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DIET AND NUTRITION OF NORTHERN PINTAILS WINTERING ALONG THE SOUTHERN COAST OF TEXAS

Abstract Most northern pintails (Anas acuta; hereafter pintails) in the Central Flyway winter within the Gulf Coast and adjacent rice prairies of Texas, USA. However, wintering habitat has declined in this region as a result of decreased rice production and changes in land use. Because pintails exhibit high winter site fidelity, more pintails are likely to rely on adjacent coastal habitats during winter as freshwater habitats along the Texas coast disappear. However, few studies have investigated the diet of pintails in estuarine environments. We estimated the composition and quality of the diet of pintails wintering along the lower Texas coast, and we compared our estimates to those for pintails in freshwater habitats. Proximate composition and true metabolizable energy (TME) were estimated for 4 foods in the diet of 253 pintails collected along the lower Texas coast during October–February 1997–1998 and 1998–1999. Shoalgrass (Halodule wrightii) rhizomes, wigeongrass (Ruppia maritima) seeds, dwarf surf clams (Mulinia lateralis), marine gastropods, and Gammarus amphipods comprised most of the pintail diet. Pintail diets in coastal habitats contained smaller proportions of protein and fat and a large proportion of ash compared to diets of pintails from freshwater habitats. As a result, the diet of pintails wintering along the lower Texas coast provided about half the TME of diets of pintails wintering in freshwater habitats. Because pintails rely on endogenous reserves acquired during winter and spring migration to support egg production, pintails wintering in Texas may experience greater reductions in recruitment and survival if displaced to coastal habitats.