same cliff as falcon are caught (B. Walton pers. comm.), and adults frequently launch attacks at passing birds from eyrie. In many arctic areas, waterfowl (particularly noticeable with Common Eider [Somateria mollissima] in Aleutian Is.) nest in colonylike fashion near base of cliffs housing Peregrines (Turner 1886, CMW). Waterfowl (e.g., Red-breasted Goose [Branta ruficollis] in Siberia (Quinn and Kokorev 2000) and Canada Goose in arctic Alaska (Cade 1960, CMW) may derive protection from falcon driving away potential waterfowl predators (e.g., foxes [Alopex, Vulpes spp.]). top

PREDATION Kinds of predators Adults usually killed only by large avian predators such as eagles, Gyrfalcons, or, at night, Great Horned Owls. Nestlings and immatures subjected to greater array of predators, including other Peregrines; ground nests depredated by mammals (e.g., bears [Ursus spp.], wolves [Canis spp.], foxes, wolverines [Gulo gulo], cats [Felis spp.]). Great Horned Owls and Golden Eagles principal predators on young during reintroduction efforts (Cade et al. 1988, Palmer 1988, Bird et al. 1996); in ne. U.S., owls caused >25% of total mortality (Barclay and Cade 1983). Response to predators See Cade 1960, White and Cade 1971, Nelson 1977, Albuquerque 1984, Palmer 1988. Difficult to give hierarchy of aggression toward other species, but during breeding season, eagles, other Peregrines, Gyrfalcons, Prairie Falcons, and Great Horned Owls are or may be attacked with equal vigor depending on stage of breeding cycle or individual differences in falcons; even herons, large gulls, and jaegers often attacked (Palmer 1988, Bird and Aubry 1982, T. Swem pers. comm., CMW). Golden Eagles attacked at greater distances than falcons or owls: on arctic tundra, incubating female left nest and attacked eagle a measured 1.6–1.8 km away (CMW); at Zion National Park, UT, adult female at eyrie struck passing eagle hard enough apparently to kill or badly damage it, as it fell 184 m and was not seen again (Hays 1987). In central Arizona, adult Peregrine struck head of breeding male Bald Eagle in flight; eagle died days later of apparent concussion (WGH). In Aleutian Is. and coastal British Columbia, where Bald Eagles are abundant, tolerance levels higher, Peregrine sometimes allowing eagle within 200 m of nest. Female pealei in Aleutians struck female Gyrfalcon in air near Peregrine’s eyrie, breaking wing of Gyrfalcon, which was then promptly killed by Bald Eagle (CMW). Species usually given greater tolerance are Com-mon Ravens, Barn Owls (Tyto alba), Rough- legged (Buteo lagopus) and Red-tailed hawks, but first 2 have been killed by Peregrine (Cade 1960, CMW). Both have nested successfully as close as 100 m and 10 m, respectively, although not in direct sight of falcon’s eyrie. Ospreys nested within 200 m (2 nests) directly across water without aggression (J. Crawley pers. comm.). Gyrfalcons and Prairie Falcons nest sympatrically with Peregrines, often as close as 200 m, although in one case, in which nest was about 300 m away, fledgling Prairie Falcons were apparently killed by Peregrines soon after their maiden flight (CMW). Peregrines nesting on ground or low cliffs are more aggressive toward mammals (e.g., bears, badgers [Taxidea taxus], raccoons [Procyon lotor], and canids), than are Peregrines on large cliffs. Kleptoparasitism by Golden and Bald eagles, Rough-legged Hawks, Red-tailed Hawks, Northern Harriers, Gyrfalcons, Common Ravens, and large gulls occurs (Dekker 1995, TJC, CMW) and vice versa. Prairie Falcon fledgling has entered Peregrine eyrie to pirate food (Ellis and Groat 1982), and Great Horned Owl has taken food from hack site without molesting young falcons (H. B. Tordoff pers. comm.).

BREEDING PHENOLOGY | NEST SITE | NEST | EGGS | INCUBATION | HATCHING | YOUNG BIRDS | PARENTAL CARE | COOPERATIVE BREEDING | BROOD PARASITISM | FLEDGLING STAGE | IMMATURE STAGE

PHENOLOGY

Figure 2. Annual cycle of breeding, migration, and molt in the Peregrine Falcon. Note the extreme difference between timing in a northern migrant and a resident population. Thick line shows peak activity; thin line, off-peak. Pair formation Related somewhat to latitude, but pairs at northernmost resident localities remain at eyries, even sitting side by side on ledge in Jan, particularly in locations where sufficient prey occurs (e.g., Aleutian Is.; S. K. Sherrod pers. comm., CMW). Banded birds (usually female) may remain at eyries in some urban areas (e.g., Milwaukee; G. Septon pers. comm.) in midwinter. Courtship and copulation seen in Sierra Madre Oriental, Mexico (where apparently resident) in late Feb (Lanning et al. 1977). Peregrines arrive at nest sites on lower Yukon River, AK, by 15 Apr (R. Ambrose pers. comm.) and Rankin Inlet, Nunavut, by 10 May where both sexes arrived simultaneously (Court et al. 1988). Nest-building No nest built per se. Scraping in substrate begins early in courtship and continues until egg- laying; depending on latitude, 2 wk–2 mo (Nelson 1970). First/only brood per season Figure 2. No record of >1 brood fledged/yr in North America. Because of wide geographic distribution, large range in onset of laying. Latest in Arctic, earliest at southern latitudes; may vary at same latitude depending on conditions (i.e., maritime vs. inland, elevation). In Maryland, earliest record 12 Feb, but usually 25 Mar to 2 Apr (Wimsatt 1940). In s. California, first egg mid- to late Feb; n. California first egg usually in May but replacement clutches as late as Sep (B. Walton pers. comm.). Some dates extrapolated from fledging of young (based on average incubation period of 33 d, average nestling period of 44 d (see beyond and Sherrod 1983). In w. Greenland at 67°N, onset of egg-laying about last week in Jun, farther south at 60°N about 2 wk earlier (21 Jun; Falk et al. 1986). At similar latitude on upper Yukon River, AK (about 65°N), onset 11 May (n = 418 broods; R. Ambrose pers. comm.). In Aleutian Is., about 51°N, first week in Apr (CMW); at Langara I., British Columbia, about 54°N, 28 Apr (Nelson 1977). In San Juan Is., Puget Sound, WA, about 48°N, about 3 Apr, but inland at Seattle, WA, at about 47°N, 3 wk earlier (C. M. Anderson pers. comm.). South- and central- coastal California (about 33–34°N) mid- to late Feb, but at >2,000 m (Yosemite Park region, about 37°50’N) late Mar to mid-Apr (J. Linthicum pers. comm.). At southern edge of range in Mexico (Sierra Madre Occidental), mean laying about 17 Mar, but variable, and young fledge 24 May–4 Jul (Lanning et al. 1977, WGH); onset of laying hard to determine because fresh eggs and 10- to 14-d-old young found at same time in nearby eyries in Baja California (Porter et al. 1988, M. A. Jenkins pers. comm.). Laying interval 48–72 h; interval to last egg longest. Second brood per season None; renesting only (usually within 14 d of egg loss), but no data from southern end of range (Mexico), where presumably also renesting only. May renest 2 or 3 times if clutches removed early in incubation (Bent 1938, Palmer 1988). In California, when young 3 wk old removed from bridges; successful renesting occurred (B. Walton pers. comm.; see also Ratcliffe 1993). top NEST SITE Selection process In some migrants, male appears to arrive at nesting ledge first; in residents, both may remain together in nesting area. Male explores many ledges unless choices limited; then simply makes scrapes on ledge previously used. Usually makes several scrapes, female then selects one for egg-laying (Nelson 1977, Ponton 1983). Same scrape used in Alaska in year following removal of pair from previous year (CMW). During recovery, some currently used scrape areas are same as those used 50 yr earlier (B. Walton pers. comm.; see also Ratcliffe 1993). Microhabitat; nest-site characteristics Varies widely, often geographically, especially because of reintroduction (use of some artificial structures) and natural increase from low numbers. Many first-time breeders in expanding population select nontypical sites. Traditionally nest on cliffs ranging from about 8 to 400 m high; cliffs 50–200 m preferred. Lower size somewhat arbitrary as smaller cliffs merge into category of hillside (Bond 1946, Cade 1960, White and Cade 1971), upper limits often difficult to specify; e.g., nesting on rim of Grand Canyon, AZ (Ellis 1982). On defined cliff, nesting ledge generally one-third way down face (33% on Colville River, AK [White and Cade 1971]; 40% in Greenland [Falk et al. 1986]). Nest platforms include: tops of pingos in tundra; cut for roadbed in Alaska (R. J. Ritchie pers. comm.); Common Raven nests on electric-transmission tower; stone quarry; sugar-factory silo in Idaho; variety of buildings, churches, and bridges in metropolitan centers, usually aided by artificial nest box (Frank 1994, Bell et al. 1996, Cade et al. 1996). In upper Mid-west (Mississippi River, shore of Lake Michigan, and elsewhere), occupied artificial nest boxes frequently placed on power plants (smokestacks or buildings; Septon et al. 1996, TJC). On Pacific Coast of Baja Cali-fornia in Bahía Sebastian Vizcaino, with essentially no relief, some use abandoned Osprey or Common Raven nests on boat-navigation channel markers (towers) about 7 m and 4 m tall (latter surrounded by water at high tide; Massey and Palacios 1994, Castellanos et al. 1997, J. B. Platt pers. comm.). On coastal British Columbia in Sitka spruce (Picea sitchensis) forests under tree roots on hillsides, and in 3 island groups in Queen Charlotte Is., 6 pairs using either abandoned tree nests (as low as 12 m) of Bald Eagle or cormorant (Phalacrocorax spp.) or on broken tree stub in natural cavity (Campbell et al. 1977, 1990; R. W. Campbell pers. comm.); other reports of tree nests from islands in se. Alaska (Van Horn et al. 1982), need verification. In California, Peregrines used deserted Common Raven, cormorant, and Red-tailed Hawk nests on sandy coastal bluffs without cliffs (B. Walton pers. comm.). Orientation varies by latitude or other habitat features, often cliff azimuth may be misleading as eyrie itself may face 90° at variance from cliff. Best cliffs offer updrafts. Sample of eyries (n = 22) on Colorado Plateau had mean azimuth of 101° ± 67 SD, and cliff had mean azimuth of 90° ± 71 SD (Grebence and White 1989). In w. Greenland (about 67°N), eyries face nearly due south; direction thought to be of theromoregulatory value by receiving maximum solar radiation (Falk et al. 1988). In Canada (62°49’N), 69% of eyries faced south or southwest (Court et al. 1988). In warm, arid sw. U.S., 69% of nests cliffs (n = 95) faced some direction of north and east (Ellis 1982, Grebence and White 1989); south- and west-facing nests usually had some boulder or shrub on eyrie ledge to produce afternoon shade. top NEST Construction process On ledges, consists of scraping bowl in substrate, frequently initiated by male, but by both male and female. Falcon lies on breast and pushes feet backward to produce depression (see Fig. 18 in Nelson 1970). Substrate consists of dirt, sand, fine gravel, or sometimes decomposed fecal material or decomposed lining materials of old stick nest. Male may construct several scrapes on same ledge or on different ledges. No material deliberately added, but bones and other debris may be pulled around sitting bird to form circle of material around edge of scrape. Scraping also occurs in stick nests of other birds. Behavior as much courtship ritual as “nest-building” (Wrege and Cade 1977). Structure and composition matter See above. Dimensions Substrate for scrape extremely variable, from small 30-×-30-cm spot on ridge in Arctic to potholes to large 4-×-4-m cavelike structures. Scrape (nest bowl) typically 17–22 cm in diameter and 3–5 cm deep; long-used sites have wider and deeper scrapes than newly formed ones. Microclimate No data. Some nesting scrapes in open on point of land or hillside completely exposed or with limited vegetation screening as in Arctic. On south slopes, in these conditions, female often just shades eggs/small young from heat and sun rather than incubating, and heat stress of both adults and young is evident (Enderson et al. 1973, TJC, CMW). Generally, scrape is in larger ledge with shading, sheltering, or overhangs, and trend to south- or west-facing orientation in high latitudes but more random directions in lower latitudes. Presumably orientation or other micro-features of eyrie protect young from temperature extremes shown in Prairie Falcon (Williams 1984) and Gyrfalcon (Clum and Cade 1994). Maintenance or reuse of nests, alternate nests Considerable attachment to one nest location, but alternates frequently selected on same cliff or within a few kilometers (TJC, WGH, CMW). In California, some pairs moved together to alternate cliffs up to 9 km; with increase in numbers, pairs now each cliff in same year (B. Walton pers. comm.; see also Ratcliffe 1993). Nonbreeding nests None recorded. top EGGS

