Migration

Long-distance migration (partly transoceanic) between breeding grounds in Arctic and wintering grounds; latter ranges from s. British Columbia in the west, and se. U.S. in the east, to southern tip of South America. Separate routes for western and eastern breeding populations, with apparently little mixing; further study is needed. Fall migration begins in Jul as soon as first birds lose nests or successful females leave unfledged young (W. Lin pers. comm.). Birds move to coastal areas—Alaska in the west and Canadian maritimes in the east (also New England and southward)—to put on fat; staging coincides with summer abundance of intertidal prey and of berries in ericaceous heaths (Tufts 1961). Most adults pass through coastal regions in Jul and Aug, young in Sep. Most yearlings summer in parts of winter range (Cramp and Simmons 1983), possibly also 2-yr-olds; may not return to breeding areas until third year (Skeel 1983).

Northbound

Movement Mar (sometimes Feb) through May.

Western Population. Birds from west coast of South America migrate along Pacific Coast; some take transoceanic route from about Ecuador, bypass Central America, and rejoin coastal route in Mexico or California (Schneider and Mallory 1982, Morrison and Myers 1987); others may cross isthmus of Panama and Caribbean to se. U.S. (Taverner 1942). Migrants pass through Peru in Mar and Apr (Johnson 1972); influx occurs along Central American coast mid-Mar to early May (Stiles and Skutch 1989), sometimes as early as Feb (Delgado and Butler 1993).

Transient along coast of California in Mar, Apr, and early May; large flocks in interior California in late Apr; in coastal nw. U.S. and s. British Columbia, numbers build in mid-Apr, peak in mid-May (Campbell et al. 1990, Harrington and Page 1992, Paulson 1993, Lehman 1994). From there, birds fly directly to Gulf of Alaska, especially Cook Inlet, where they are common in mid-May; however, scattered observations along intervening coast (Gibson 1970, Campbell et al. 1990, West 1993). Presumably fly over mountains to n. Alaska and Mackenzie River Delta (Kessel and Cade 1958, Irving 1960). A few records in interior British Columbia and sw. Northwest Territories suggest small inland migration.

Eastern Population. Route of birds from southeastern coast of South America unknown. Likely fly across interior following major north-south rivers; not recorded in coastal Brazil from Salvador north to Parnaíba River. Interior route documented for other shorebird species (Antas 1983). Tierra del Fuego birds likely join Pacific Coast migrants (Sick 1993). Large wintering population from north coast of South America (peaking Nov–Jan), and migrants from farther south, fly over Caribbean (but regularly a few records for Bermuda and West Indies) to coastal se. U.S.; common there from Mar to mid-May (Harrington and Page 1992). Birds from e. Central America follow coast or cross Caribbean to U.S.

Stage along Gulf and Atlantic coasts north to New Jersey; regularly a few farther north (Harrington and Page 1992). Numbers build from Mar to early Apr in the s. U.S., and mid-Apr to mid-May from the Carolinas north. No evidence of migration through interior from Gulf or s. Atlantic states. From mid-Atlantic states, birds fly to e. Arctic via Great Lakes; in late May many seen on northern coasts of Lakes Erie and Ontario, and at James Bay (Bull 1974, Speirs 1985).

Southbound

Movement late Jun through Oct.

Western Population. Birds in w. Arctic stage from mid-Jul to late Aug (nonbreeders from late Jun) in coastal Alaska from Kotzebue Sound to Alaska Peninsula (Handel and Dau 1988); some on Bering Sea Is. and Kenai Peninsula (West 1993). Flocks up to 1,000 birds forage on mudflats of Alaska Peninsula (Gill and Handel 1981). Birds then cross Pacific to coastal British Columbia and nw. U.S. (R. Gill pers. comm.); peak late Jun to mid-Aug, but extend into Oct (Paulson 1993). Migrants pass through s. California in Jul and Aug (Lehman 1994); appear on Pacific Coast of Costa Rica in Aug and Sep (Stiles and Skutch 1989), in sw. Peru from Sep to Nov (Johnson 1972).

