Nonrepresentative Sampling during Waterfowl Banding: Emphasis on Body Condition

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Abstract
We trapped mallards (Anas platyrhynchos) at 3 sites on the eastern shore of Lake St. Clair, Ontario, during August and September of 1989 and 1990 to investigate the potential for nonrepresentative sampling in typical autumn (i.e., pre-hunting season) duck-banding operations. Intersite comparisons showed that the local population was spatially segregated with respect to sex, age, molt chronology, and body condition, indicating a potential danger when the spatial distribution of the banding effort is limited. Sex composition of trapped samples varied according to size of the daily catch; smaller catches contained proportionally more females. However, size of the catch had no apparent influence on age ratios. Analyses conducted separately by sex and age provided little evidence for a relationship between size of the catch and condition of captured individuals. These results are generally inconsistent with the hypothesis that food-stressed individuals are among the first to respond to baited areas and enter traps. Thus, condition-related trap selectivity is unlikely to vary with size of the trapped sample, as some authors have suggested. Additional research is needed to determine whether bait-trapped samples of ducks are generally skewed toward individuals in poor condition.

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