Peregrine Falcon clutch, collected Battle Creek, Saskatchewan, May 1912; from collections of the Field Museum of Natural History, Chicago, IL. Photo by P. Lowther. Shape Between elliptical and short elliptical. Size and mass From D. W. Anderson, converted from centimeters; SD not available. Data given as length × breadth (mm); a clinal tendency to greater length and volume north to south. Tundrius: Greenland, 51.0 × 41.2, 42.83 (n = 16 eggs); e. Arctic, 51.2 × 40.7, 41.96 (n = 30 eggs); w. Arctic, 52.7 × 40.7, 43.19 (n = 16 eggs). Taiga and temperate Canadian anatum: Maritime, 52.0 × 40.9, 43.04 (n = 81 eggs); central taiga, 52.2 × 40.9, 43.20 (n = 31 eggs); w. subarctic, 52.2 × 40.9, 43.20 (n = 50 eggs). Pacific Northwest pealei: 53.7 × 41.3, 45.32 (n = 130 eggs). W. U.S. anatum: Pacific Northwest, 53.1 × 42.0, 46.35 (n = 99 eggs); s. California, 52.9 × 41.2, 44.43 (n = 586 eggs); Baja California, Mex-ico, 53.1 × 41.1, 44.38 (n = 105 eggs). Central and e. U.S. anatum: Great Plains, 53.4 × 41.7, 45.95 (n = 133 eggs); Great Lakes region, 54.1 × 42.0, 47.22 (n = 49 eggs); e. U.S., 53.9 × 41.6, 46.15 (n = 399 eggs). Egg mass at laying in captive falcons about 45.5–47.3 g, but loses about 0.17 g/d; averages 16.3% loss of mass to hatching (Burnham 1983). Eggs produced in captivity smaller than wild eggs. Color and surface texture Fairly smooth without gloss. When fresh, ground color varies from pale creamy to brownish or reddish overlaid with dots, spots, and blotches of various warm browns to deep reds and purples; great variation. Generally deeper and richer color than other large North American falcons. Eggshell thickness Within-clutch variation (cap-tive-laid eggs) may account for 67% of variation while between- clutch thickness accounts for 26% of variation (Burnham et al. 1984). Degree of thinning resulting from chlorinated hydrocarbons (DDE) varied from region to region, but onset of reduced productivity usually associated with population averages of >18% thinning. In sample of California eggs, 201 prethinning eggs had mean thickness of 0.365 mm ± 0.049 SD; 287 eggs 1978–1985, mean thickness 0.300 ± 0.0174 SD (L. F. Kiff pers. comm.). During DDT era, mean shell thickness in North American populations decreased by 12% in Queen Charlotte Is., up to 29% in New Jersey; other known populations with decreases >18% occurred in Arctic and interior Alaska, Ungava in Quebec, Colorado, Rocky Mtns., and California. Worldwide lowest de-crease recorded in Australia (>5%), but none of 30 sampled populations showed no shell-thinning in that period (see Cade et al. 1988, Ratcliffe 1993, and Johnstone et al. 1996 for reviews of eggshell-thinning in relation to pesticide contamination). For large sample of pre-DDT western anatum (n = 573 eggs; L. F. Kiff pers. comm.): mean shell thickness 0.365 mm ± 0.023 SD (range 0.311–0.434; SE of mean 0.002) and shell mass 4.26 g ± 0.394 SD (range 3.253–5.502; SE of mean 0.032). For a sample of pre-DDT eastern anatum (n = 94; Anderson and Hickey 1972), shell thickness was 0.375 mm. Clutch size Clinal, with smaller mean of 3.0 in Arctic (although quite variable; perhaps function of weather and thus food) to 3.72 in midlatitudes; then smaller (3.3) again southward into Mexico; slightly larger clutch size in Aleutian Is., with mean of 3.8 (mode of 4.0; CMW). Occasionally 5 or 6 eggs; in 1.0% of 282 clutches (Hickey 1969, Palmer 1988). Egg-laying First-time layers start later in breeding season (Nelson 1977). Female becomes lethargic about 5 d before egg-laying. Interval between eggs about 48 h, but may be >72 h. In temperate latitudes, at least, clutch may be replaced in about 2 wk if first clutch lost. In captivity, by removing clutches as laid, a female may lay up to 16–20 eggs (TJC, cited in Palmer 1988), or 12–16 eggs if taken one by one as laid (Weaver and Cade 1991). In California, 4 complete clutches removed from same female by egg collectors (B. Walton pers. comm.). top INCUBATION Onset of broodiness and incubation in relation to laying In temperate latitudes usually begins with penultimate egg, but in high latitudes and cold climates may begin after first or second egg, depending on conditions, with staggered hatching (Court et al. 1988). Incubation patches Both sexes have paired lateral brood patches. Less well developed in male. Belly area may function as patch also but less edematous and vascular than breast (TJC). Incubation period According to A. Hagar (in Bent 1938), 33–35 d, not 28–29 d, as commonly stated. Based on captive falcons, about 33.5 d (range 33–34, n = 42; Burnham 1983). Direct observation of identified eggs in wild near San Francisco, CA, was 37 d (B. Walton pers. comm.), possibly related to long or frequent periods of interrupted incubation. Mean hatching dates related to latitude or temperature. At Thule, Greenland (76–77°N), hatching estimated 9–13 Jul (young 17–21 d old on 30 Jul; W. Burnham pers. comm.). In w. Greenland at about 67°N, 14 Jul; in s. Greenland at about 60°N, 4 Jul (Falk et al. 1988). At 62°N, in Nunavat, mean hatching 9 Jul. At mid-latitudes, in Puget Sound, WA (about 49°N), lays 3–7 Apr while inland at Seattle, WA (about 47°N), starts 3 wk earlier (C. M. Anderson pers. comm.). Near southern edge of range in Mexico (continental and Baja California), hatching date late Apr (Lanning et al. 1977, Porter et al. 1988); 1 nest in Cuba had estimated hatch date of about 1 Apr, laying about 18–19 Feb (based on 2-wk-old chicks on 14 Apr 1999; Regalado and Cables 2000). Parental behavior Based on 4,200 film-h (70,000 frames) in interior Alaska, males incubated about 33% of time, with attentive periods of 2–3 h; female attentive period was about 4 h (Enderson et al. 1973); in same region, adults attended at ledge 99% of time (n = 24 nests) until young 11 d old, then most ledge visits were to deliver food or feed young (Palmer et al. 2001). Nelson (1970) suggested that for the Pacific Northwest male, incubation was 30–50% of the time. Extreme in New Mexico was male incubating as much as 87% of daylight period (average 63% for 18 d) and female as little as 12% (average 37% for 18 d; Clevenger 1987). Adults change position about every 30 min and may shift eggs then (Enderson et al. 1973). Parents seen moving displaced egg into nesting scrape by rolling it with bill (H. B. Tordoff pers. comm.) and frequently move young by picking them up by the nape to transport them. Hardiness of eggs against temperature stress; effect of egg neglect Higher than normal egg temperatures during early incubation cause early fatality, whereas lower than normal at that time cause late embryo fatality. Low temperatures late in incubation have less effect; eggs may hatch at higher or lower than optimal body temperature (about 37°C), but such embryos frequently show abnormalities (Burnham 1983). Even advanced eggs can remain uncovered for several hours without injury to embryo; frequent interruptions of incubation result in longer than normal incubation (TJC). top HATCHING Preliminary events and vocalizations Few data from the wild. From blind near eyries on coastal British Columbia (F. p. pealei), Nelson (1970) could hear chick peeping inside egg before hatching began, becoming louder during hatch; initial pip of shell occurred >72 h before chick broke free completely. In artificially incubated eggs, 24–48 h before pip, air cell in egg expands and starts extending down one side of egg toward narrow end; normally chick makes pip inside air cell. In 500 artificially incubated eggs of F. p. anatum, mean time from pip to hatch was 47.8 h (range 11.8–84.8, mode 48; data from C. Sandfort and The Peregrine Fund archives). During this period, chick periodically works to break up area around initial pip but rests most of time. Human imitation of parental chip call stimulates chick to vocalize (Weaver and Cade 1991). Shell-breaking and emergence Often chick creates an opening in break-up area around pip before final breaking open of shell begins; then, looked at from blunt end of egg, chick makes a counterclockwise turn inside shell, at same time breaking a line around circumference of egg near blunt end by thrusting egg tooth against shell. Chick turns intermittently, breaking a portion of shell with much vocalization, then rests, and turns again. This last stage of hatching takes 15–60 min (Burnham 1983, Weaver and Cade 1991). Artificially incubated eggs hatch most frequently during morning hours: 40% of 500 eggs found hatched between 06:00 and 12:00; 24% between 12:00 and 18:00; 19% between 18:00 and 24:00; 17% between 24:00 and 06:00 (The Peregrine Fund data files; values somewhat biased toward morning and afternoon hours by times of observation). Eggs generally said to hatch synchronously (i.e., 24–48 h for clutch of 4) in temperate and low-latitude regions, incubation beginning with last or penultimate egg (Ratcliffe 1993). On Yukon River, AK, 1 clutch of 4 eggs hatched at intervals of 10, 60–72, and 110 h, for total hatching time of about 7.5–8 d; last-hatched chick from this and 1 other asynchronous hatch died in few days (Enderson et al. 1973). At Rankin Inlet, Nunavut, staggered hatching was prevalent and associated with 7% decrease in brood size (Court 1986); about half of last- hatched young in broods of 4 died (Court et al. 1988). Beginning incubation before penultimate egg and staggered hatching likely at high-elevation nests, too, as incubation early in laying cycle appears to be response to cold temperature. Parental assistance and disposal of eggshell Adults may remove eggshells and sometimes eat them (NJC). Some shells may remain in nest several days until presumably broken or accidently knocked from nest. Addled eggs remain in nest until ultimately crushed. Some intact eggs from previous year may be found in eyries (NJC). top YOUNG BIRDS Data herein from Palmer 1988, Marchant and Higgins 1993, and Clum et al. 1996. Condition at hatching Semialtricial, nidicolous; covered with off-white (prepenne) down; bill and feet pinkish to pale gray; eyes closed; mass 35–40 g. If eyes open with food-begging first day, they are slitlike. Obtains 2 downy plumages. Growth and development Five days after hatch, mass has doubled, sits with relative ease, and open eyes more round. At 6–8 d, second down (mesoptile or preplumulae) starts to emerge, first on humeral and alar tracts but no down visible on belly at 6 d, although on legs and belly at 8 d; also second down well out on wings and sheaths of primaries breaking skin on wings. By 10 d of age, second down complete and uniform and outer rectrices breaking skin. At 10 d, primaries growing at 2–3 mm/d, rectrix sheath not yet split. At 14 d, second down dense and long, rectrix sheath about 2 mm and typically ninth primary emerges from sheath. By d 17, contour feathers start to push out prepennae and only pale (buffy) tips of rectrices have emerged but growing at about 2 mm/d (since day 13). At 20 d, while still with heavy coat of second down, contour feathers visible on margins of wings, tail, and faintly around eyes. By 30 d, young appears about half down-covered and half feathered; while side of face well feathered, crown still covered with down. At 35 d, while mostly feathered, large conspicuous patches of down around legs, under wings, and on crown. At 40 d, almost fully feathered with traces of down on crown and under wings and outer several remiges; rectrices not fully grown but bird capable of weak flight. Formula for age (d) of nestling at any stage of development: (Wing length in cm + 0.84)÷ 0.69 (NJC). Onset of thermoregulation variable, may be dependent on climate, but once full feather coverage (not fully grown), perches alone at night. In Greenland, young began to wander out of nest scrape proper ≥10 d after hatching, but most of time spent there until 24 d, after which time also less bodily contact with one another (Hovis et al. 1985). top PARENTAL CARE Brooding Begins during hatching; young brooded >80% of time in Greenland up to age 10 d; amount gradually decreased to 20 d; not brooded thereafter (Hovis et al. 1985). Feeding In Greenland, time adult spent feeding young about 9% to 5 d of age, about 3–9% to 20 d. Food delivery rate ranged from 1/43 to 1/75 min to about 20 d of age and length of feeding bouts ranged from about 3.0 to 6.7 min/bout to 20 d (Hovis et al. 1985). In Alaskan taiga, A. G. Palmer, D. L. Nordmeyer, and D. D. Roby (pers. comm.) found delivery rates/nestling declined with increase in brood size in broods of 1–3 but not between broods of 3 and 4. On biomass basis, mean delivery rate/brood ranged from about 20 g/h in broods of 1 to 60 g/h in broods of 4. New hatchlings fed only on muscle without bone; diet same as that of adult after 2–3 wk (see Food habits: diet, above). View Video. Nest sanitation Young in first few days of life simply squirt excreta, but after several days, defecate by backing away from center of scrape, bending forward as if stretching, and directing a stream of uric acid and fecal material away from scrape. Use of traditional ledges can cause excrement and nesting debris to become several meters deep over time; dating of debris (Australia) suggests some debris and excreta as old as 16,000 yr (Olsen 1995). Adult removes some material (e.g., old carcasses) with bill from ledges. Carrying of young See Incubation, above. top COOPERATIVE BREEDING Rare under normal population structure. Two females at Reelfoot Lake, TN, reported to incubate same clutch alternately (Spofford 1947b); also ob-served in 2001 at building site in Edmonton, Alberta (G. Court pers. comm.). On Langara I., British Colum-bia, 1 female paired with 2 males, but 1 male did not transfer food or copulate; observations suggested female behavior by pairing with second male was aimed only at holding his territory in addition to her own (Nelson 1990). top BROOD PARASITISM Not known to occur. One case of Peregrine on Colville River, AK, incubating 3 of its eggs in Rough-legged Hawk nest that also contained 2 eggs of that species. Only male Rough-legged Hawk was present near nest; Peregrines may have killed female to usurp nest (J. H. Enderson and CMW unpubl.). D. Anderson found Prairie Falcon reared by Peregrines in Gulf of California, Mexico (B. Walton pers. comm.). top FLEDGLING STAGE Within 10 d of first flight, young pursue adults to solicit food. Flight progresses from Butterfly- Flight (1–2 d after first flight) to Flutter-Glide (3–9 d) to Powered Flight (15–25 d). Butterfly- Flight appears to be weaker form of Flutter-Glide associated with in-complete development of flight feathers and pectoral muscles. Pursuits gradually become more sustained and range farther from nest cliff. Adult pursuit is accompanied by Begging vocalization. During first 2 wk of flight, young birds’ pursuit of parents takes precedence over most other activities. Young will even pursue parents during territorial defense (Sherrod 1983). As young become more aggressive toward food-delivering parents, adults sometimes begin to drop both dead and live birds in air. Young pursue and catch these items. Has been interpreted as parental training of young to hunt, but may simply be way for parents to avoid being mobbed by hungry young (Sherrod 1983). In migratory populations, dependency may con-tinue until onset of migration 5–6 wk postfledging. Period of dependency longer in nonmigratory pop-ulations (9–10 wk postfledging). Some level of parental feeding occurs during this time. Dispersal of hacked birds occurred (on average) after 30 d and 33 d on the wing for the male and female, respectively. Most hacked birds had dispersed by 6 wk after fledging, though records of later dispersal exist (58 d, 75 d, and 237 d postfledging); also, some young disappearing in first week after fledging later found breeding (TJC). Timing of dispersal may be related to level of food provisioning to hacked and wild birds. Adults observed to become aggressive toward offspring late in dependency (Sherrod 1983). top IMMATURE STAGE Groups of immatures on migration are suspected of being siblings (Cade 1960, Sherrod 1983). Sherrod also cites 5 instances of immatures begging from adults on migration and 4 occasions where migrating adults allowed immatures to take food from them. Assumption of these observations is that offspring would beg only from their parents and only parents would allow offspring to rob them of food. However, food-begging by first-year birds and giving of food by adult to first-year birds have been seen in Jan and Feb in neotropical nonbreeding grounds (J. L. B. Albuquerque pers. comm.). Some year-old young tolerated at breeding sites in California and unrelated year-old young beg food from breeding adults (B. Walton pers. comm.). top DEMOGRAPHY AND POPULATIONS MEASURES OF BREEDING ACTIVITY | LIFE SPAN AND SURVIVORSHIP | DISEASE AND BODY PARASITES | CAUSES OF MORTALITY | RANGE | POPULATION STATUS | POPULATION REGULATION

