Migration

West Indies populations resident; other populations short-, medium-, or long-distant migrants to coastal areas of the Americas: on Pacific side from California to central Chile and on Atlantic side (including Gulf of Mexico) from s. U.S. to Brazil. Those breeding in Canadian Maritimes probably long-distance, transoceanic migrants (Bent 1929). Migrants observed primarily along coasts and irregularly throughout interior U.S. Spring migration more rapid than fall migration. Fall migration begins in Jun, about as early as that of any North American sandpiper. Many oversummer on the wintering grounds.

Spring

Western. Latest specimen identified as inornatus for Florida collected 18 May (Stevenson and Anderson 1993). Migration occurs late Mar through late May in Costa Rica (Stiles and Skutch 1989), early Apr–mid-May along lower Colorado River of s. Arizona and s. California, with most occurring there during brief 2-wk period peaking in late Apr (Rosenberg et al. 1991), and mid-Apr–early Jun along Oregon coast (Gilligan et al. 1994). Along California coast (San Francisco Bay), mean departure date among tagged wintering birds 6 Apr (range ± 9 d, n = 18; Kelly and Cogswell 1979). Farther inland, migration recorded 7 Apr–11 Jun in Kansas (Thompson and Ely 1989), and mid-Apr–mid-May, peaking in early May in Minnesota, with extreme dates of 21 Mar and 1 Jun in south and 26 Apr and 24 Jun in north (Janssen 1987).

Within breeding range, earliest arrival Malheur National Wildlife Refuge (NWR; Malheur Co.), OR, 21 Mar, with peak arrival 15–30 Apr (Littlefield 1990). In N. Dakota, median arrival date 22 Apr (range 18 Apr–5 May; Higgins et al. 1979). In Alberta, median arrival date 2 May (range 24 Apr–5 May, n = 9 yr; Sadler and Myres 1976).

Eastern. Migration occurs Mar–mid-Apr in Venezuela (Rompré and McNeil 1994). Within breeding range, arrives at Wallops I., VA, during first 2 wk of Apr, and largest influx there occurs during third week of Apr but occasionally arrives earlier; e.g., 34 arrived 1 Feb 1983 (Vaughn 1993). Arrives 25 Apr–15 May in Maryland (Stewart and Robbins 1958). Arrives during third week of Apr in Cape May, NJ, and migration continues steadily (no peak apparent) through May (Sibley 1997). In Massachusetts, earliest record 19 Mar; most spring maximum records during last week of Apr (Veit and Petersen 1993). Earliest Nova Scotia record 1 May (Tufts 1925).

Fall

Western. Breeders begin departing e. Oregon during latter half of Jun; very scarce by early Sep (Gilligan et al. 1994).

Outside of breeding range, migration recorded early Aug–late Sep in Minnesota, with no real peak in numbers; extreme dates of 20 Jul and 19 Oct in north and 25 Jul and 11 Oct in south (Janssen 1987); 1 Aug–24 Oct in Kansas (Thompson and Ely 1989); mid-Jul–Oct along Oregon coast; mid-Jun–mid-Oct in California (mainly coast), with largest influx late Jul–early Sep (Small 1994, Shuford et al. 1998); and mid-Jun through Aug or early Sep, with 2 records in Oct along lower Colorado River of s. Arizona and s. California (Rosenberg et al. 1991). Along California coast (San Francisco Bay), mean arrival date among tagged birds 1 Aug (range ± 47 d, n = 27; Kelly and Cogswell 1979). In Massachusetts, where fall specimens of inornatus outnumber semipalmatus by 33–6, migration peaks during last 2 wk of Aug, and species rare after Sep (Veit and Petersen 1993). At Cape May, NJ, Willets identified as inornatus average 10/fall, but few observers identify these individuals to subspecies there; earliest fall record 4 Jul, with earliest juvenile 29 Jul; western birds peak Aug–Sep, and most Willets observed Sep through winter are believed to be western birds (Sibley 1997). Earliest specimens identified as inornatus for Florida is 10 Aug (Stevenson and Anderson 1994).

