Migration

Few direct observations of migration in North American birds. Northeastern individuals are long-distance migrants traveling mainly over ocean to West Indies and South America; no information about migration routes of individuals breeding in Caribbean region. Migrants observed with dense flocks of Common Terns on beaches in Trinidad in spring (MG). Factors influencing migratory movements not known. Juveniles and adults disperse in family parties throughout breeding range in late Jul and Aug. Most 1-year-olds remain in winter quarters during boreal summer (Nisbet 1984), but a few banded 1-year-olds have been observed at northern breeding colonies (ICTN). Patterns of postbreeding dispersal, staging, and migration essentially unknown for Caribbean birds, but some 1-year-olds also recorded at Caribbean breeding colonies (Shealer and Burger 1995). Movements of European populations summarized in Cramp 1985 .

Spring

Northbound route of northeastern population uncertain. Large flock of Roseate and Common terns seen off southern coast of Trinidad, West Indies, in early Apr 1965 (MG); probably migrants. Northeastern birds migrate offshore; recorded off N. Carolina uncommonly in May (D. Lee in litt.); vagrant in Bermuda (Amos 1991), first arriving at Nantucket and Martha’s Vineyard, MA, in large flocks, then dispersing northward as well as westward. Arrive 26 Apr–20 May at Bird I., MA (Nisbet 1980, 1981a, 1989), slightly later at Falkner I., CT, and Great Gull I., NY, and finally at Cedar Beach, NY. Nonbreeding subadults and first-time breeders arrive after mid-Jun, continuing to arrive until mid-Jul (J. Spendelow pers. comm., ICTN). Occasional spring migrant on N. Carolina Outer Banks. Records from S. Carolina rejected (McNair and Post 1993), and almost completely unknown in Georgia. At most northerly breeding site at Madeleines in Québec, has been recorded between 19 May and 11 Sep (Gauthier and Aubry 1996).

Postbreeding Dispersal

Staging birds reported in large flocks with other terns at inlets and islands from Long I., NY, to Maine in Aug–Sep (Veit and Petersen 1993, Shealer and Kress 1994). Main movement from colonies in northeasterly direction (Nisbet 1984, Shealer and Kress 1994), with concentration at Monomoy I., MA, just before departure in mid-Sep (Nisbet 1989), when most birds leave staging areas within a few days (ICTN); few records after late Sep (Veit and Petersen 1993).

Fall

Apparently migrates directly across w. North Atlantic to West Indies (Nisbet 1984). Regular at sea off N. Carolina late Aug to late Sep, peak in early Sep; latest date 28 Oct (D. Lee in litt.). Band recoveries are mainly in West Indies from Hispaniola to Trinidad in Sep and early Oct, in Trinidad and Guyana Oct–Nov (few in midwinter), and in Brazil from Nov onward (Nisbet 1984, Hays et al. 1997). Flocks seen migrating south in e. Caribbean in Oct (R. van Halewyn in Nisbet 1984).

Vagrancy

Rarely seen in spring or autumn on U.S. coast south of New Jersey; most states report few records (Clapp et al. 1983). Vagrant inland; unconfirmed band recovery from Indiana (Nisbet 1984). Three records from Niagara region, New York. Only evidence of trans-Atlantic movement was a bird banded as a chick at Rockabill, Ireland, and encountered as a 2-yr-old at Bird I., MA (but no evidence that it bred; Nisbet and Cabot 1995).

Caribbean Population

Arrives at breeding colonies in late Apr and early May, and departs mainly from early Sep (Dry Tortugas; Robertson 1978) to Oct (Puerto Rico; J. Saliva pers. comm.). Recently found wintering with northeastern Roseates on coast of Bahia, Brazil (Hays et al. 1997).

No formal studies. Migrates in flocks, probably with Common Terns. Little information on speed of migration. A banded bird was recovered in Colombia 24 d after its last sighting in Connecticut (Hays 1971). No information on height of migration or on whether this species is nocturnal. Presumably flies long distances between staging areas, where it rests and feeds (e.g., Guyana) before continuing.

No information on control of migration. Depends on small prey fish, so northward migration may depend on prey availability. Migratory patterns outside breeding season may depend on location of schools of predatory fish that force prey fish to surface. Departure of European birds from w. African wintering area closely associated with rise in sea temperature, and growth and dispersal to deeper water of small fish (A. J. del Nevo pers. comm.).