Investigations of sexual dimorphism in live Kittlitz's Plover Charadrius pecuarius from inland South Africa

Abstract

Charadrius plovers generally show little sexual or seasonal dimorphism in size and coloration, but most published measurements come from museum specimens. We aimed to determine sexual size dimorphism in live Kittlitz's Plovers Charadrius pecuarius, based on measurements of 96 males and 112 females ringed at Barberspan Bird Sanctuary (North West province, South Africa) between February 2008 and October 2009 and sexed by DNA analysis. The females were significantly heavier than the males in September–October, but their mass decreased significantly from September to the end of March (b = −0.10, t = 3.82, P = 0.0002), likely because of egg laying. Body mass has limited utility for sexing, because heavy birds with high fat scores of both sexes, possibly itinerants, occurred in all months. Tarsus-and-toe length differed between sexes (P = 0.066). Wing length of birds with old primaries decreased in September–October (ANCOVA, F1,153 = 8.84, P = 0.003), but did not differ between the sexes (ANCOVA, F1,153 = 0.23, P = 0.626). Wing length for birds with fresh feathers, total head length, bill length, tarsus length and height of the white forehead patch did not differ between sexes. We attribute this lack of any clear sexual dimorphism to the species’ monogamous mating system and shared parental care, and to its simple terrestrial displays, which would likely result in weak intersexual selection.