Migration

Short- to medium-distance migrant; individuals present year-round in all but the most northerly coastal breeding areas, but all inland breeding locations (except Central Valley and Salton Sea in California and Presa Marte R. Gómez in ne. Mexico) deserted during winter. Also postbreeding dispersal to areas north and south of breeding areas. For their first summer, most immatures remain within species’ wintering distribution. In general, spring migration earlier and fall migration later than that of Common Tern.

Spring

Sonora, Golfo de California: departs Mar–early Apr (Russell and Monson 1998). Along lower Colorado River of s. Arizona and s. California, un-common migrant from late Apr to May (Rosenberg et al. 1991). California, central coast: migration occurs early Apr–late May, peaks 24 Apr–13 May (Shuford et al. 1989).

Kansas: earliest 6 Apr, most arrivals after 15 Apr (Thompson and Ely 1989). Iowa: late Apr–early May, as early as 7 Apr (Kent and Dinsmore 1996). Minnesota: early Apr–mid-May (Janssen 1987). Illinois: average spring arrival Cook Co., 29 Apr (n = 8 yr); for Sangamon Co., 15 Apr (n = 18 yr; Bohlen 1989). Wisconsin: mid-Apr–early Jun, as early as 5 Apr (Robbins 1991). Manitoba: early to mid-May (McNicholl 1971). Alberta: early May (Semenchuk 1992). British Columbia, interior: mid- to late May (Campbell et al. 1990).

Florida: most numerous through Apr; movements of migrants masked by presence of nonbreeding residents (Stevenson and Anderson 1994). Delaware: usual arrival early Apr, peaking mid-Apr (Hess et al. 2000).

Fall

California, central coast: migration mid-Jun to mid-Oct (Shuford et al. 1989). Along lower Colorado River of s. Arizona and s. California, from Jun to mid-Oct with peak mid-Jul–mid-Aug (Rosenberg et al. 1991). Sonora: Sep–early Oct (Russell and Monson 1998).

Alberta: departs by late Sep (Semenchuk 1992). Manitoba: departs by mid-Sep, as late as 15 Oct (Grieef 1994, MKM). Wisconsin: migration early Aug–mid-Oct, as late as 8 Nov (Robbins 1991). Illinois: average fall arrival Sagamon Co., 17 Jul (n = 17), and departure 14 Oct (n = 18 yr; Bohlen 1989). Minnesota: migration Aug–early Oct (Janssen 1987). Iowa: migration late Aug–Sep, as late as 9 Nov (Kent and Dinsmore 1996). Kansas: earliest 21 Aug, most between 7 Sep and 22 Oct, latest 28 Nov (Thompson and Ely 1989).

Often remains in large numbers in Delaware through mid-Dec, but most birds remaining after mid-Dec depart by 15–20 Jan (Hess et al. 2000). N. Carolina: migration from late Jul to Nov, peaking late Aug–Oct (Clapp et al. 1983). Georgia: migration peaks in Nov (Clapp et al. 1983). Florida: migration as early as mid-Jul, migrants joining resident individuals in Aug (Stevenson and Anderson 1994).

South of U.S. and Mexico, transients recorded 18 Aug–2 Sep and 27 May in Bermuda while wintering birds recorded 10 Nov–11 Feb (Amos 1991). Recorded wintering Nov–Apr in West Indies (Raffaele et al. 1998), Nov–Feb in Costa Rica (Stiles and Skutch 1989), and Nov–Mar in Panama (Ridgely and Gwynne 1989).

Migrates in small groups generally but larger concentrations reported (e.g., 1,400 on 13 May 1989, Monroe Co., IN [Peterjohn 1989] and 3,000 in Aug, Malheur National Wildlife Refuge, OR [Gilligan et al. 1994]). Generally assumed to limit its migratory flights to near shore (in coastal areas); recorded 15 km offshore (Briggs et al. 1987). Observations of fledged juveniles begging for food in Florida (Ogden 1969), where breeding is not known, suggest that parental care may continue after migration, as is true for other tern species.

No information.