Migration

Nature Of Migration In The Species

Long distance (transoceanic on Atlantic Coast) between subarctic/boreal breeding areas and wintering areas in Central America and n. South America. Migration also occurs across North America; diffuse, with migrants less dependent on key staging sites than most other calidridines.

Timing And Routes Of Migration

Migrates on wide fronts across North American interior and along both coasts (Cramp and Simmons 1983). On Atlantic Coast shows elliptical pattern of migration, common to several other Calidris sandpipers, with fall migrants moving south overseas and spring migrants returning north through s. U.S. (McNeil and Cadieux 1972a, McNeil and Burton 1977).

Spring migrants return relatively late, with large numbers still on winter range in Surinam in early May (Spaans 1976). Peak northward movement across U.S. 1–20 May, through eastern and central Canada late May (Palmer 1967, Colwell et al. 1988), in Washington and British Columbia mid-Apr to mid-May (Campbell et al. 1990, Paulson 1993). Early spring migrants appear in coastal Oregon (Paulson 1993) and s. coastal British Columbia by mid-Mar (Campbell et al. 1990), s. Alberta in late Apr (Semenchuck 1992), Cape May, NJ, and Massachusetts by mid-Apr (Urner and Storer 1949, Veit and Peterson 1993), w. Alaska by 10 May (Petersen et al. 1991), and Churchill, Manitoba, by 25 May (Littlefield and Pakulak 1969).

Peak migration 1–2 wk earlier on Pacific Coast than elsewhere (see Campbell et al. 1990, Paulson 1993). Early breeders return in early May on Queen Charlotte I., British Columbia, whereas far northern (probably) breeders are still in South America (Cooper 1993). Late spring migrants linger until late May or early Jun (Loftin 1962, Paulson 1993). A few nonbreeders remain regularly through Jun and Jul on winter range (McNeil 1970, Spaans 1976, 1978, Hilty and Brown 1986, Styles and Skutch 1989).

Also rare migrant to Arctic coastal plain (Johnson and Herter 1989) and w. Greenland (Am. Ornithol. Union 1957).

Spring migrants move from ne. South America through Caribbean and up North American Atlantic Coast or through Mississippi Valley, without long transoceanic flights associated with fall migration (McNeil 1970, McNeil and Cadieux 1972a, McNeil and Burton 1977). Spring migrants 5 times more numerous than fall migrants through Arkansas (Smith et al. 1991), but less numerous at Lake Erie, Cape May, NJ, and Missouri (Urner and Storer 1949, Bradstreet et al. 1977, Hands et al. 1991).

Most abundant small shorebird during spring (mid-May to early Jun) and fall (mid-Jul through Aug) migration in Ogilvie Mtns., Yukon (Frisch 1982), second most abundant fall migrant on Magdalen I., Quebec, and Sable I., Nova Scotia (McNeil and Burton 1973, 1977). Numbers peak at Nelson Lagoon, central Alaska, in late Jun (Gill and Jorgenson 1979).

During fall movement, adults migrate earlier than juveniles, leading to 2 migration peaks (Page and Bradstreet 1968, McNeil and Burton 1973, Page 1974, Cramp and Simmons 1983, Miller 1983a, Paulson 1983, 1993, Cooper 1993, Butler and Kaiser 1995). Adults start southward in late Jun, reaching maximas in early to late Jul in s. Canada (Page and Bradstreet 1968, McNeil and Cadieux 1972b, Bradstreet et al. 1977, Colwell et al. 1988, Campbell et al. 1990, Butler and Kaiser 1995). Adult females that successfully bred leave Queen Charlotte Is. 23 Jun-8 Jul, successful males 30 Jun-1 Aug, juveniles mid-Jul to mid-Aug (Cooper and Miller 1997). On Fraser River delta, British Columbia, adults present between late Jun and late Jul, peak numbers in second week of Jul, with a few stragglers remaining to mid-Sep; juveniles arrive between mid-Jul and mid-Sep, with peak in second week of Aug (Butler and Kaiser 1995). During early and peak adult migration, females normally precede males (McNeil and Cadieux 1972a, Page 1974, Bradstreet et al. 1977); females desert broods earlier than males do (Miller 1985, Cooper 1993), a widespread trend in scolopacids.

First adults arrive Long Point, Ontario early Jul, Washington about 20 Jun, peaking in Pacific Northwest early Jul; adults are mainly gone when juveniles arrive (Page and Bradstreet 1968, Paulson 1983, 1993). Adult fall migrants arrive 30–40 d before juveniles at Bolinas Lagoon, CA, with 2-yr-olds slightly later than older adults (Page 1974). Juveniles peak early Aug to early Sep in British Columbia and Washington (Campbell et al. 1990, Paulson 1993) and at Lake Erie (Bradstreet et al. 1977). Peak movement of adults in Bay of Fundy late Jul (Hicklin 1987); of adults and juveniles on Magdalen I. mid-Jul to early Aug and mid-to late Aug, respectively; on Sable I. mid-and late Aug, respectively (McNeil and Burton 1973). First adults arrive Surinam mid-Jul, most in Aug, first juveniles mid-Aug, with arrivals continuing through Oct (Spaans 1976, 1978, 1979). Late northern juveniles seen as late as 25 Sep at sw. Hudson Bay (Manning 1952).

Fall migrants staging in California disperse southward in Nov, leading to smaller, more stable winter populations, probably because of a decline in primary food species; about 25% of banded birds present at Bolinas Lagoon between Aug and mid-Oct wintered there (Page 1974).

