Migration

Long distance (often transoceanic) between breeding areas in low arctic North America and wintering range in northern South America. Most yearlings summer in South America and do not migrate north until their second year (Gratto and Morrison 1981, Spaans 1984, Gratto and Cooke 1987, Gratto 1988).

Birds from the eastern Arctic migrate north from South America through the U.S. Atlantic coast. North of Massachusetts to Atlantic Canada, migrants are more common during fall than spring migration. Central and western Arctic breeders migrate north through interior North America. In fall, most western breeders migrate south through the prairies, along with some birds from central arctic populations. Remaining central arctic and eastern breeders return to South America primarily viathe north Atlantic coast of North America, often flying directly over ocean (see Control and Physiology of Migration). Western arctic breeders appear to winter farther west in South America than eastern breeders (McNeil and Burton 1973, Martinez 1974, McNeil and Burton 1977, Hanson and Eberhardt 1978, Harrington and Morrison 1979, Martinez 1979, Spaans 1979, Morrison and Gratto 1979, Lank 1983, Morrison 1984, Lank 1989, H. L. Dickson and C. L. Gratto-Trevor unpubl. data).

Spring migration in continental United States and southern Canada lasts from April to June, normally peaking in mid- to late May (Loftkin 1962, Oring and Davis 1966, Palmer 1967, Bradstreet et al. 1977, Harrington and Morrison 1979, Colwell et al. 1988a). Highest concentrations are found at Delaware Bay, NJ (up to 175,000; Dunne et al. 1982), Cheyenne Bottoms, KS (up to 200,000; Martinez inSenner and Howe 1984), and Quill Lakes, Sask. (up to 50,000; H. Dickson pers. comm.). Peak of northward migration is less protracted than fall peak, even excluding juveniles. Since males arrive on breeding grounds a few days earlier than females, males probably precede females by several days during spring migration (CLG-T).

Adults migrate earlier than juveniles in fall, leading to two migration peaks. Adults start southward in mid-July, reaching maxima in late July to mid-August (McNeil and Cadieux 1972a, Page and Middleton 1972, Weir and Cooke 1976, Bradstreet et al. 1977, Morrison 1984, Hicklin 1987, Dunn et al. 1988, Colwell et al. 1988a). Earliest migrating adults are probably nonbreeders; flocks contain a proportionately high number of yearlings (Gratto 1983, Morrison 1984). During main wave of adult migration, females normally precede males by about 5 days (McNeil and Cadieux 1972a, Morrison 1984), since females normally desert brood earlier than males do (Ashkenazie and Safriel 1979a, b, Gratto and Cooke 1987, Gratto-Trevor 1991). Migration may be timed in relation to decrease in prey availability at staging areas (Boates and Smith 1979, Schneider and Harrington 1981).

Juveniles (young of the year) migrate from mid-July to late October, peaking (normally at lower numbers than adults) between late August and mid-September (McNeil and Cadieux 1972a, Page and Middleton 1972, Weir and Cooke 1976, Bradstreet et al. 1977, Harrington and Morrison 1979, Morrison and Gratto 1979, Morrison 1984, Dunn et al. 1988).

Highest concentrations of this species in central North America found at Cheyenne Bottoms, KS (Martinez inSenner and Howe 1984), and Quill Lakes, Sask. (H. Dickson pers. comm.), but largest flocks in the upper Bay of Fundy; e.g., up to 350,000 at Mary’s Point, N.B. (Morrison 1984, Hicklin 1987). In the Bay of Fundy, these constitute about 95% of all shorebirds and, during fall migration, 40–74% of the world population of this species (Hicklin 1987).

Experimentally, this sandpiper shows strong orientation under clear skies but not under overcast skies, so it appears to use stellar cues in orientation. It probably also uses magnetic cues; experimental orientation behavior under translucent covers changes with rotation of a magnetic field (Lank 1973, D. Lank pers. comm.).

Weather conditions determine departure from staging areas. Birds normally depart southward from fall staging areas in noisy flocks, orienting south or southeast near sunset. Larger flocks orient better. In coastal areas, flocks normally depart near high tide (when foraging areas are inundated) and when winds favor southeastern flight. Flocks usually migrate at night, but also diurnally during long nonstop flights (Lank 1989).

Migratory restlessness increases with the approach of a cold front (Lank 1973). During fall migration, rate of weight gain and departure weight may depend upon the density of invertebrate prey available, and the length of the subsequent nonstop flight. Rate of fat deposition at James Bay, Ont., was estimated at 0.4 g/d (Gratto 1983, Morrison 1984), and in Bay of Fundy at more than 1.0 g/d (P. Hicklin unpubl. data). Invertebrate densities are much greaterin the Bay of Fundy than in James Bay (CLG-T), as are average bird weights (see Appearance: measurements). Average length of nonstop flight from southern James Bay was estimated at 1,100–1,500 km (to east coast of Canada, Gratto 1983), and from Bay of Fundy 4,300 km (to northern South America; Hicklin 1987).

Fat content is apparently a poor predictor of subsequent length of stay at stopovers, even before long nonstop flights (Page and Middleton 1972, Post and Browne 1976, Lank 1983, Morrison 1984, Dunn et al. 1988; but see White 1985, L. White unpubl. data). Estimated arrival and departure weights are much lower for juveniles than adults at James Bay (Gratto 1983) and coastal Maine (Dunn et al. 1988); juveniles arrive in northern South America with very low fat stores, or none (Spaans inGratto 1983). More juveniles than adults marked at James Bay, Ont., were later reported from the Caribbean, suggesting that juveniles cannot fly as far nonstop (Morrison 1984).

Semipalmated Sandpipers probably undertake nonstop transoceanic flights of > 3,200 km from the northeast coast of North America to wintering areas in South America (McNeil and Burton 1973, 1977, Morrison 1984, Hicklin 1987, Dunn et al. 1988). Individuals store larger fat reserves before migrating southward from northeastern Canada than they do before northward flight from Venezuela (McNeil and Cadieux 1972a). According to the flight range formula of McNeil and Cadieux (1972b), using average flight speed of 50 miles/hr (90 km/hr; McNeil 1969), the birds must acquire fat reserves equaling 40% of their fat-free dry weight to make this flight. Many in the Bay of Fundy do acquire sufficient reserves (Hicklin 1987). This formula, however, may overestimate necessary reserves; one bird flew from Maine to South America with only 23% fat (Dunn et al. 1988) within the 40–60 hours necessary for the flight. Flight range estimates were recently reviewed by Davidson (1984) and Castro and Myers (1988).

No data available.