MEASURES OF BREEDING ACTIVITY Age at first breeding; intervals between breeding Annual breeding. Age varies, depending on territory availability, the latter influenced by floater com-petition and breeder turnover. Female tends to breed year earlier than male (Cade and Fyfe 1978, Ratcliffe 1993). Breeder age distribution skewed to younger individuals in depleted or expanding populations or when not otherwise density limited (Tordoff and Redig 1997). Mean recruitment age of 16 males in an increasing population in Nunavut was 4 yr (range 2– 8), 3 yr for 4 females (range 3–5; Johnstone 1998). In midwestern population, also increasing, most individuals of both sexes bred at 2 yr, but twice as many females bred at 1 yr and 10 times more males than females first bred at >3 yr (Tordoff and Redig 1997). Yearling female more frequent as pair member than yearling male, although both sexes have bred successfully as yearlings (Wendt and Septon 1991). In captivity, mean age of first breeding of 21 females was 3.4 yr ± 1.15 SD (range 2–5; Clum 1995). Of 22 wild-taken males in captivity, 5 first copulated at 3 yr old, 9 at 4 yr, 3 at 5 yr, 2 at 6 yr, and 3 at 7 yr (mode 4 yr, mean 4.2 yr); of 30 females, 2 first laid at 2 yr, 10 at 3 yr, 12 at 4 yr, 4 at 5 yr, 1 at 6 yr, and 1 at 9 yr (mode 4 yr, mean 3.9 yr; Cade and Fyfe 1978). Clutch See Breeding: eggs, above. Annual and lifetime reproductive success Annual Success. Best characterized by recent data (Appendix 1). Breeding success (percentage of nests fledging ≥1 young) and productivity (number of fledged young/territorial pair) varied greatly from region to region and year to year in decades of 1970s–1990s as populations recovered from effects of pesticides on reproduction. Prior to 1980s, declining or greatly diminished populations generally characterized by depressed annual productivity rates of <1.0 to <0.5 fledglings/territorial pair (Cade et al. 1988, Ratcliffe 1993); continued in Colorado into 1980s (Appendix 1), but after 1984, in association with massive reintroductions, breeding population dramatically increased there and annual productivity from 1985 to 1998 ranged from 1.2 to 1.9 young/pair (mean 1.6, n = 395 pair-yr; G. Craig and J. H. Enderson in Mesta 1999). Similar but less severe pattern in California (Linthicum and Walton 1992); by 1993–1997, annual productivity there ranged from 1.4 to 1.7 young/pair (mean 1.6, n = 356 pair-yr; Mesta 1999). Other factors influencing annual productivity include: (1) egg and chick mortality from cold, wet, and late spring weather, a major factor (Cade and White 1971, Court et al. 1988, Mearns and Newton 1988, Ratcliffe 1993); (2) local yearly variation in prey abundance (Court et al. 1988); (3) regional differences in overall prey availability (Ratcliffe 1993); in 6 eco-regions of ne. U.S. from 1984 to 1996, productivity varied from 1.12 to 1.81 young/pair and nesting success from 59 to 93% (n = 332 pair-yr), apparently related to prey availability (Corser et al. 1999); (4) predation/disease: not quantified for any population but can be locally significant; e.g., Great Horned Owls prevented at least 8 pairs from establishing successful nests on cliffs of upper Mississippi (Cade et al. 1989, Tordoff and Redig 1997); owl and Golden Eagle depredations often main cause of deaths among hacked young in reintroduction programs (Barclay and Cade 1983, Cade et al. 1988). Difference in productivity at individual territor-ies within local population is notable characteristic of Peregrines. At Rankin Inlet, Nunavut, at regularly occupied (high-quality) sites, productivity over 14 yr averaged 1.4 young; at infrequently occupied (poor quality) sites, 0.8 young/pair (Johnstone 1998; see also Mearns and Newton 1988 for similar findings in Scotland). In coastal British Columbia, half of all nestlings produced by 21% of nesting pairs, one-quarter by just 9% (R. W. Nelson pers. comm.). In Massachusetts, 1935–1947, pairs at 6 superior eyries (based on physical characteristics) produced >76 fledglings, while pairs at 8 inferior sites produced only 27 young (Hagar 1969). In Scotland, both cliff height and accessibility of nest ledge positively correlated with number of young produced (Mearns and Newton 1988). Also, immature females on average have reduced reproductive performance (Mearns and Newton 1984) and often fail to lay eggs (Ratcliffe 1993). Generally, <50% of breeders produce >70% of young in local populations. Lifetime Reproduction. Few data; needs study. Partial lifetime reproductive success reported as follows: (1) male on Langara I., British Columbia, raised 22 young in 7 yr; female, 18 young in 8 yr, but females consistently producing more young reported to have had lower survival than birds producing fewer young/yr (Nelson 1988, 1990). (2) Female on Yukon River, AK, raised 3–4 young/yr for 7 yr (White et al. 1995). (3) falcon on Sun Life building in Montreal, Quebec, produced 22 young over 17 yr with 3 different males, close to lifetime record (she lost clutches to egg breakage in 3 yr after 1947 and had no place to make scrape in first 2 yr of occupancy, so effective breeding career was 12 yr; Hall 1955). (4) In midwest U.S., of breeders that died early, 31 males with average age of 4.0 yr at death raised 143 young (4.6 per male); 18 females dying at average age 2.7 yr fledged 75 young (4.2 per female); 9-yr-old female produced 25 of those young before being killed by another adult female; 31 males still living at average age 4.6 yr had already produced 238 young (7.7 per male) and 36 living females with average age 5.1 yr had fledged 355 young (9.9 per female); 4 of those females aged 9, 9, 9, and 7 yr fledged 87 young (25% of total; Tordoff and Redig 1997). (5) At Rankin Inlet, falcons at frequently occupied eyries had mean breeding life span (i.e., site tenure within study area) of 2.7 yr (range 1–5, n = 39) for male and 2.9 yr (range 1–5, n = 65) for female, with mean lifetime production of 4.7 young (range 1–11, n = 65); at infrequently occupied eyries mean breeding life span for male was 2.0 yr (range 1–4, n = 9), for female 2.2 yr (range 1–4, n = 15), with mean lifetime production of 3.0 young (range 1– 10, n = 18; Johnstone 1998). Difference in perceived breeding careers in Arctic and Midwest may reflect differences in site tenure rather than mortality; most Midwest breeders held territories year round, whereas arctic falcons must annually reclaim them, a difference possibly increased by annual variations in suitability of arctic nesting territories (see Population regulation, below). Reproductive Success in Captivity. Female age has significant effect (p = 0.0001) on all measures of reproductive success: clutch size, fertility, hatchability, brood size, nestling survivability, and number of fledglings; in all but 1 case (nestling survival), data best fit quadradic model, reflecting initial increase in performance followed by decrease with age; females that retained mates throughout lifetimes had higher annual fertility, hatchability, and brood sizes at hatching and fledging than females changing mates ≥1 times, suggesting selection in nature should favor lifetime monogamy; changing breeding locations of mated pairs had no influence on breeding performance. Similarity of reproductive patterns between wild and captive birds, not limited by access to mates, nest sites, and food or subject to environmental hazards, suggests age-related changes in reproduction are not necessarily resource-limited; in the absence of resource limitation in captivity, experience of the pair is primary factor determining reproductive success, but benefits of increasing experience are eventually offset by senescence (Clum 1995). top LIFE SPAN AND SURVIVORSHIP Maximum longevity records for banded birds range from 16 to 20 yr. Nestling female banded on Colville River, AK, in 1981, trapped alive and released in California, Sep 2000 may be oldest, >19 yr (T. Swem, B. Walton pers. comm.); male hacked at Cobb I., VA, in 1978 found dead at James Bay Bridge, VA, in Apr 1995, <17 yr (J. Barclay pers. comm.); also famous Sun Life female in Montreal disappeared after >18 yr. In captivity, few live beyond 20 yr; maximum up to about 25 yr (TJC). First-year survival not well known but now generally assumed to be 40–50% of fledglings (see Ratcliffe 1993 for higher estimates in Britain). No reliable estimate of first-year survivorship in any North American population; estimated minimum of 23% in midwestern F. p. anatum based on resightings of marked birds (Tordoff and Redig 1997), but actual survival must be higher. Beebe (1960) proposed that survival among first-year F. p. pealei was low due to harsh maritime environment. Minimum breeder survival in F. p. pealei estimated at 63% for female, 74% for male, based on observed turnover rates (using sketches of physical differences of individuals); females producing large broods were more frequently replaced (Nelson 1988, 1990). Data on turnover rates of banded falcons corrected for breeder dispersal indicated 91% survival for breeding female Scottish Peregrines (89% for both sexes combined; Mearns and Newton 1984). Based on photo-graphs of individual facial markings (primarily), minimum breeder (F. p. anatum) survival (turnover cor-rected for off-site encounters) calculated at 84% (n = 57) in Colorado during 1981–1985 (Enderson and Craig 1988). Based on corrected turnover rate of banded females (n = 40), minimum survival 77% on Yukon River, AK, 1981–1984 (Ambrose and Riddle 1988). Minimum of 81% annual survival estimated for breeding female F. p. tundrius and 85% for males, based on a marked population in Canadian Arctic (Court et al. 1989). In same region, Johnstone (1998) estimated annual survival (from turnover) of 74% for male (80% if adjusted for known breeder dispersals) and 69% for female (76% adjusted). Using capture-recapture method, Gould and Fuller (1995) estimated minimum annual female breeder survival of F. p. tundrius in Greenland 1983–1991 at 79%. Based on band identifications and voice-printing, Telford (l996) estimated 18% turnover of females at 11 eyries (possible range 16.7 to 25.0%) in ne. U.S. from 1989 to 1991, or 82% minimum survival. From 1987 to 1995 in midwest U.S., territorial adult survival of males based on 115 male territory-yr varied annually from 71 to 89% (average 79%), and for females based on 136 female territory-yr range was 80 to 100% (average 93%), highest reported for any population; difference between sexes highly significant (Tordoff and Redig 1997). Theoretically, where adult survival = 70%/yr, assuming no change with age, median adult life (after second year) is about 2 yr (mean 2.8 yr), at 10 yr 3% of cohort still alive, and about 0.1% survive to 20 yr; for 80% rate, median >3 yr (mean 4.5), 11% alive at 10 yr, 1.0% at 20 yr; for 90% rate, median >6 yr (mean, 9.5), 35% alive at 10 yr, 12% at 20 yr. Arctic migrants fall in range of 70–80% minimum adult survival; resident, temperate zone birds, in range of 80–90%, with possible exception of falcons on Langara I., British Columbia (Nelson 1988, 1990). Known population growth rates in recent years and well-known pro-ductivity rates indicate true adult survival rates for migrants likely fall in range of 80–85% and for residents in range of 85–90% (see Population regulation, below). top DISEASE AND BODY PARASITES Peregrines harbor numerous organisms: avian pox (Poxvirus avium), Newcastle disease, herpesvirus, various mycotic infections, strigeid trematodes, air sac nematodes (Serratospiculum amaculata; particularly common in falcons of arctic origin), malaria (Plasmodium relictum), tapeworms, various bacterial organisms of at least 13 kinds (e.g., Proteus, Escherichia, Enterobacter, Staphylococcus, Streptococcus, Pasterella, Pseudomonas, Proteus, Salmonella). Have suffered mortality from Clostridium botulinum Type C and Trichomonas gallinae acquired secondarily from prey (Cooper et al. 1980, Fowler 1986). Various ectoparasites (e.g., hippoboscid flies and mites). Also 4 species of Phthiraptera (“chewing lice”; Colpocephalum zerafae, Degeeriella rufa, Laemobothrion tinnunculus, and Nosopon lucidum; D. Clayton pers. comm.), the Siphonaptera (Ceratophyllus garei), and dipterans (Icosta nigra, Ornithoctona erythrocephala; Wheeler and Threlfall 1989). top CAUSES OF MORTALITY Fledglings at cliffs may be killed prior to independence by other raptors, especially Great Horned Owls and Golden Eagles, occasionally by mammalian predators, and also suffer disease and accidents. Urban fledglings may have greater variety of postfledging fatalities than fledglings in natural landscapes; deaths primarily from collisions with automobiles, windows, and other human-made objects, and drowning after falling from bridges (Cade and Bird 1990, Sweeney et al. 1997). Collisions also affect older age classes; in nonurban environments, face a variety of human-related hazards, including electrocution by utility lines, wire and fence collisions, shooting, and airplane strikes (Barclay and Cade 1983, Santa Cruz Predatory Bird Research Group unpubl.). In total of 455 recorded fatalities among midwestern Peregrines, 78 caused by collision with buildings, 50 by vehicle collisions, 33 by miscellaneous accidents, 28 by disease and starvation, 19 by adult Peregrines, 15 by predators, 10 by shooting, and 10 by storms and lightning and lesser numbers of other causes (Tordoff et al. 2000). Territorial rivalry, including actions on winter territories, between adults may result in death, increasingly so as breeding density and floaters in-crease (Herbert and Herbert 1965, Tordoff and Redig 1999b, R. E. Ambrose and P. Pyle pers. comm.). top RANGE Initial dispersal from natal site In reintroduced eastern population, natal dispersal of 29 females ranged from 0 to 752 km, with 18 (62%) >100 km; for 13 males, 0–1,117 km, with 8 (62%) >100 km (Barclay 1995). Female generally disperses farther than male from natal localities to breed. In upper Midwest, 67 females moved on average 345 km and 73 males, 174 km; but direction was random (Tordoff and Redig 1997); 75% of females nested 355 km and 75% of males 170 km from natal areas (Septon et al. 1996). In Alaska, average distances were 121 km for 20 females and 69 km for 66 males (Ambrose and Riddle 1988). Of 1,702 nestlings banded from 583 broods in Greenland, only 35 males and 7 females were recruited as breeders back into study area; natal dispersal of 21 males was 28.1 km, and for 6 females, 27.1 km. One female banded in 1990 found breeding in 1997 about 690 km from natal site (Restani and Mattox 2000). Females had a higher mortality rate (12 males to 33 females recovered), suggesting that proportionately fewer natal females were available for return and recruitment. Fidelity to breeding site and winter home range High degree of nest-site fidelity among F. p. tundrius in n. Canada, where only 1 of 26 resighted females and none of 16 males moved in following year (Court 1986). In Alaska, only 2 of 40 resighted females moved to new territories in different drainage (Ambrose and Riddle 1988). In Colorado, only 3 of 48 resighted (F. p. anatum) moved to other territories in following year (Enderson and Craig 1988). In reintroduced midwest population, of 241 territory-yr through 1995, only 10 involved adults moving to new territory: 7 left territories where breeding was unsuccessful or mate disappeared, 4 where bird left successful site for better one, and 3 associated with eviction by fighting (Tordoff and Redig 1997). Female more likely to switch breeding sites than is male. In Porto Alegre, Brazil, during boreal winter, birds (unbanded but identified by morphological traits) on same territory several years (J. L. B. Albuquerque pers. comm.); banded resi-dent California falcons show great territory fidelity in winter (B. Walton pers. comm.). Fidelity to territory (eyrie) probably accounts for durability of pair bond (Cade 1960, Tordoff and Redig 1997). Home range Defined here as hunting range beyond defended boundary around eyrie. Extent of home range movements by territorial pairs during breeding reflects prey density (Ratcliffe 1993). With radio telemetry in Colorado, Enderson and Craig (1997) estimated mean home range during nesting of 358–1,508 km2 for 2 adult males and 3 adult females. In relatively prey-rich habitat of Scotland, as little as 117 km2 (Mearns 1985). In Channel Is., CA, breeders with radio transmitters foraged primarily within a 5 km of breeding cliffs (WGH); also on Queen Charlotte, I., British Columbia (Beebe 1960, Nelson 1977). Of hunting flights of breeding female within home range in n. California, 47% >1 km; for male 65% >1 km; hunted on average 5 km (range 3–8) from eyrie (Enderson and Kirven 1983). Winter ranges of 7 telemetered Peregrines in coastal Texas, most overlapping, were 20–28 km in diameter; adults more sedentary than first-year birds (Enderson et al. 1995b). top POPULATION STATUS Numbers Lower densities in North America compared to Europe (Ratcliffe 1993); among Holarctic and Nearctic falconiforms, only Gyrfalcon and prob-ably Prairie Falcon have smaller total populations in America (Clum and Cade 1994, Steenhof 1998). In late 1990s, North American breeding populations increasing at 5–10%/yr (Enderson et al. 1995a, Mesta 1999). For F. p. anatum, known number of occupied eyries in 1997 was 301 in Alaska; 347 in Canada; 329 in Washington, Oregon, and California; 529 in the Rocky Mtns. and sw. U.S; and 205 hybrid- anatum from the Mississippi River to Atlantic Coast (Mesta 1999); additional 170 pairs estimated for Mexico and Baja California (Enderson et al. 1995a). Total estimated population, about 2,500–3,000 pairs (based on Enderson et al. 1995a and Mesta 1999). For F. p. tundrius, known number of occupied eyries was 104 in Greenland (estimated 400– 500 pairs, Falk and Møller 1988), 279 in arctic Canada (estimated at 1,500–2,000 pairs, G. S. Court, U. Banasch pers. comm.), and 158 in n. Alaska (estimated 400–500 pairs, T. Swem, B. Ritchie pers. comm.; compiled from Cade et al. 1988, Enderson et al. 1995a). Estimated total: 2,300–3,000 pairs. Estimates based on counts of migrants in 1980 suggested total boreal population (tundrius and northern anatum) ranged between 6,700 and 13,000 pairs (Cade et al. 1988); in autumn 2000, >2,000 migrants counted in Florida Keys (J. Larrabee, J. En-derson pers. comm.), and 4–5 migrants estimated at each of >4,000 offshore oil rigs in Gulf of Mexico during Oct (A. Wormington, fide Pendergrass 2000, R. W. Russell pers. comm.). For F. p. pealei, known number of occupied eyries in 1990s was 271 in Alaska, 77 in British Columbia, 17–20 in Washington, and about 5–10 in Oregon (Cade et al. 1988, Enderson et al. 1995a, Wilson et al. 2000, C. M. Anderson pers. comm., D. Fenske pers. comm.), although not clear that all nesters on Washington/Oregon coast are pealei; estimated total nesting pairs, 850–1,000. Total continental breeding population estimated at 8,000–10,000 pairs at end of twentieth cen-tury and still increasing. Small proportion of increase represents increased effort to locate nesting pairs and to count migrants during past 30 yr (see below). If there are 8,000 breeding pairs, total population at end of breeding season, including immatures and floaters, could well be in range of 40,000–50,000 individuals (see Population regulation, below). Density Generally wide-ranging but sparsely distributed. Limited first by distribution of suitable nest locations and further by territorial spacing of pairs (Hunt 1998), the latter influenced by food availability (Hunt 1988, Ratcliffe 1993). Spacing of nesting pairs highly variable by region, but in some areas, superabundant food (colonial nesting seabirds) and few ground predators associated with greatly reduced spatial requirements for nesting; further affected by territorial spacing of pairs (Hunt 1988, 1998). Yearly territory reoccupancy rates about 85–90% in many regions (Enderson et al. 1995a), but lower in some (e.g., Arctic, where annual variations in prey and weather modify yearly suitability of some territories; see Johnstone 1998). Under favorable conditions, local density can reach 1 pair/10–20 km2 or higher, but 1 pair/100 to >1,000 km2 more typical for North America, in contrast to higher densities often found in Europe (Ratcliffe 1993). Density often best expressed as pairs/linear distance apart rather than pairs/area occupied, because breeding dispersion tends to be either dendritic along rivers and tributaries, linear along coastlines, or perimetric around islands and lakes. Maximum known density reported from range of F. p. pealei on Langara I., where superabundance of colonial nesting alcids and numerous nest sites (cliffs) reduce spatial requirements: Locally in Cloak Bay (linear shoreline about 1.7 km and area of about 520 ha) in 1952–1958, 5–8 pairs nested (Beebe 1960); for entire 42-km perimeter of island, estimates of 20–35 pairs (Brooks 1926, Beebe 1960), but <10 pairs in recent decades (see beyond). High densities also in Aleutians: Amchitka I., mean of 18.6 pairs along 193 km of shoreline (1 pair/10.3 km); 7 other Aleutian islands ranged from 1 pair/4.8 km to 1 pair/13.0 km (White 1975). Elsewhere in range of pealei, densities vary from 1 pair/10.0 km to 1 pair/80.0 km of coastline (Ambrose et al. 1988). Relatively high densities also occur in arctic mainland regions. Fyfe (1969) considered 1 pair/52 km2 average for optimum nesting habitat in Canadian Arctic and 1 pair/259 km2 for areas of limited nesting habitat. Along 293 km of Colville River, AK, in 1990s, density varied between 1 pair/3.2 and 3.8 km (51–61 occupied eyries, data from T. Swem). At Rankin