Measurements

See Table 2 . Field sexing was based in part on behavior and the data may include some misclassifications. Nevertheless, males significantly larger than females in culmen length, head length, and wing length (Table 2; Craik 1999); also bill width and bill depth (Coulter 1986). For data on tail fork, see Cramp 1985 and Olsen and Larsson 1995 . Data on tarsus length inconsistent: Cramp (1985) reported means of 20.2 mm ± 0.8 SD for males (n = 45), 19.8 mm ± 0.5 SD for females (n = 36); Olsen and Larsson (1995) reported means of 19.6 mm for adult males (n = 199), 19.4 mm for adult females (n = 111), 19.3 mm for juveniles (n = 152); Coulter (1986) reported means of 24.0 mm ± 0.8 SD for adult males (n = 50), 24.1 mm± 0.9 SD for adult females (n = 55); Erwin et al. (1986) reported mean of 22.8 mm ± 0.2 SD for unsexed birds in winter (n = 55).

See Table 2 . Means for breeding birds at Great Gull I., NY: 116 g ± 11 SD (n = 56; LeCroy and LeCroy 1974); 120 g (range 103–145, n = 56; LeCroy and Collins 1972). Means for wintering birds in Trinidad, Jan–Mar, 102.6 g ± 9.9 SD (n = 54; Blokpoel et al. 1984), and 102.2 g ± 8.3 SD (n = 89; Erwin et al. 1986); some of these birds were in poor physical condition (Blokpoel et al. 1984). For detailed studies of variations in mass within and among individuals and groups of breeding birds in Germany, see Wendeln and Becker 1996, 1999b; Wendeln 1997a, 1997b; Wendeln et al. 1997 . Birds collected in Germany in Sep weighed up to 156 g (Peters 1933). Birds trapped in Brazil in late Apr–early May weighed up to 200 g (Harrington et al. 1986).