Breeding ecology of shorebirds in the Playa Lakes Region of Texas

The Playa Lakes Region of Texas (PLR) is important for migrating shorebirds. This is the first study to examine habitat use, nest site selection, and breeding biology of shorebirds nesting in the PLR. Further, this is the first study to examine sex ratio manipulation, sexual dimorphism, and the appearance of a second adult male phenotype in a uniquely marked population of snowy plovers.;American avocets (Recurvirostra americana), black-necked stilts (Himantopus mexicanus), killdeer (Charadrius vociferus), and snowy plovers (Charadrius alexandrinus) nested in playas, saline lakes and riparian wetlands. In 1998 and 1999, 478 shorebird nests were monitored, of which 298 were snowy plover nests. Nests were initiated in May through late June--early July and nest success varied (P 0.05) between used (i.e., shorebirds nesting) and non-used (i.e., shorebirds not nesting) playas or riparian wetlands. Used saline lakes had more (P < 0.001) water, mudflats, and mudflats with vegetation than non-used saline lakes. All species preferred (P < 0.001) placing nests in areas with bare-dry ground or dry ground with vegetation.;During 1999 and 2000, 339 snowy plovers were captured. Using plumage assigned gender, adult sex ratios were generally biased (P < 0.05) but using PCR-based gender identifications, sex ratios generally did not deviate from unity (P > 0.05). Brood sex ratios were not biased, irrespective of nest initiation dates (P > 0.05). Adult snowy plovers exhibit sexual dimorphism in morphology and plumage ( P < 0.001), where females were generally heavier than males which were larger (P < 0.001) than females for other morphological measures. Males had forehead patches that were larger in area and longer in perimeter (P < 0.001) than females. A second adult male phenotype was characterized using both morphological measures and plumage characters.;This study demonstrated the importance of the PLR of Texas for breeding shorebirds, particularly snowy plovers. Similarly, conservation of saline lakes and playas will be prime management concerns in the future. The selective pressures allowing for the existence of a second adult male snowy plover phenotype is discussed.