Inlet, Nunavut, northwest corner of Hudson Bay, in area of 450 km2, nesting pairs varied from 17 in 1981 to 28 in 1993 (1 pair/16.0–26.5 km2); distances between pairs 0.7 to 9.8 km (Court et al. 1988, Swem and Ambrose 1994). Density in other regions of Northwest Territories ranged from 1/97 km2 to 320 km2 in early 1980s (Bromley 1988). In 1985, Mattox and Seegar (1988) found 40 occupied cliffs (38 pairs) in about 2,500 km2 area of Søndre Strømfjord region, w. Greenland (1 site/63 km2); in s. Greenland, 10–13 pairs found in land area of 2,636 km2 between 1981 and 1985 (1 pair/203 to 264 km2; Falk and Møller 1988). In taiga zones: along 265 km of central Yukon River, AK, 25–46 pairs nested between 1988 and 1998 (1 pair/5.8–11.1 km), and along 375 km of Tanana River, AK, 12–33 pairs nested in same period (1 pair/11.4–31.3 km; Ambrose et al. 1988, Mesta 1999); along about 1,440 km of Mackenzie River, Northwest Territories, 85 pairs nested in 1990 (1 pair/18.1 km; Enderson et al. 1995a). Former densities in e. U.S.: (1) Delaware Valley of New Jersey, 39 known eyries in about 55,980 km2 but maximum of 21 occupied in 1940s (1 pair/about 2, 666 km2; Rice 1969); (2) in about 25,900 km2 around New York City prior to 1940s, 19 pairs (1 pair/1,363 km2; Hickey and Anderson 1969); (3) 28 known eyries in Vermont before 1940 (1 site/858 km2; Berger and Mueller 1969). Representative densities of known eyries in w. North America: (1) Pacific Coast of Baja California from Los Coronados Is. to Asuncion I., 42 known eyries prior to 1964 along about 960 km of coastline and offshore islands (including about 6 eyries on 10.4-km2 Natividad I. (Lamb 1927), 1 eyrie/approx. 23 km (Banks 1969, Porter et al. 1988). (2) Sierra Madre Oriental, Mexico, 6 pairs in circle with 25-km diameter, spaced 4.2–8.1 km apart (Hunt et al. 1988). (3) Green River, Dinosaur National Monument, CO/UT (12–15 pairs in 77 km2; S. Petersburg pers. comm.). (4) Colorado River, Grand Canyon National Park, AZ, 71 breeding areas in 1988–1989 between Lees Ferry and Lake Mead, a 444-km river and canyon corridor; in 1,158 km2, 1 breeding area/16.3 km2. (5) For California, Sierra Nevada region, 49 historical eyries in 146,335 km2 (about 1 site/3,000 km2); northern coast region, 49 eyries in 32,022 km2 (1 site/654 km2); San Francisco Bay region, 22 eyries in 10,360 km2 (1 site/471 km2), 17 occupied in 2001 (B. Walton pers. comm.); central coast region, 93 eyries in 34,965 km2 (1 site/376 km2); south coast region, 31 eyries in 30,433 km2 (1 site/982 km2; Thelander 1977); in 2001, Long Beach, CA, had urban/industrial population of 7 pairs in about 25 km2 area (pair/3.6 km2) with mean nearest neighbor distance of 1.85 km (range 1.2–2.94). (6) Columbia River Palisades, 13 known eyries (about 1 site/7.0 km; R. M. Bond in Nelson 1969). (7) Okanagan Lake and River, British Columbia, about 15 eyries, including Vaseux Lake with 3 pairs on 800-m cliff (1 site/9.7 km; data from A. Brooks in Nelson 1969). Trends (See also Conservation and management, below). Unstudied prior to 1930s–1940s (Hickey 1942, Bond 1946). Sparse, tree-nesting population in Mississippi River basin mostly gone by early 1900s owing to loss of big trees, 4 sites in cypress swamps of Ten-nessee and n. Louisiana remained occupied into 1940s (Hickey and Anderson 1969). Hickey (1942) estimated possible 10–18% decrease in occupancy of all known eyries (408) in e. North America by about 1940, but cautioned that permanent abandonment of nesting territories is difficult to determine (pair may move to undetected alternate sites); in Pennsylvania/New Jersey, 16 of 39 eyries abandoned prior to 1940 (Rice 1969), possibly owing to increased depredations of Great Horned Owl (TJC). In w. North America, 14 (4.3%) of 328 eyries abandoned before 1940 owing to human influences (Bond 1946); 80–90% of Peregrine eyries abandoned in intermountain region of n. Utah, w. Wyoming, w. Montana, Idaho, Oregon, and Washington (>50 known eyries deserted, many taken over by Prairie Falcons) from 1940 to early 1950s, perhaps related to period of low precipitation and consequent biotic changes between 1920 and 1960 (Nelson 1969). Otherwise, continentwide population before World War II considered stable, and breeders characterized by traditional use of same eyries and territories over periods measured in decades and centuries (Hickey 1942, Bond 1946). Prior to DDT use, number of territories estimated at 7,000–10,000 in North America (Kiff 1988), plus about 450 in Greenland (Falk and Møller 1988), with 10–15% of total territories unoccupied in any given year (actual occupancy rate higher because use of alternate sites sometimes undetected). Precipitous population crash in 1950s to mid-1970s owing to effects of DDT (DDE) on reproduction (thin eggshells and embryo fatalities, and possibly increased fatalities of adults from HEOD [dieldrin, aldrin] resi-dues in prey; Hickey 1969, Cade et al. 1988, Mesta 1999; see Conservation and management, below). Decline began in temperate parts of range and spread northward into arctic regions. By 1965–1970, breeding populations totally extirpated in U.S. and s. Canada east of Rocky Mtns. to Atlantic Coast and south of boreal forest, and greatly reduced (10–50% of pre-pesticides numbers) in different parts of western range; in northern regions, populations declined from about 1969 to about 1975 by 50–75% (or virtual extirpation locally; e.g., Tanana River, AK, north slope of Yukon Territory; Fyfe et al. 1976, Cade et al. 1988). F. p. pealei little affected by pesticides but local populations (e.g., Langara I., British Columbia) declined in same period in relation to dramatic reduction in seabird populations associated with major changes in marine ecosystem (Nelson and Myres 1976) and possibly increased rat predation (Nelson 1990). Population stability or increase locally noted by late 1970s (Fyfe et al. 1976, White et al. 1990). After restrictions on use of DDT in Canada in 1970 and in U.S. in 1972 (37 FR 13369) and HEOD compounds in 1974 (39 FR 37246), number of nesting pairs increased rapidly in 1980s (Cade et al. 1988). Aided by release of >6,000 young produced or reared in captivity in s. Canada and coterminous U.S. (Holdroyd and Banasch 1996, Cade 2000), by 1990s continentwide numbers approached pre-DDT level, although distribution of nesting pairs was different, with some former areas still depleted, others with higher density than historically known, and some formerly unused habitats (urban and industrialized areas and coastal salt marshes) occupied for first time (Enderson et al. 1995a, Cade et al. 1997, Mesta 1999). Increase in population continuing into twenty-first century (e.g., Tordoff and Redig 2001). top POPULATION REGULATION Healthy populations stable overall for several reasons related to interplay among natality, mortality, dispersal, and territoriality. Many floaters of both sexes, excluded by territory holders, buffer breeding segment by quick replacement of lost breeders (Ratcliffe 1993; see Johnstone 1998, for results of first removal experiment with Peregrines). Occurrence of floaters indicates that serviceable breeding locations and cohorts from them strictly limited, a constraint bounding populations in state of equilibrium (Hunt 1988, 1998). Number of pairs varies little annually because properties of the nesting situation are primarily physiographic, including those influencing prey availability and suitability of nest sites, and vacancies are immediately filled by floaters. Some populations may respond to climatic cycles influencing prey numbers over long term, and nest success may be reduced at arctic territories some years owing to bad weather and unpredictable prey numbers (Bradley et al. 1997); but these factors less influential in temperate and tropical regions. If vital rates are high, density feedback may adjust equilibrium population size through floater pressure, impacting breeder survival and possibly nest success (Monneret 1987, Haller 1996, Hunt 1998). Food competition among nonbreeders may not regulate their numbers because (1) “survival habitat” without cliffs is vast relative to breeding habitat and (2) extreme variety of potential prey dampens population-scale impact of Peregrine depredations. Populations far more sensitive to changes in adult survival than juvenile or subadult survival or reproduction. In hypothetical population producing 1.5 young/territorial pair, where annual adult survival = 0.83, subadults = 0.70, juveniles = 0.50, there would be 1 floater/breeding pair at equilibrium (Moffat’s equilibrium model; Hunt 1998). Reducing floaters to zero (i.e., placing population at decline threshold), requires 11% reduction in adult survival. Same result requires 33% reduction in either subadult or juvenile survival or reproduction. Although both natal and breeder dispersal are known (see Range, above), exact role of emigration and immigration not yet determined; usually assumed to cancel each other, but some populations may be sources, others sinks. Several models based on conventional calculations of growth rate (lambda) derived from Leslie matrix or life-table statistics have been applied to Peregrines (Grier and Barclay in Cade et al. 1988, Wootton and Bell 1992). Moffat’s equilibrium model (Hunt 1998) offers best framework for understanding natural regulation of falcon populations at environmental carrying capacity, because it is based on spatially imposed limits to productivity and calculation of floater-to- breeder ratios at equilibrium rather than growth rate. According to Moffat’s equilibrium model (Hunt 1998), populations with adult mortality of 30% can remain stable or produce slight surplus of floaters only when juvenile mortality is <50%, unrealistically low, and productivity is 2.0 young/pair. Thus, some estimates of adult mortality for highly migratory, arctic populations must be too high, since they are known to have numerous floaters and have generally increased by factor of 2–4 in last 25 yr. Similarly, 37% female mortality on Langara I., British Columbia, with productivity of 2.31 young/pair would require juvenile mortality to be no more than 49% just to maintain breeder stability with no surplus floaters. Since floaters are reported to be common, estimates of adult mortality based on uncorrected turnover must be too high, owing either to breeder dispersal or misidentification of individual falcons. The classic, stable Peregrine population is basically resident, with annual adult mortality ranging from 10 to 15% and productivity of 1.0–2.0 young/ pair, maintaining significant numbers of floaters at all com-binations of juvenile mortality and productivity except when juvenile mortality reaches 70% and productivity is 1.0 young/pair. Breeding population is highly buffered by floater-to-breeder ratios commonly in range of 1:1 to 2:1.

