Systematics

Bock (1958) stated that skull characters that had been used to differentiate the Black-bellied Plover (Squatarola) from the golden-plovers (Pluvialis) were incorrect or misinterpreted and argued, as did Drury (1961), that skull differences were attributable to differences in nasal glands, which in turn correspond to wintering habitats. Bock also rejected Black-bellied Plover’s small hind toe as generic character. Delacour and Mayr (1945) combined Squatarola with Pluvialis, a decision finally accepted by the American Ornithologists’ Union (1973). Hind toe more likely primitive than derived, so this species is probably a relatively primitive plover (hind toe also in 2 Charadrius and about half the Vanellus species).

Red-breasted Dotterel (Charadrius obscurus) of New Zealand combined with Pluvialis (Bock 1958), but this very different bird retained in Charadrius by subsequent authors. Pluvialis suggested as a recent arctic offshoot of Charadrius but without evidence (Jehl 1968).

Size variation clinal and relatively slight: largest in e. Siberia, smaller in w. Europe and Alaska, smallest in Canada (Cramp and Simmons 1983). Average wing length of breeding males 200.4 mm (n = 35) in ne. Siberia, 198 mm (n = 8) in Alaska, and 191.7 mm (n = 14) in Canada (Vaurie 1964). Tarsus length and bill depth best measurements to discriminate populations (Engelmoer et al. 1987). Alaska breeding birds weigh 10–20% more than those of Victoria I. (Appendix 2). Birds wintering in n. South America about one-fourth lighter in weight than those wintering in South Africa (Cramp and Simmons 1983), perhaps birds from breeding populations at extremes of size variation.

No subspecies recognized at present, although 2 previously named. P. s. cynosurae and P. s. australis of authors rejected by Manning et al. (1956). Perhaps considerable gene flow across breeding populations in this very vagile species.

Black-bellied Plover forms distinctive group with congeners (Greater Golden-Plover [P. apricaria], American Golden-Plover [P. dominica], and Pacific Golden-Plover [P. fulva]) but stands apart by larger size, vestigial hind toe, and paler coloration, perhaps all adaptations to marine habitat.