Migration

Most individuals breeding on Atlantic Coast north of S. Carolina are migratory. South of this area, observed in breeding range throughout year, although numbers decline in some areas during winter (e.g., S. Carolina, Louisiana, n. Florida). Latitude of wintering site may vary considerably, with many migrants remaining in se. U.S.; others continue to Caribbean or Central and South America, where northern birds are thought to overlap extensively with southern races during winter. On Yucatán Peninsula (Sian Ka’an Biosphere Reserve located on Caribbean coast), only about 20% of the birds present during peak winter counts were present in summer, suggesting that many winter birds are migrants from elsewhere (Lopez-Ornat and Ramo 1992). Greatly increased sightings during Apr and May in n. U.S. and Canada since 1940 suggest that birds sometimes overshoot intended target when migrating northward. After breeding, individuals wander widely both along coasts and inland to upper Midwest, sw. U.S., and s. Canada (see below).

Little information on routes of migration. Observations of offshore migrants and banding recoveries indicate that birds move between Florida and Cuba and between Florida and Central America. Regular appearance of migrants in Bermuda indicates this species’ capacity to cross large expanses of water. Birds wintering in s. California might originate from breeding areas in Baja California, thus wintering north of their breeding grounds. Timing of migration difficult to determine in many areas because species is present throughout year in all but northernmost portions of breeding range. Some individuals (possibly immatures) remain in Central American winter range throughout year.

In Panama, casual observation suggests departure northward in Feb (Wetmore 1965). Transients have been recorded on Bermuda 25 Mar–21 May (Amos 1991). Spring migrants (as indicated by offshore migrants, tower kills, etc.) observed in n. Florida by early or mid-Mar (Stevenson and Anderson 1994). Arrive in Maryland mid- to late Apr (Robbins 1996); Cape May, NJ, last week of Apr (Sibley 1993); and Massachusetts late Apr–early May (Veit and Petersen 1993). Wandering birds may appear during spring north of regular breeding areas.

In northern midwestern states and Canada, numerous sightings after 1970, during Apr–early Jun (Bull 1985, Janssen 1987, Bolen 1989, Peterjohn 1989, Robbins 1991, Veit and Petersen 1993).

After breeding season, individuals wander in many directions, particularly northward. After breeding, birds disperse both along coast (Willlard 1977, Telfair 1979) and inland, sometimes long distances. Sightings in mountains of N. Carolina, Virginia, inland Massachusetts, Tennessee, Ohio, Arkansas, Missouri, Kansas, Oklahoma, Colorado, inland Texas, New Mexico, and Arizona during Jul and Aug. In Canada, sightings and occasional records in southern reaches of all provinces except British Columbia and Prince Edward I. (Godfrey 1986). In Ohio, rare but regular to w. Lake Erie marshes (Peterjohn 1989). In California, has been recorded north to Sonoma and Lassen Cos. (Small 1994). Strays occur widely along watercourses of interior, sw. U. S., including: Arizona north to Camp Verde (Yavapai Co.); s. New Mexico; e. Colorado; central and w. Texas, along Rio Grande; lower Colorado River; and Salton Sea—all mainly between Apr and Aug (Phillips et al. 1964, Oberholser 1974, Andrews and Righter 1992). In Colorado, sightings peak in May. Occasionally wanders south to Chile on Pacific Coast of South America (Araya and Chester 1993).

In fall, moves south from breeding grounds in U.S. to wintering grounds in Caribbean and Central America; timing less clear than in spring. “Flybys” peak in Cape May, NJ, Aug–Sep (Sibley 1993); most birds leave Maryland by late Sep or early Oct (Robbins 1996). Regularly recorded in Bermuda early Sep–mid-Nov, occasionally as early as 5 Aug (Amos 1991). Timing of migration outside of ne. Atlantic Coast difficult to determine because of species’ variable presence throughout year.

Birds banded in se. U.S. have been recovered in Honduras, Nicaragua, Florida, Greater and Lesser Antilles, Venezuela, Colombia, and Panama; most recoveries from individuals banded in Texas are from Mexico and Central America (PCF). All sightings at northernmost edge of western range, in San Diego Bay, CA, are during winter (Dec–Feb), suggesting northward movement in fall and winter (Grinnell 1928, Cogswell 1977, Garrett and Dunn 1981). Will migrate over water: observations of birds at sea (eastern coast of Florida; Stevenson and Anderson 1994); apparent arrival of trans-Gulf migrants in spring (S. Cardiff unpubl. data); regular occurrence at Bermuda and other isolated islands in Caribbean (see Distribution, above).

No information.

No information.