CONSERVATION AND MANAGEMENT EFFECTS OF HUMAN ACTIVITY | MANAGEMENT

EFFECTS OF HUMAN ACTIVITY Disturbance at eyries Much as described for Prairie Falcon (Steenhof 1998). Pairs vary greatly in responsiveness to human activities, depending partly on individual characteristics, partly on period of breeding cycle, and partly on environmental circumstances (Cade 1960). Pairs in remote locations most reactive; those in urban areas or frequently visited sites become habituated to close human activities. In past, some historical eyries were abandoned because of human encroachments or increased levels of nearby activity (Hickey 1942, 1969; Bond 1946), but not a major factor in population change. Also, temporarily abandoned eyries sometimes reoccupied after disturbance ceased (Bond 1946, Herbert and Herbert 1965), in some cases after many decades (Ratcliffe 1993). Rock-climbing and activity of researchers at eyries not usually detrimental when reasonable precautions taken (Olsen and Olsen 1978, Cade et al. 1996; see working bib-liography of Porter et al. 1987, for >80 references to effects of disturbances). Shooting, trapping, and egg-collecting Before legal protection, these activities accounted for loss of many hundreds of falcons and their eggs. Often shot at famous migration passes (e.g., Fisher’s I., NY; Hawk Mountain, PA; Cape May, NJ; Whitefish Point, MI); however, systematic persecution as practiced by European gamekeepers was rare, occasionally done by pigeon fanciers (Bent 1938). Nonetheless, rein-troduced urban population in greater Los Angeles, CA, area in 1990s received considerable pressure from pigeon fanciers with 14 shot, adults and young, at 1 territory over 4 yr, but with no loss of eyrie occupancy (B. Walton pers. comm.). Small numbers of nestlings/fledglings and first-year migrants also taken by falconers in period 1920s through 1960s before protection under Endangered Species Act in 1970 and Migratory Bird Treaty Act in 1972, and afterward, in case of F. p. pealei. No evidence that losses from these activities depressed number of occupied nesting territories, except in isolated, local circumstances. Reputed cases of impact from taking nestlings include: (1) lower Hudson River, NY (Herbert and Herbert 1965); (2) 40-km stretch of river in Alberta (Dekker 1967); and (3) Langara I., British Columbia (Dekker 1969, 1972), but overriding effects of pesticides and/or reduced food supply were operative in these places at same time. Pesticides and other contaminants/toxins From late 1940s to early 1970s, massive, continentwide—indeed, nearly global—use of organochlorine pesticides, particularly DDT and HEOD (dieldrin, aldrin) in agriculture and forestry and for human disease control resulted in bioaccumulation of toxic residues in prey species, which in turn contaminated falcons, causing both lethal and sublethal effects (see review papers in Cade et al. 1988). Few fatalities documented in North America (Reichel et al. 1974, Peakall et al. 1990), but HEOD considered important cause of death among British Peregrines in 1950s–1960s and in some other parts of Europe (Ratcliffe 1993); circumstantially implicated as lethal factor in North America (Nisbet 1988). Most significant sublethal effect of DDE (persistent environmental residue of DDT) was repro-ductive malfunction resulting from abnormally thin eggshells. First identified in Great Britain (Ratcliffe 1967), this thin-eggshell syndrome was quickly confirmed as widespread condition of North American Peregrines, coincident with North American use of DDT beginning in late 1940s (Hickey and Anderson 1968; Cade et al. 1971, 1988; Court et al. 1990; Johnstone et al. 1996). Direct correlation exists between concentration of DDE residues in egg contents (reflects circulating levels in laying female) and eggshell thickness, r- values ranging from - 0.57 to -0.75 in different geographic samples (Cade et al. 1971, Peakall and Kiff 1988, Newton et al. 1989, Court et al. 1990). Peregrine population declines in 1950s–1970s associated with population averages for eggshell-thinning of >18% and residue levels of 15–20 ppm wet weight DDE in egg contents (Hickey and Anderson 1968, Peakall et al. 1975), and with associated reduction in breeding success (reviewed by Fyfe et al. 1988). In arctic Canada from 1981 to 1985, eggs from failed nests had shells averaging 20.2% thinner than normal, while eggs from successful nests averaged 16.1% thinner (Court et al. 1990). Affected populations showing these thinning correlations in North America include e. U.S. (New Jersey, Massachusetts), n. Alaska, interior Alaska, Ungava, n. Quebec, Colorado and Rocky Mtns., and California, as well as others world-wide (Peakall and Kiff 1988). Subsequent population recovery in all these regions following 1980s associated with reduced pesticide residues in prey and in eggs and body tissues of Peregrines, increased eggshell thickness, and increased productivity (Cade et al. 1988, Peakall et al. 1990, Enderson et al. 1995a, Mesta 1999). PCBs, mercury, and lead are other environmental contaminants often implicated in bird morbidities and fatalities, but none known to have exerted population effects on Peregrines in North America (DeMent et al. 1986, Stone and Okoniewski 1988, Peakall et al. 1990). Peregrines occasionally killed by eating birds poisoned by strychnine or other persistent toxic chemicals (see Porter et al. 1987 for specific references). Collisions with stationary/moving structures or objects Urban-dwelling Peregrines killed or injured by flying into windows or other features of buildings while chasing prey, occasionally by collision with moving vehicles, including aircraft at airports; sometimes strike wires; recently fledged young sometimes fall down chimneys or are killed by air-conditioning equipment or other machinery on tops of buildings; young in nests on bridges often fall into water, significantly reducing productivity at such sites (Barclay and Cade 1983, Cade and Bird 1990, Frank 1994, Bell et al. 1996). In California, electrocutions and wire strikes common in nonurban areas, as well (B. Walton pers. comm.). For other accidental injuries and fatal-ities, see Porter et al. 1987. Degradation of habitat Difficult to assess impact on Peregrine because species is so catholic in use of wide range of habitats and landscapes, including those highly modified by humans. Most affected by loss or modification of nesting places, which are limited in number and often nonreplaceable (e.g., cliffs, ledges, special trees, towers, buildings; see Steenhof 1998 for parallel with Prairie Falcon), but has latitude to switch among alternate nesting places in same territory where >1 exists (e.g., from building to stone quarry in Salt Lake City, UT). Unlike Prairie Falcon (Steenhof 1998), agricultural practices not usually detrimental to Peregrine, except use of pesticides, as species readily preys on birds attracted to cultivated landscapes, and owing to hunting style no doubt benefited from conversion of closed-canopy forests to agriculture, as occurred in ne. U.S. in 1700s and 1800s. Migratory and wintering Peregrines, and some breeders, favor wetland areas that support concentrations of waterfowl and shorebirds; loss or degradation of these habitats is no doubt detrimental to the species. Systemic changes in ecosystem functions (e.g., impact of warmer water temperature on marine food web and consequent reduction in plankton and associated seabirds that serve as food for Peregrines in Queen Charlotte Is.; Nelson and Myres 1976) can exert major impact on Peregrine populations (see J. Thiollay 1988 and Ratcliffe 1993 for other examples). Deleterious impacts of research Careless methods of field study can result in injury or death of adults and young, or abandonment of eggs (no known case of abandoning young), but such impacts not known to have measurable effect on long-term population stability. Inspection of nest site just before or during laying likely to cause falcons to abandon that site and renest elsewhere on same cliff or in same territory. Sudden appearance of human, or helicopter, near nest can frighten sitting bird to leave so quickly that eggs or recently hatched young may be kicked out of the nest (Cade 1960). Prolonged investigations that keep parents off eggs or downy young for varying periods, depending on climate and age of young, can cause overchilling or overheating and death. Attempts to band young >4–5 wk old can result in premature departure from nest, increasing their vulnerability to predators (Cade et al. 1996). Trapping adults or flying juveniles sometimes results in injuries; placing identification markers or telemetry transmitters on falcons can reduce survivability. Need for information derived from disturbing procedures must be balanced against risks of injury or fatality resulting from study methods. Fyfe and Olendorff (1976) and Olsen and Olsen (1978) provide guidelines for minimizing impacts of human disturbance at eyries (see also Cade et al. 1996). top MANAGEMENT Legal protection No legal protection in North America prior to 1930s. First protected by state law in Massachusetts, New York, and New Jersey in 1934 (Herbert and Herbert 1965, Hagar 1969); most states and Canadian provinces/territories protected Peregrine from unauthorized take by 1950s–1960s. F. p. tundrius and F. p. anatum officially listed as Endangered in 1970 in U.S. under 1969 Endangered Species Conservation Act (Public Law 91-135, 835 Stat. 275) and later transferred to 1973 Endangered Species Act (16 U.S.C. 1531 et seq.); protected with other birds of prey under Migratory Bird Treaty Act (16 U.S.C. 703-712) through agreement with Mexico, but not Canada, in 1972. Also protected from unregulated international trade by inclusion on Appendix I of Convention on International Trade in Endangered Species of Wild Fauna and Flora in 1975. Management as Endangered species Efforts to propagate and release falcons began in late 1960s (Cade et al. 1988, Enderson et al. 1995a) and involved primarily actions by The Peregrine Fund, Inc., Cana-dian Wildlife Service, and several private ventures, followed later by Santa Cruz Predatory Bird Research Group (Univ. of California, Santa Cruz) and the Raptor Center, University of Minnesota. Under the Endan-gered Species Act of 1973, 4 regional-recovery plans were developed for (1) Alaska; (2) California, Oregon, Washington, and Nevada; (3) Rocky Mountain and southwest states; and (4) e. U.S.; Canada also produced nonstatutory plan in 1988 (see Mesta 1999 for sum- maries). These plans established methods and criteria for recovery; all but Alaska plan relied heavily on captive propagation and release of captive-produced birds. All plans emphasized need for reduction in environmental contamination by organochlorine pesticide residues, especially DDT. Experimental releases of captive-produced falcons by hacking and fostering began in U.S. in 1974 and 1975 (Barclay and Cade 1983) and by fostering in Canada in 1975 (Fyfe 1988). By 1998, nearly 7,000 Peregrines had been released in North America (L. F. Kiff unpubl.), resulting in minimum of 700 re-established breeding territories (pairs in s. Canada, e. and midwestern U.S., Rocky Mtns., and Pacific Coast; TJC based on data in Mesta 1999). Also, as a result of de-creasing organochlorine residues in the environment and strict protection of surviving remnant populations, wild Peregrines began increasing in the late 1970s, first in arctic and boreal regions, but also in Southwest and Baja California and other western locations. Most of this increase resulted from residual pairs that survived the worst effects of organochlorine contamination (Enderson et al. 1995a, Mesta 1999). By 1998 known number of occupied and successful territories in North America indicated practically complete recovery and a demographically viable, continental population (see Demography and populations: population status, above, for details). Annual federal and state costs for recovery of anatum placed at >$5.4 million in the 1990s (Restani and Marzluff 2001), but partly used for law enforcement, habitat improvements, and other peripheral activities. F. p. tundrius down-listed to Threatened in 1984 (49 FR 10520) and delisted 1994 (59 FR 50796) F. p. anatum delisted 1999 (Vol. 64, no. 164: FR 46542–46558). ESA amendment (section 49 (g) (11)) requires minimum 5-yr post-delisting monitoring in cooper-ation with state agencies to make certain delisted species maintain nonthreatened status. For F. p. tundrius, monitoring focused on breeding populations in following regions: Colville River, AK, and Hope Bay, Coppermine, and Rankin Inlet, Nunavut; also, on number of migrants counted at Assateague I., VA, and Cape May, NJ, and Padre I., TX (Swem and Ambrose 1994). No official report issued, but it is known that these populations either increased or remained stable through 1999. For F. p. anatum, more elaborate system of monitoring developed by ad-hoc committee involves random sampling to detect whether decline in number of breeders occurs over 10-yr period (63 FR 45460). Management needs and objectives for future Long-term, continuing objectives under Migratory Bird Treaty Act, state, and Canadian provincial/territorial jurisdictions include: (1) habitat protection, (2) habitat improvements/manipulations, (3) monitoring population trends and productivity, and (4) sustained yield use for falconry. Most important components of habitat requiring special attention are traditional nesting places (eyries), which should be protected from physical alteration or destruction and from excessive human disturbances that might cause abandonment or repeated reproductive failure; also, both coastal and inland wetlands that support abundance of prey species needed, particularly by migrating and wintering falcons, especially barrier islands and associated lagoons. Habitat improvements/manipulations include modifications of nest sites on cliffs, buildings, towers to increase safety from predators and inclement weather; construc-tion of improved, alternate nesting places, including towers or other structures, for safe placement of nest sites. General-habitat improvements that increase the abundance of bird life also beneficial for Peregrines. Detailed guidelines for managing Peregrines include: survey and sampling techniques, banding, observing behavior, collecting tissue samples, aging young, management of specific types of eyries, and manipulations of eggs and young to increase distribution and abun-dance (Cade et al. 1996). Once nesting populations stabilize at carrying capacity, little active management should be needed, as Peregrine historically survived for centuries in face of both natural and human- caused losses. Existence of sizable, adult floater surplus (see Demography and populations: population regulation, above) buffers breeding population from annual variations in mortality; also represents potential for further increasing size of breeding population by provision of additional suitable nesting places (e.g., towers; nest sites on buildings, bridges, smokestacks, natural cliffs), and by natural expansion of range into previously un-inhabited regions (e.g., Cuba). This potential far sur-passes the requirements for a secure and viable North American population. Management of hybridization Breeding with Prairie Falcon in Utah and Canada (Oliphant 1991; both involved Prairie Falcons previously in captivity). Young removed from Canadian nest 3 seasons (ration-ale was to prevent genetic introgression of natural gene pools). Utah mating of male Peregrine and female Prairie Falcon in 1986 produced 4 young; given to falconers; then adult female trapped and relocated. Male Peregrine bred with hybrid Peregrine × Gyrfalcon in Colorado (1996), and 2 infertile eggs were in eyrie; hybrid trapped (J. H. Enderson pers. comm.). Male Peregrine × Prairie Falcon escapee produced young with female Peregrine at nest on church in Washington, D.C., for 5 seasons; young removed and male finally caught and removed (C. Koppie pers. comm.). Hybridization probably not significant because of low hybrid × hybrid fertility.

