Measurements

Representative data summarized in Appendixes 1 and 2 . For additional linear measurements, see Sutton and Parmelee 1956, Van Tyne and Drury 1959, Blake 1977 (American Golden-Plover); Fay and Cade 1959, Saito and Walker 1972, Kinsky and Yaldwyn 1981, Dorogoy 1982, Marchant and Higgins 1993 (Pacific Golden-Plover); and Ridgway 1919, Bailey 1948, Vaurie 1964, and Hayman et al. 1986 (both species). For additional mass measurements, see Musacchia 1953, Van Tyne and Drury 1959, Johnston 1964 (American Golden-Plover on breeding grounds); and Johnston and McFarlane 1967, Saito and Walker 1972, Barter 1988, and Johnson et al. 1989 (Pacific Golden-Plover weight cycle through wintering season).

Past records of linear measurements (both species) and mass measurements (non-breeding Pacific Golden-Plover) showed no significant differences between the sexes (Saito and Walker 1972, Connors 1983, Cramp and Simmons 1983, Johnson et al. 1989, Marchant and Higgins 1993). A more recent study by Johnson and Johnson (2004) found slight but statistically significant differences in head, tarsus, bill lengths of Pacific Golden-Plovers, with females averaging smaller than males; however, differences were all < 1.0 mm and too small to be of any practical application. In the same study, linear measurements of American Golden-Plovers did not differ between the sexes. No difference in Pacific Golden-Plover between wing lengths of fall adults and juveniles (Johnson et al. 1989). However, this relationship changes during the ensuing months as gradual wear of retained Juvenal primaries shortens the wing considerably (>6 mm lost by time of Prebasic II molt; see Barter 1988); by spring the difference between the age groups becomes highly significant (Johnson and Johnson 2004). Thus, age structure of the sample is an important but often unknown or unreported variable in calculations of wing length means.

Based on museum specimens, wing lengths appear to vary on nesting grounds along a latitudinal cline, shortest in western Siberia, longest in Kamchatka and Alaska (see Byrkjedal and Thompson 1998). However, Johnson and Johnson (2004) found almost no statistical variation among wing length samples from living birds (a few freshly collected) at several sites from the Taimyr Peninsula to w. Alaska, all measured with the same technique (flattened and straightened primaries). By contrast, the wing length differential between two large samples from widely separated migratory corridors (Oahu on Mid-Pacific Flyway vs. Torey Depression on transcontinental Asian Flyway; sources 12 and 18, respectively, Appendix 2) is highly significant (P = 0.0001). These results (Oahu sample significantly longer-winged that Torey Depression sample) tend to support the foregoing cline as there is strong migratory connectivity between Oahu and Alaska whereas plovers stopping over in the Torey Depression are likely en route to Siberian breeding grounds. Clearly, the relationship between geography and wing length needs further study.

At arrival on breeding grounds, most birds are likely carrying fat reserves, but no precise measurements available. Limited and sometimes conflicting information on weight changes during subsequent weeks may reflect regional variations in food supplies and weather. For American Golden-Plover: birds sampled in n.-central Alaska from May to Jul showed downward trend of 4–9% in males, 10–15% in females (Irving 1960); at Barrow, females averaged 14% heavier than males during May and June (unpubl. data of F.A. Pitelka, see Connors 1983); at Churchill, limited data (Appendix 1) hint females are less stressed than males (P = 0.05), while birds on Seward Peninsula nesting grounds (Appendix 1) showed no significant weight difference between the sexes (P = 0.39). For Pacific Golden-Plover: a small sample from ne. Siberia collected Jun–early Jul averaged about 30 g less in males (n = 5) than in postlaying females (n = 2), suggesting that reproductive duties were more stressful on males (Kistchinski et al. 1983); the same trend (see Appendix 2) was evident among nesting Pacific Golden-Plovers on the Seward Peninsula (P <0.0001; OWJ) and on the nw. Taimyr Peninsula (P = 0.04, calculated from data in Schekkerman et al. 2004); but not in the n. Taimyr sample (P = 0.09, from data provided by P. Tomkovich).