Eastern. Latest Nova Scotia record 10 Sep (Tufts 1925). At Cape May, NJ, apparent migrants observed as early as 25 Jun, with up to 220 observed flying south over Delaware Bay on 3 Jul 1995; practically all adult breeders and most juveniles gone by 20 Jul (Sibley 1997). In Florida, where records of fall migrants may pertain to either subspecies, large influxes occur annually in coastal areas during Jul, and inland reports of migrants have also been recorded by second week in Jul; migration over-all may continue through Oct (Stevenson and Anderson 1994). In Bermuda, flocks observed passing overhead (Nonesuch I.) each summer in mid-Jul (D. Wingate pers. comm.); fall records range from early Jul to 25 Sep, with most occurring Jul–late Aug (Amos 1991). In ne. Venezuela, arrives 20–25 Jul, peaking late Oct–end of Nov (McNeil 1970, Rompré and McNeil 1994).

Routes

Western Willets migrate northward through Mississippi Valley in Apr, and those wintering on Carolina and s. Atlantic coasts may join this route by overland flight (Bent 1929). Migrant flocks observed casually across interior U.S. (e.g., Huntington, WV; Argabrite 1988). Migration west of Rockies occurs north along Pacific Coast and (less commonly) northward through interior valleys of California and Oregon to breeding grounds in w. U.S. and Canada (Bent 1929, Kelly and Cogswell 1979, Paulson 1993), although migrants regularly occur along lower Colorado River (Rosenberg et al. 1991). Very rarely recorded in interior British Columbia or n. Idaho (Paulson 1993). Band recoveries from banding programs in w. Canada included recoveries from Missouri (1), California (1), Mexico (5), and Costa Rica (1; Wilcox 1980, CLG-T). One juvenile banded in Saskatchewan seen 2.5 wk later at Galveston I., TX (Alexander and Gratto-Trevor 1997). Great Basin birds appear to spend winters along California coast, particularly San Francisco Bay area; much larger proportion of Willets marked in U.S. Great Basin observed in California, than those marked in Canadian Prairies (S. Haig and L. Oring pers. comm.; CLG-T). Western birds (exact breeding locations unknown) migrate to Atlantic Coast each fall, and fall/winter speci-mens outnumber Eastern birds in some areas (e.g., Massachusetts and Florida; Veit and Petersen 1993, Stevenson and Anderson 1994). Western birds apparently migrate back to breeding areas more directly and are rarely observed along ne. Atlantic Coast in spring (e.g., Cape May, NJ, and Massachusetts; Veit and Petersen 1993, Sibley 1997).

Eastern Willets migrate primarily over coastal and oceanic routes. Several arguments for trans-oceanic route from n. South America over Bermuda to Maritimes presented by Douglas (1996). Young banded in Georgia recovered in French Guiana; adult banded in Alabama recovered in Guyana (Wilcox 1980); chick banded on Wallops I., VA, in May recovered in Tobago in Aug (ffrench 1991).

Oversummering

Species oversummers throughout winter range in California (Small 1994); Middle America (Ridgely and Gwynne 1989, Stiles and Skutch 1989, Howell and Webb 1995), including Baja California (Carmona and Danemann 1998); West Indies (Raffaele et al. 1998); n. South America (ffrench 1991, Haverschmidt and Mees 1994); and possibly elsewhere. Western Willets that remain oversummer on Pacific Coast are social (Mendenhall 1970). On coastal Venezuela, Eastern and Western willets recorded through winter (McNeil 1970); summer counts only about 40% of maximum winter count (McNeil 1970, McNeil et al. 1990).

Migrates at night; generally observed in small flocks during migration (Tomkins 1965). No apparent difference in schedule of spring migration between sexes (Howe 1982, CLG-T). Adults depart breeding grounds before juveniles (Bent 1929); females depart prior to males (Howe 1982, CLG-T).

Little information. Spring migration associated with growth in testes and postbreeding migration associated with shrinking of testes (Tomkins 1965).