APPEARANCE MOLTS AND PLUMAGES | BARE PARTS

MOLTS AND PLUMAGES

Peregrine Falcom juvenile on a Swallow box; Jamaica Bay WR, Queens, NY; Feb.

Peregrine Falcon standing on its prey, a pigeon; Jones Beach St. Pk., LI, NY; Feb. Description of F. peregrinus anatum modified, in part, from Friedmann 1950, C. White in Palmer 1988, Clum et al. 1996. Also based on examination of over 2,000 museum specimens by authors and several thousand Peregrines in captivity. For descriptions of other subspecies, see Systematics, above. Hatchlings At hatch, weight about 35–40 g, covered with off-whitish first down. Mass doubles by day 6, and very white second down starts to emerge, first on humeral and alar tracts and dorsal surface of wings. Following description differs slightly from Palmer (1988), who follows Witherby et al. (1943). First down, present at hatching (down A of Witherby et al. 1943) consists of prepennae, and later remains attached to tips of emerging Juvenal contour feathers. Second down consists of 2 types: (1) scattered preplumulae that emerge attached to tips of plumulae (down B of Witherby et al. 1943) and (2) plumulae that emerge directly from their follicles (down C of Witherby et al. 1943). Most of second down consists of latter kind. Time of emergence, abundance, and distribution of B-down needs study. Juvenal plumage By day 10, unsplit sheath of remiges and rectrices several millimeters long. By day 14, second down very dense and covers base of feather sheaths, although rectrices starting to emerge from sheaths. At day 20, contour feathers visible from beneath heavy white second down normally only at margins of wings, tail, faintly around eyes, and base of lower mandible. By day 30, appears about half down, half feathers. Mostly feathered but retains large patches of down around legs, wings and on top of head at day 35. Almost fully feathered with traces of down on top of head and under wings; remiges 10–6 and rectrices 6–4 not fully grown, but bird capable of weak flight. Full Juvenal plumage is geographically variable but well described. For F. p. anatum, head, crown, and nape variable but usually some shade of sepia or fuscous; feathers may have large amounts of buff edgings so head appears lighter than dorsum; buff ocelli markings may cover most of nape or may be obscured by dark edgings on nape-feathers. Forehead usually pale buffy, and color may extend back over crown so that center of crown is lighter than sides of crown. Frequently pale streak through eye. Dark “malar” or “moustache” stripe variable, usually narrower than in Definitive Basic; stripe may be broad and join a completely dark auricular region or be narrow and set off by pale-buffy auricular region. Narrowest stripes may be interrupted at base by pale-buffy streak, similar to tundrius. Entire upperparts some shade of sepia to fuscous; feathers with pale buff to tawny margins; rump may appear paler because pale buffy-rufous margins are wider. Margins often wear off and dorsum appears solid color. Upper wing-coverts as in back but may lack light edgings; primaries dark brownish where black in Basic; inner web of each primary with up to 10 pale-buffy spots or bars (in palest) distributed along length of feather, secondaries with similar, but less well-defined spots or bars. Background color of underparts tawny to pale buff, with chin typically more whitish. Underparts streaked with some shade of fuscous (sepia) similar to dorsum; streaking may take shape of arrowhead or teardrop. Feathers on thighs may have larger portion sepia than buff, giving appearance of bars and thus darker than remainder of underparts or streaking may be finer than remainder of underparts. Upper surface of rectrices quite similar to back in color but with 5–7 pale rufous, often bluish, patches in form of bars or large spots, but may be solid without markings, especially central pair of rectrices; 5–10 mm buffy tip fading to whitish. Pale tip may disappear when feathers heavily worn. Sexes alike, but females average darker. Dark, but typical, immature anatum from Ohio erroneously allocated to pealei based on plumage saturation (White 1972). Definitive Basic plumage Acquired in second year of life. Definitive Prebasic molt generally complete, but when Juvenal feathers retained (no true Basic I plumage because retention of Juvenal feathers individually variable), they are usually primary or secondary wing-coverts or rump-feathers; otherwise scattered Juvenal contour feathers can also be found. First assumption of Definitive Basic may be darker than subsequent plumages but not definable and individually variable (see Palmer 1988). Resident may begin molt in Apr but arctic migrant female, a week or so before male, usually starts mid- to late Jun. Northern female interrupts molt during brood-rearing. Rectrices usually later than remiges. Primary (P) molt sequence, normally inward and outward from P4 so usually P4, 5, 3, 6, 7, 2, 8, 1, 9, 10. Secondary (S) molt mostly in-ward and outward from S5, so usually S5, 7, 4, 8, 3, 6, 9, 2, 10, 11, 1. Tail (R) starting with central pair usually outward so R1, 2, 3, 6, 4, 5. Midlatitude-temperate birds usually 4.5–5 mo and finished by Sep, but neo-tropical migrants frequently have R4 and R5 partly grown in Oct and may complete P10 in Jan, 8 mo after starting molt. Some resident juveniles in California (n = 8 banded birds) molt body, head, back, and part of breast in first winter (B. Walton pers. comm.); also noted in e. U.S. and in some migrating tundrius juveniles (TJC). Male. F. p. anatum. Upperparts variably dark bluish gray, toward slaty, with paler middle and lower back and rump, somewhat obscure darker bars not evident on head and shoulders, becoming more evident on lower back, rump and upper tail-coverts. Small (3–5 mm) whitish forehead band often present, usually larger or move evident in lighter birds; malars slightly darker than head and may cover more than two-thirds of side of head with small pale area on auricular region or, if malar is more narrow, pale auricular usually not closer to eye than about 12–15 mm. Underparts with chin to crop and upper breast unmarked and white to whitish buff, remainder varies from whitish buff to rich tawny buff often with grizzle or grayish overwash most evident on flanks and thighs. Grayish-black markings varying from shaft- streaks on upper breast to spots or thin transverse bars lower down; bars may approach chevrons and heaviest on flanks and thighs. Upper wing-coverts and tertials color of back with darker bars. Upper surface of remiges same color as back, except primaries appear darker (more blackish). Inner web of primaries with 10–14 pale bars; secondaries with darker bars throughout. Under wing-coverts whitish grayish narrowly barred with black. Upper surface of tail with bluish basal half and darker-blackish distal half tipped with white and crossed with up to 10–12 dark transverse bars, wider progressing toward tip. Bars on cen-tral rectrices sometimes not evident when faded. Under tail-coverts variable—whitish/grayish/buffy— crossed with black bars. Female. Similar to male but underparts on average more buffy and heavily marked with larger markings extending farther up on breast and into crop; upperparts browner. Whitish basal portions of nape-feathers more extensive, giving nape and ocelli slightly mottled appearance more frequently. top BARE PARTS Bill At hatching, typically pale blue-gray with white egg tooth, which is lost within few days; in unfledged juvenile, blue-gray, darker at tip. By fledg-ing, color approximates adult’s. Adult bill muted slate blue, tinged yellowish at base and black at tip. Facial skin At hatching, pale-bluish cere and lore. Immature variable by geography and/or within clutch; at fledging, deep- to pale-yellowish to greenish to bluish. Adult variable yellow toward orange. Male usually brighter than female, both brighter in breeding season. Iris Dark brown at all ages. Legs and feet At hatching, gray-white to grayish. Immature variable, apparently not related to sex, geography, or within brood so appears to be both genetically controlled and also function of food; in captivity, diet of egg yolks (carotenoids) causes deeper yellow color. At fledging, most western anatum frequently yellowish, with some nearly as bright as adult. Former eastern anatum bluish gray to bluish green, infrequently yellow (W. R. Spofford pers. comm.). Adults vary from yellow toward orange. Males of all races tend to be brighter and deeper yellow in breeding season. Talons pale at hatching and then black in all other ages. A sample of 90 Peregrines had distinctive toe-scale patterns on middle toe that allowed for individual identification (Smith et al. 1993).

