Body condition and molt chronology of waterfowl in east central Texas

Abstract

Waterfowl undergo changes in body condition during migratory and wintering periods that can affect survival and reproduction. Understanding how condition varies among age and sex cohorts and temporally can inform habitat management during the post- and pre-breeding period. We examined changes in body composition and molt of three waterfowl species migrating and wintering in managed moist-soil units in east central Texas and determined the influence of season, age, and sex using Analysis of Variance. We examined age, sex, and season effects on body condition indices (body mass divided by wing chord) using mixed-effects models and determined the influence of molt score on body condition using linear regression. For specimens collected from 2004–2007, we found differences in body composition among age and sex groups for Blue-winged Teal (Spatula discor), a migrant through this study area, and for Green-winged Teal (Anas crecca), and Northern Shoveler (Spatula clypeata), which are wintering species. We found a mid-winter decline in body condition for Green-winged Teal. Blue-winged Teal were in worse condition in spring than in fall, which could be due to differences in energy accumulation prior to departure to wintering grounds in fall and post-arrival in spring. We did not find an effect of season for Northern Shoveler. For all species, adults were in better condition than juveniles. Molt score was greatest in late-winter for all species combined (x̄ = 11.60, SE = 2.45). We did not find an effect of molt score on body condition for any species. Wintering waterfowl in east central Texas appear to be in good condition and did not show molt-induced stress during the migratory and wintering periods. Changes in condition among specimens and across seasons indicate that there should be consideration in the timing and quality of management in regional approaches to moist-soil management for migrating and wintering waterfowl.

Keywords

• body composition
• blue-winged teal
• condition indices
• feather molt
• green-winged teal
• molt intensity
• northern shoveler
• richland creek wildlife management area