Relationship of Body Condition to Survival of Mallards in San Luis Valley, Colorado

Abstract

Because body condition can influence survival probabilities in waterfowl, our objective was to determine if winter body condition was related to survival of mallards (Anas platyrhynchos). We obtained body mass and condition indices from mallards captured in southern Colorado from December through March 1986-87, 1987-88, and 1988-89. We collected waterfowl carcasses and wings from January through April 1987-89. In 1987, 1988, and 1989, we recovered 229, 4,193, and 1,663 mallard carcasses, respectively. Avian cholera (Pasteurella multocida), a source of mortality in all years, was prevalent in 1988. Starvation (ulna lipid levels <5%) was more prevalent (P < 0.01) among banded mallards than among unbanded mallards. We used logistic regression to assess relationships between condition at time of banding and whether a bird was found dead within 4 months after capture, shot by hunters the subsequent fall, recaptured 1 year later, or of unknown fate. In 1987, there was a relationship between recaptures and condition (P = 0.03), but no relationship between other status categories and condition. There were no relationships between status and condition in 1988. In 1989, only band recoveries from birds found dead were available for analysis; there was no relationship between condition at banding and whether a bird was found dead (P = 0.19). Waterfowl susceptibility to avian cholera may be unrelated to body condition; therefore, avian cholera mortality may have masked relationships among other mortality causes and condition. J. WILDL. MANAGE. 58(4):787-793