Fall migrants banded in James Bay move to staging areas in s. Ontario, Maritime Provinces, and New England states (Morrison 1978). Bay of Fundy is last major staging area for most birds moving down Atlantic Coast (Hicklin 1987). Fall migrants and breeders banded on Sable I., Nova Scotia, and Magdalen I., Quebec, move down Atlantic Coast as far as Massachusetts before embarking on transoceanic migration to Lesser Antilles and ne. South America, a distance of about 3,200 km (McNeil 1970, McNeil and Burton 1973, 1977).

Migrants departing overseas from Maritimes Provinces and New England likely winter in Lesser Antilles and ne. South America (McNeil and Cadieux 1972a, McNeil and Burton 1973). Migrants moving through interior North America winter in s. U.S., Greater Antilles, Gulf of Mexico, and nw. South America (McNeil and Cadieux 1972a, McNeil and Burton 1973, Cramp and Simmons 1983). Pacific Coast migrants presumably winter south to Peru. Widespread and locally common migrant (Aug–Oct) in Costa Rica, where much more numerous on Pacific than Atlantic Coast (Styles and Skutch 1989).

Differential Migration

Females spend nonbreeding season further south than males as shown by sex ratio data from California, Surinam, Panama and Ecuador; no difference found in age ratios (adults and 1st-year birds) among those sites (Spaans 1976, Nebel 2006). Differential migration according to bill and wing length see Systematics: geographic Variation.

Migratory Behavior

Poorly known. Gregarious during migration, occurring in flocks of dozens to hundreds, occasionally thousands, at key staging sites (Paulson 1993, Veit and Petersen 1993). Spring migration more rapid than fall (Paulson 1983, 1993, Smith et al. 1991, Davis and Smith 1998b). Stops at staging areas for varying durations, shorter in spring, longer in fall. Fall migrants on Sidney I., British Columbia, staged for minimum average of 5 d (range 1–18 d), 2 d longer than Western Sandpipers (Butler et al. 1987, Butler and Kaiser 1995).

Fall inland migrants may pause from 1 wk to 1 mo to replenish fat reserves (Oring and Davis 1966, Recher 1966, Post and Browne 1976).

Migrates from coast to inland areas along major river valleys or mountain corridors (McNeil and Cadieux 1972a, Frisch 1982, Petersen et al. 1991).

Control And Physiology

On Sable I., Nova Scotia, successful breeders depart breeding areas sooner after broods fledge than do unsuccessful breeders (those losing a clutch and not replacing it; 3 vs. 7–10 d). In contrast, unsuccessful breeders depart sooner late in breeding season; in general, unsuccessful females depart sooner than unsuccessful males (Miller 1983a).

Spring migrants in ne. Venezuela had enough fat to fly 1,800–2,600 km; lower levels than for fall Atlantic migrants, but sufficient for return over Caribbean to Florida or Gulf Coast (McNeil 1970). Spring migrants from n. South America moved along Caribbean islands to North America due to prevailing easterly winds, which hinder direct flight over Atlantic Ocean (Bellrose and Graber 1963).

Adults on Magdalen Is., Quebec, in late Jul to mid-Aug have fat levels sufficient to fly nonstop 2,600–2,900 km, with some capable of up to 3,600 km, significantly higher fat levels than wintering birds have for spring movement. Heaviest birds capable of transoceanic flight from Gulf of St. Lawrence to n. South America. Leaner adults and juveniles need to stage and fatten in Maritime Provinces or New England before starting oversea flight of about 3,200 km, or work down Atlantic Coast before crossing Caribbean (Page and Salvadori 1969, McNeil and Cadieux 1972a, McNeil and Burton 1973, 1977). In interior U.S., flight range capability estimated at 1,700–3,200 km for individuals with moderate to heavy fat loads, sufficient to reach South American wintering areas. Leaner birds, flight range of 500–1,200 km, were capable of reaching coastal areas in se. U.S. (Post and Browne 1976). Peak fall migration in Bay of Fundy coincides with peak abundance of primary prey, the amphipod Corophium volutator (Hicklin 1987).

Flight speeds estimated at 75–83 km/h (McNeil 1969); thus birds flying nonstop from Bay of Fundy would arrive Surinam in about 70 h (Morrison 1984). Numerical formula for estimating flight range are in McNeil and Cadieux 1972b, but see Weber and Houston 1997 for review. Fat equal to about 30% of fat-free weight is required to fly about 3,200 km (McNeil 1969).

On Fraser River delta, British Columbia, mean weights of fall migrant adults and juveniles increased between first and third week of migration but declined during last week of migration (Butler and Kaiser 1995). Most rapid weight gains occurred between second and third weeks Jul for adults (0.15g/d) and second and third weeks Aug for juveniles (0.04g/d). Rate of weight gain by Western Sandpipers in same habitat was ≥ 60% higher. Although there were no age-related differences in body mass, age-related differences in weight gains were thought to be related to lower tides and longer foraging periods during Jul. Body masses of migrants did not differ between saltmarsh, riverine marsh, and sewage lagoon habitats (Butler and Kaiser 1995). Weights of spring and fall migrants were not different, which contrasts with species such as Western Sandpiper that are heavier in spring (Butler and Kaiser 1995).

At Long Point, Lake Erie, fall staging juveniles gained 0.71 g/d of fat during stopovers (Page and Salvadori 1969). Three fall migrants in inland N. Carolina, recaptured 7 d later, gained 3.2 g (10.7%), 5.9 g (22.4%), and 5.2 g (26.0%), respectively, whereas a bird recaptured after 20 d gained only 2.6 g (13.7%) (Post and Browne 1976).