Eastern Population. Birds leave e. Arctic crossing Ungava Peninsula or ne. Manitoba from early Jul to Aug (Todd 1963, MAS); peak at Churchill, Manitoba (MB), in last 2 wk of Aug, after which rare (Jehl and Smith 1970). Various routes from Ungava and James Bay to Atlantic Coast. Abundant in coastal Labrador, Newfoundland, and Gulf of St. Lawrence from early Jul through Aug (Peters and Burleigh 1951, Morrison et al. 1994a); less common in other maritime areas and New England from mid-Jul through Sep (Morrison 1984, Harrington and Page 1991). Occasionally sighted in Great Lakes from mid-Jul to mid-Oct (Bull 1974, Speirs 1985).

From coastal Canada and New England, many birds fly directly over Atlantic to Caribbean and South America (Morrison 1984). Regular in Bermuda primarily from mid-Aug through late Sep (Amos 1991). Some move south along e. U.S. coast and U.S. Gulf coast: through mid-Atlantic states from mid-Jul to mid-Aug; in the Carolinas from mid-Jul to mid-Sep; in Georgia, Florida, and Alabama from mid-Jul to mid-Oct; and in Louisiana and Texas from mid-Sep to mid-Oct (Harrington and Page 1991). Birds wintering farther south fly over Caribbean or along Gulf Coast, arriving in Central and South America in Aug and Sep (Stiles and Skutch 1989, Rodrigues 1993); occasionally seen in Bahamas, Trinidad, and Tobago in Sep and Oct (Herklots 1961, Brudenell-Bruce 1975). Route to southeastern coastal areas of South America unknown; from Salvador Bay, Brazil, appear to take overland shortcut (Antas 1983).

Spring migration is relatively fast and direct, but birds stage prior to nonstop flights to breeding grounds (Gill and Handel 1981, Harrington and Page 1992).

Fall migration lasts 2–3 mo, with birds staging to accumulate premigratory fat (Gill and Handel 1981). Mean flock size over Yukon-Kuskokwim Delta, AK, in Jul and Aug 3.4 ± 0.46 (SE) birds (n = 163 flocks); birds congregate into larger flocks of 20–30, sometimes up to 1,000, on coastal mudflats and shores (Gill and Handel 1981, Handel and Dau 1988). Near Churchill, MB, feeding flocks number 15–20 birds (Jehl and Smith 1970); passing flocks often number >40 birds (MAS). In Massachusetts, flocks number 15–40 birds (Veit and Petersen 1993).

Sex and age departures from breeding areas need further study. Females appear to migrate before males: at Churchill, MB, females desert mate and young as early as 12 Jul; not seen in breeding area after this (W. Lin pers. comm.). Adults appear to migrate before juveniles: in Massachusetts, adults peak from late Jul to early Aug, juveniles in Sep (Veit and Petersen 1993). Migration in Alaska is bimodal: peaks mid- to late Jul and again in late Aug; sex and age compositions unknown (Handel and Dau 1988).

Adults are wary but decoy to whistled call notes; juveniles are relatively tame (once called “foolish curlew” by hunters; Mackay 1892). Migrating flocks fly in strings or Vs, especially when high; sometimes in irregular bunches (Peters and Burleigh 1951).

In Banc d’Arguin, Mauritania, wintering flocks of N. p. phaeopus usually departed 1–3 h before twilight, regardless of tide cycle; 29% of 62 flocks re-alighted (Piersma et al. 1990). Most flocks vocalized (23 of 24); average climb rate was 0.21 m/s (lower than for most species); headings compensated for wind drift.

Control of departure from wintering grounds in Americas unknown. However, flight range estimated at >4,000 km for birds departing at 40% fat/total body mass at flight speed of 75 km/h (Castro and Myers 1989); more than sufficient for transoceanic portions of migration route.

Birds wintering in Banc d’Arguin, Mauritania, leave in short period; departure not correlated with tail winds (ground level or 5,000 m; Piersma et al. 1990). Body mass constant through winter; in Apr, gain about 35% 2–3 wk before departure (1–1.2%/day; Zwarts et al. 1990b). Birds increase foraging time (including during night) at highest food intake rates, and have higher metabolic rate, in Apr, when putting on premigratory fat (see Food Habits: metabolism and temperature regulation, below).