Measurements

See Appendix 2 . On average, females of N. p. hudsonicus have significantly longer bill, wing, tail, tarsus, and middle toe than males. Sex can be determined for about 73% of birds using a combination of bill, wing, and tail lengths (Skeel 1982). Female’s bill usually longer than mate’s bill: difference averaged 9.3 mm (range 2.9–17.9, n = 27 pairs) where female bill was longer; difference was 2.7 mm in 1 pair where male bill was longer (MAS; sex determined from discriminant score, see Skeel 1982). Breeding females significantly heavier than males. Proportion of bill length decurved (averaging 0.52) and number of degrees dropped (averaging 11.7, n = 78) does not differ between sexes (Mallory 1981). Juvenile wing and tarsus lengths do not differ significantly from adult. Adult bill length often not reached until first midwinter (Cramp and Simmons 1983). For Old World races, see Cramp and Simmons 1983 .

A comparison of eastern and western populations of N. p. hudsonicus yields no significant difference in bill length of females or males; however, wing length of both males and females is significantly longer in western than in eastern populations; tarsus length is similar in males, but significantly longer in western females (Appendix 3). In a comparison of skins, Taverner (1942) found no differences in plumage between eastern (n = 97) and western (n = 46) populations.

See Appendix 2 .