MEASUREMENTS LINEAR | MASS Size variation complex but generally decreases, somewhat clinally, northwest to southwest in w. North America and east to west in temperate latitudes; decreases slightly west to east in tundra (see White 1987). Current pattern in e. U.S. complicated by in-troduction in 1970s– 1980s of mixtures of 7 subspecies of varying size and appearance: nominate peregrinus (from Scotland), tundrius (Alaska and Canada), anatum (w. U.S. and Canada), brookei (Spain), cassini (Argentina), pealei (both Queen Charlotte and Aleutian Is. subgroups), and macropus (se. Australia; Barclay and Cade 1983, White and Boyce 1988, Tordoff and Redig 2001). top LINEAR Standard linear measurements given in Appendix 2). Female larger than male in all dimensions (said to be one-third larger), no overlap in adult wing or tail measurements; female tails 16–18% longer, wings 12–14% longer, tarsi 10–11% longer. Measurements do not reflect those of the current populations breeding in the e. U.S. and parts of Midwest, where the 3 North American and 4 exotic gene pools were introduced and presumably all interbreed. Sizes that will eventually result in that region must await determination until after selection has come to some stabilization. This will depend on degree of crossing between individuals of different taxa and on fitness of resulting intergrades. Measurements of 2 of the exotic taxa shown in Appendix 2. Each subspecies has defined subgroups that show some differences. Across range of tundrius, adults in Greenland (n = 46) have mean wing length (and tails) in male, slightly longer (not statistically significant) than remainder of tundra birds (n = 90). Along west coast, pealei from Aleutians (n = 64) have slightly shorter wings but longer tails (not statistically significant) than those of se. Alaska and Canada (n = 80). top MASS Body mass varies considerably by geographic origin, age, and throughout year—also with amount of food in stomach/crop (difficult to determine), which may exceed 100 g. Largest, pealei, breeding-season male averages about 894 g (740–1,058), female averages 1,201 g (1,005–1,595; Beebe 1960, museum specimens). Yukon River taiga anatum breeding-season male mean 652 g ± 52.38 SD (590–810, n = 23), female 977 g ± 76.35 SD (760–1,194 [n = 82]; R. Ambrose pers. comm.). Nunavat tundrius, breeding-season male mean 607 g ± 42.42 SD, female mean 920 g ± 55.28 SD (Court et al. 1988). Greenland tundrius breeding-season male mean 598 g (528–650, n = 23), female 959 g (797–1,130 [n = 87]; 797 g was outlier, next lightest 832 g [n = 3]); mass included crop contents; some individuals weighed in repeated years varied as much as 100 g (data from W. G. Mattox unpubl.). Most data from migrants are birds of undetermined origin and first-year birds may be somewhat thin, perhaps food-related. From migrants on Texas Gulf Coast, first-year female mean 942 g (810–1,090, n = 12), male 613 g (560–725, n = 5); second-year female mean 1,029 g (810–1,250, n = 36), male 641 g (600–675, n = 3), adult female mean 976 g (780–1,155, n = 51), male 612 g (530–665, n = 4; data from T. L. Maechtle, W. G. Mattox unpubl.). top

PRIORITIES FOR FUTURE RESEARCH Priorities include: (1) Document changes in morphological variation that may occur from nonassortative mating of progeny of the mixed population of 7 different subspecies released in e. North America during reintroduction. (2) Continue to monitor Peregrine distribution and abundance as reintroduced or recovering populations increase, to help determine carrying capacity now, as environments have changed in several decades since the population decline (see also Abbitt and Scott 2001). (3) Study frequency of breeder dispersal in different regional populations and its influence on estimates of adult survival and on population dynamics. Further study of natal dispersal would be useful; are some populations sources and others sinks? As telemetry techniques are refined, use of these to provide more extensive data on wintering locations of given breeding populations is important. (4) Perform more removal experiments to determine whether male and female replacements differ between poor- and high-quality territories (see Johnstone 1998). (5) Assess changes in reproduction, age of first breeding, and survival of prebreeders and breeders in relation to increased population density and saturation of nesting habitat. See Conservation and management, above, for future concerns, and Cade et al. 1996 and Pagel et al. 1996 for other recommendations and concerns.

ACKNOWLEDGMENTS North American specimens examined in University of Alaska Museum; American Museum of Natural History; University of Amsterdam Zoologish Museum; Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” in Buenos Aires, Argentina; Berlin Museum; British Museum (Natural History); University of British Columbia; California Academy of Sciences; University of California at Los Angeles; Canadian National Museum; Carnegie Museum; Chicago Museum of Natural History; University of Cincinnati; Cleveland Museum; Colorado Cooperative Wildlife Unit; Museum of Comparative Zoology;, University of Copenhagen Zoologish Museum; Cornell University; Denver Museum of Natural History; Ira Gabrielson collection in Patuxent Wildlife Research Center; Iowa State Museum; Museo de Historia Natural “Javier Pardo” in Peru; Kansas State Historical Society; University of Kansas; Los Angeles County Museum; Louisiana State University; Heinz Meng collection; University of Michigan; Milwaukee Public Museum; Montevideo; University of Minnesota; University of Nebraska State Museum; University of New Mexico Museum; New York State Museum; Occidental College; Ohio State University; David F. Parmalee collection; Peabody Museum; Academy of Natural Sciences of Philadelphia; Provincial Museum of British Columbia; Redpath Museum; Rijksmuseum Natural History in Leiden, Netherlands; Royal Ontario Museum; San Bernardino Museum, the Wilson Hanna Collection; San Diego Museum of Natural History; George M. Sutton collection; U.S. National Museum; University of Utah Museum of Natural History; Museum of Vertebrate Zoology; Burke Museum at University of Washington; Western Foundation of Vertebrate Zoology; University of Wisconsin. Numerous people contributed data (or reviewed parts of manuscript) particularly on distribution from: M. Amaral, R. E. Ambrose, C. M. Anderson, U. Banasch, M. Britten, R. W. Campbell, J. Castrale, G. Chilton, G. A. Court, J. H. Enderson, D. Fenske, G. Holroyd, L. F. Kiff, C. Koppie, T. C. Maechtle, W. G. Mattox, M. W. Nelson, R. W. Nelson, J. R. Parrish, J. Pagel, R. J. Ritchie, P. F. Schempf, T. Swem, H. B. Tordoff, D. Varland, and B. Walton.

ABOUT THE AUTHORS Clayton M. White received a B.A. and a Ph.D. in zoology from the University of Utah and did graduate work at University of Alaska. He is Professor of Zoology at Brigham Young University. He worked as a vertebrate ecologist for the U.S. Energy Research and Development Administration on issues dealing largely with arctic oil development. Research includes ecophysiology of finches and ecology and natural history of raptors, primarily falcons. He has served on 2 U.S. Fish and Wildlife Service recovery teams for the Peregrine Falcon. Current address: Department of Zoology, Brigham Young University, Provo, UT 84602. E-mail: [email protected]. Nancy J. Clum graduated from St. Lawrence University and received M.S. and Ph.D. degrees from Cornell University. Currently she is Assistant Professor of Environmental Science and Biology at DePaul University in Chicago. Her general research interests are in conservation biology and physiological ecology. Her current research concentrates on physiology and population biology of migrating Peregrine Falcons, patterns of growth and development in birds, and habitat structure and use in restored environments. Current address: Environmental Science, DePaul University, 2325 N. Clifton Ave., Chicago, IL 60614. E-mail: [email protected]. Tom J. Cade received a B.S. from the University of Alaska and M.S. and Ph.D. from the University of California, Los Angeles. He is currently Professor Emeritus of Cornell University and Founding Chairman of The Peregrine Fund, Inc. His studies have ranged from natural history and conservation to physiology in a variety of vertebrates, although his lifelong interest has been birds of prey. He is widely published on those disciplines and is author of The Falcons of the World. In addition to field studies in Africa, Arabia, Central America, Mauritius, Alaska, and the contiguous United States, he is involved in breeding falcons in captivity for release to the wild as a means of preserving rare or endangered species. This work has resulted in successful reintroductions of Peregrine Falcons in the United States and Mauritius Kestrels in Mauritius. Current address: The Peregrine Fund, 566 West Flying Hawk Lane, Boise, ID 83709. E-mail: [email protected]. W. Grainger Hunt studied Peregrine Falcon migration in coastal Texas for his 1966 master’s thesis and received a Ph.D. in zoology from the University of Texas at Austin in 1970, with a specialty in evolutionary genetics. He has studied the ecology of nesting Peregrines in Texas, Mexico, and the California Channel Islands. A commercial pilot, he has tracked Peregrines and Bald Eagles on long-distance migrations and has focused on aerial surveys of habitat selection and survival. He recently completed a 7-year investigation of Golden Eagle ecology, with emphasis on population dynamics modeling. Current address: The Peregrine Fund, 552-205 James Dr., McArthur, CA 96056. E-mail: [email protected].

OTHER NAMES French: Faucon pèlerin Spanish: Halcón peregrino

RECOMMENDED CITATION White, C. M., N. J. Clum, T. J. Cade, and W. G. Hunt. (2002). Peregrine Falcon (Falco peregrinus). The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Laboratory of Ornithology; Retrieved from The Birds of North American Online database: http://bna.birds.cornell.edu/BNA/account/Peregrine_Falcon/. doi:10.2173/bna.660

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