Migration

Partial migrant; most birds from northernmost breeding locations probably abandon these areas during winter, while populations farther south show varying degrees of migratory behavior. Populations from Nova Scotia, and Cape Ann and Boston, MA, remain around breeding colonies throughout year, whereas birds from Maine, Gulf of St. Lawrence, and Newfoundland disperse southward, wintering along mid-Atlantic Coast (Powers 1983) or in Great Lakes region (Southern 1980). Populations from St. Lawrence Seaway disperse to Great Lakes; Great Lakes breeders remain around breeding colonies or move to St. Lawrence Seaway. Populations in se. Massachusetts and mid-Atlantic Coast appear to move south along coast. Southernmost breeding populations do not migrate, remaining near colonies.

In s. Newfoundland, most breeders leave colonies in late Aug, moving offshore (50–100 km) to deeper waters, where they remain until early Apr. Banded gulls from Bay of Fundy move north into Northumberland Strait after breeding; some spend winter months on New Brunswick coast; make long-distance southward flights up to 2,360 km during same period and through winter (Astle and McAlpine 1985). Band recoveries in Great Lakes indicate that birds wintering on Great Lakes originate from colonies in St. Lawrence Estuary and Maine (Angehrn et al. 1979).

Dispersal may begin as early as late Jul; some leave breeding areas in mid-Aug (Bent 1921). In Bay of Fundy, banded nonbreeders appear migratory; many banded adults remain near breeding grounds throughout year (Astle and McAlpine 1985). Banded adults and subadults range westward to Great Lakes; banded juveniles range farther south to Florida and Georgia (Southern 1980). In late fall and winter, massive dispersal from coastal breeding colonies to offshore fishing areas (Powers 1983); remain in Atlantic boreal and low-Arctic waters all winter, but farther offshore and farther north (Brown 1986). Other individuals disperse south to areas of open water in fall. Subadults concentrate along s. Atlantic Coast during winter (Southern 1980). In spring, immatures and subadults are common in shelf waters in Gulf of Maine, Georges Bank, s. New England, and mid-Atlantic areas north and east of Hudson Canyon (40°N). Majority of band recoveries are from se. Canada and ne. U.S.; significant proportion of Great Black-backed Gulls winter in that region; mean distance between banding and recovery sites for Dec–Mar was 350–580 km (Southern 1980).

Fall dispersal and migration mainly Sep–Oct (Southern 1980). In s. Quebec, peak of fall southward migration 27–31 Dec (>500 birds/d), peak migration month 14 Dec–14 Jan (Steeves et al. 1989). In Ohio, arrive in Western Basin of Lake Erie 20 Aug–5 Sep; flocks >10–30 unusual before early Nov. Casual visitors to Central Basin Aug and Sep; not a regular until Oct (Peterjohn 1989). In Illinois, arrive Nov or Dec; earlier records 22–26 Aug, 13 Sep, 7–9 Nov (Bohlen 1989). In Missouri, 1 fall record; immature observed 7–8 Nov (Robbins and Easterla 1992). In S. Carolina, visitor from 12 Nov (Clapp et al. 1983). In Georgia, visitor from Dec (Clapp et al. 1983). In Florida, visitor from Oct (Robertson and Woolfenden 1992). In Alabama, observed from 5 Nov (Clapp et al. 1983). In Texas, casual from Oct (Rappole and Blacklock 1994).

Spring migration mainly Mar–Apr (Southern 1980). Casual in Texas until Apr (Rappole and Blacklock 1994). In Alabama, observed until 24 Apr (Clapp et al. 1983). In Florida, visitor through May (Robertson and Woolfenden 1992). In Georgia, visitor until Mar (Clapp et al. 1983). In S. Carolina, recorded through 12 May (Post and Gauthreaux 1989). In Missouri, 2 spring records; adults observed 27 Feb and 17 Mar (Robbins and Easterla 1992). Departure from Illinois coincides with ice breakup; later records 7 Apr, 20 Apr (Bohlen 1989). In Ohio, depart from w. Lake Erie mid-Apr and Central Basin late Mar; some immatures regularly encountered into Apr and May (Peterjohn 1989). In s. Quebec, mean arrival during spring northward migration 3 Apr, earliest migrant arriving 5 Mar (Steeves et al. 1989).

Some young remain with parent(s) for several months after fledging; pairs with chicks observed foraging in intertidal zones in winter (TPG). Juvenile and immature birds congregate around areas where food can be obtained reliably—e.g., intertidal areas, fishing boats, refuse dumps. Adults (often accompanied by immatures) found at sea near Georges Bank and Gulf of Maine Sep through Apr (Powers 1983).

Most subadults do not return to natal colony during breeding season; may spend summer in part or all of winter range (Bent 1921). In summer, largest proportion of all age classes is near breeding sites; mean distance between banding and recovery locations 164 km in Jul (Southern 1980).

No data. Offshore movement apparently related to foraging conditions. Many adults offshore in Mar are building reserves for breeding season; move onshore in Apr to breed (Brown 1986). Immatures move to milder (less energetically stressful) southern climates when cold weather starts (Oct–Mar; Root 1988).