Migration

Nature Of Migration In The Species

Most are short to intermediate distance migrants depending on breeding and wintering latitudes; birds potentially resident in southern portions of range, but recent analysis of band recoveries suggests many southern breeders and fledglings may move north after breeding (Lemon 2004, Pearce et al. 2008). Some birds winter as far north as ice permits. Band recovery data, largely for females, indicate 80% of birds banded in Maine, Vermont, New Hampshire, and New York were recovered in coastal Atlantic states from New Jersey to Florida, the remaining 20% from Ontario and Quebec (n = 85). In contrast, 87% of mid-continent birds banded in Minnesota, Missouri, and Wisconsin were recovered in the Mississippi Flyway, including e. Texas, (n = 26), 6.5% in the Atlantic Flyway (n = 4), and 6.5% in the Central Flyway (n = 4; BDD). Although data are lacking, birds breeding west of the Rockies appear to migrate west and south towards the Pacific Ocean (e.g., Campbell et al. 1990).

Timing And Routes Of Migration

Late migrants in fall; some individuals moving just ahead of winter ice. Birds recovered from Ontario and Quebec as late as Nov and birds remain along coastal New Brunswick at least until Jan (BDD, Root 1988). During fall, peak numbers of migrants occur the last week of Oct/first week of Nov in Minnesota (M. Zicus pers. comm.) and the last week in Nov/first week in Dec in Missouri (LHF); possibly reaching winter areas by following large river drainages. In the east, peaks occur in mid-Nov in New England and late Dec in Florida (Bellrose 1976). Peak departures from interior British Columbia birds occur the third week of Oct (Campbell et al. 1990), and birds begin arriving on wintering areas in California and the Pacific Northwest in mid-Nov (Bellrose 1976).

Early migrants in spring, often arriving on breeding areas within days of ice out. In the southeast, birds begin leaving wintering areas in early Feb, but in the Pacific Northwest, birds remain on coastal winter areas until mid-Apr (Campbell et al. 1990). Arrivals on breeding areas range from early Feb in se. Missouri (LHF) to late Mar in the Great Lakes region (Bellrose 1976), and mid- to late Apr in British Columbia (Campbell et al. 1990) and Quebec (Renouf 1972).

Migratory Behavior

Flight flock sizes, flight speed, and nonstop flight distances unknown. Thought to migrate singly, in pairs, or in small flocks, often at night (Bellrose 1976). Campbell et al. (1990) describes fall migration in British Columbia as “a gradual dispersal” with small numbers of birds continuously leaving post-breeding areas. Concentrations during fall migration variable; but typically larger than spring. Largest flock sizes reported include 225 on Ludlow reservoir, MA, Nov 1964 (Veit and Petersen 1993), and 730 on Pelican lake, MN, Nov 1993 (M. Zicus pers. comm.). Flocks of 30–40 more common in Missouri (LHF).

Control And Physiology Of Migration

No information available.