Migration

Nature Of Migration In The Species

Birds breeding above 70°N in Greenland are migratory (Salomonsen 1950); degree of migration above 70°N in North America unknown. Below 70°N largely resident, but some partial migration (Cade 1960, Platt 1977, Kuyt 1980, Norment 1985), probably mostly of immature birds and some adult females. Birds remaining on territory during winter are almost exclusively adults and predominately males (Platt 1977, Poole and Bromley 1988b, Nielsen and Cade 1990b). Birds wintering outside breeding range are mostly immatures and subadults (Nielsen and Cade 1990b, Sanchez 1993). Winter sightings suggest possible female bias in migrating birds (Platt 1976, Sanchez 1993). Immatures may move farther than adults; Nielsen and Cade (1990b) found a greater proportion of juvenile birds in southern than in northern Iceland, and Sanchez (1993) found that subadults remained in fixed area whereas immatures wandered generally south through study area.

Timing And Routes Of Migration

Movement out of breeding area begins late Aug and Sep (Salomonsen 1950, Salter et al. 1980, Nielsen and Cade 1990b, Schmutz et al. 1991, McIntyre 1994, Britten et al. 1995). Earliest records on wintering grounds Sep, more typically Oct–Nov; last sightings Jan–Mar, rarely to May in s. Canada and n. U.S. (Salomonsen 1950, Platt 1976, Wisely and Pinel 1987, Palmer 1988, Nielsen and Cade 1990b, Sanchez 1993, Flann 1998). In Yukon, unpaired birds first observed on nesting territories in Jan, evidence of occupation in Dec (Platt 1976, 1977). In coastal Northwest Territories (NWT), unpaired birds first observed in Mar–Apr, evidence of occupation in Feb (Poole and Bromley 1988b). In Greenland, breeding birds arrive in Apr (Salomonsen 1950). No known age-class bias in timing of movements.

In Greenland, migration primarily along seacoasts to s. Greenland and Iceland (Salomonsen 1950). Large numbers of migrating Gyrfalcons seen historically near Scoresbysund; many recently trapped there on migration (The Peregrine Fund 2005a). Recent satellite telemetry research by The Peregrine Fund should elucidate migration patterns in Greenland. In e. Canada, migratory movement along east coast of Labrador, Gulf of St. Lawrence, both coasts of Hudson Bay, and interior of Labrador Peninsula (Todd 1963). Movements in central and w. Canada known from small number of banded birds; movements typically, but not exclusively, southward (Poole and Bromley 1988b, Schmutz et al. 1991, Sanchez 1993). Of 5 recoveries of banded nestlings, 3 traveled south from nw. Canada, 1 traveled west from central Canada, and 1 traveled southeast from e. NWT to Ontario (Kuyt 1980, Schmutz et al. 1991). Five first-year birds banded in Canada moved 900–2,400 km during winter (Kuyt 1980, Schmutz et al. 1991). One nestling banded in NWT moved 145 km northeast but was probably recently independent (Poole and Bromley 1988b).

In Alaska, some movement of birds along Kenai Peninsula and Cold Bay. Four juvenile Gyrfalcons with satellite transmitters moved from Alaska into e. Russia within 4 weeks of fledging; three returned and wintered in Alaska (Britten et al. 1995). The remaining bird wintered near the Shantar Islands in the Sea of Okhotsk, having traveled more than 3,500 km. No directional trend in movements from the 9 transmittered juveniles though tended to use coastal and riparian areas (Britten et al. 1995). Some used the coastal areas of the Yukon and Kuskokwim Deltas in w. Alaska, as did at least 7 juveniles harnessed with transmitters and fledged from nests on the Yukon Delta National Wildlife Refuge (YDNWR). Two breeding adult females harnessed with transmitters on the YDNWR remained on or near their breeding site into the following winter (TLB, unpub. data).

At U.S. hawk watch locations, 2 records for Cape May, NJ (20 yr), and about 1 sighting/10 yr at Hawk Mountain, PA (S. Hoffman, P. Dunn, K. Bildstein pers. comm). Two Gyrfalcons captured at Kittatinny Mountain Research Station in New Jersey, one in fall of 2000 and 1982, both immature females (McDonnell 2001). Of 13 Hawk Watch International Migration sites and partners from 1999-2005, two Gyrfalcons observed (1999 and 2006, Bridger Mountain) and one at former site at Rogers Pass, MT in 1998 (J. Smith pers. comm., Hawk Watch International 2007). Between 1993-2005, 45 Gyrfalcons observed during fall migration and from 1993-2007, 24 observed during spring migration at Mt. Lorette, Alberta (P. Sherrington, pers. comm).

Migratory Behavior

Diurnal migrant; nonflocking, though > 1 may be sighted during post-fledging period or where prey species are concentrated (Salomonsen 1950, Platt 1976, Cade 1982, Wiseley and Pinel 1987, Dobler 1989, Sanchez 1993).

Control And Physiology

Little information; extent of migration and destination believed to be determined primarily by food availability. Can persist as resident wherever flocking ptarmigan or waterfowl and seabirds occur. Limited satellite and radio transmitter results from Alaska suggest Gyrfalcon fall and winter movements may be influenced by shorebird, waterfowl, or sea bird concentrations in coastal areas. Montane and inland populations may be more likely to migrate (at least locally) than coastal and riparian populations because of greater temporal variation in food supply (Cade 1982, Nielsen and Cade 1990a). Weather influences many prey species and may indirectly affect Gyrfalcon movements. In South Dakota, first Gyrfalcon sightings corresponded with drop in temperature and increase in waterfowl abundance (Sanchez 1993). Wintering birds generally associated with concentrated prey populations (Salter et al. 1980, Dobler 1989, Everett et al. 1989, Sanchez 1993).