Factors Affecting Body Condition of Northern Pintails Wintering in the Playa Lakes Region

Abstract

We assessed the effects of capture period, capture subregion, age, sex and habitat conditions on the body condition of migrating and wintering Northern Pintails (Anas acuta) in the Playa Lakes Region (PLR) of northwestern Texas. Body condition varied with sex, age, subregion and month during the wet 2002. During 2002, after-hatch-year (AHY) males had more carcass fat (g and percent) than did AHY females. Likewise, AHY males had 34% more carcass fat (g) than hatch-year (HY) males, but we did not detect differences between AHY and HY females. The average increase in carcass fat (g) from October to November-December during wet 2002, was 26% for males and 42 to 93% (HY) for females. Body condition of pintails in the south exceeded those captured in northern subregions of the PLR during wet 2002, but not dry 2003. Southern caught AHY males had 31% more carcass fat (g) than northern caught AHY males, but we found no differences for HY males. Females caught in southern subregions also had 24–77% more carcass fat (g) than northern captured females. During dry 2003, pintail carcass fat (g and %) did not vary by capture location or among age and sex classes, except for males, which increased carcass fat by 34% between capture periods. From our findings, we recommend that managers periodically assess pintail body condition to detect temporal trends of condition status and measure population response to conservation efforts. However, use of body condition measures to evaluate habitat management and conservation efforts must be evaluated in the context of habitat conditions, sample locations, period of sample collection and age and sex classes.