Measurements

General decrease in size from east (Hudson Bay) to west (Alaska); wing length averages 122.5 ± 3.22 SD in east, n = 32; 119.8 ± 2.91 SD in west, n = 33 (Prater et al. 1977); birds at Quill Lake, Sas-katchewan, have long wings (average 126.7 mm, n = 11) and sexual difference, so clinal variation may not be present (Hayman et al. 1986). Deserves further study.

Breeding females have slightly longer wings than males (p < 0.05), and males have slightly longer middle toes (p < 0.05) and culmens than females (p < 0.05; Teather and Nol 1997). Measurements of migrants in New Jersey were similar to those of breeding birds in Churchill, Manitoba (see Appendix).

Females are heavier and in general larger than males (Table 2; Teather and Nol 1997). Fat reserves are higher in Gulf of St. Lawrence autumn migrants than in individuals measured in Venezuela in spring (McNeil and Burton 1973). Migrants show higher mass in fall than in spring at Chincoteague National Wildlife Refuge, VA (see Table 2); in both seasons in most years, positive relationship between date weighed and mass, so later-arriving (or captured) birds heavier. In Churchill, Manitoba, no breeder heavier than 50 g (females) or 48 g (males; EN); weights of 50–73 g (the latter 146% of maximum breeding mass) are common in spring and fall migrants (see Table 2; N. Tsipoura pers. comm., EN using data from J. Spendelow unpubl.).