INFLUENCE OF WEATHER ON CONCLUSIONS ABOUT EFFECTS OF HUMAN ACTIVITIESON RAPTORS

Failure to account for abiotic factors in assessing human effect on ra ptor behavior can result in dubious conclusions because the same data can produce opposing management recommendations depending on use of we ather variables as covariates in analyses. We illustrate this problem with examples from a study of the potential effects of military traini ng on raptor behavior. Variation in weather explained more (P < 0.001) variation in raptor abundance than did military activity. Decreasing residual error, by controlling for weather variation in analyses, reve rsed conclusions drawn from 2 of 4 tests of military influence on rapt or abundance. Pooling data reduced the need for controlling weather fa ctors by increasing test power to detect small differences, but sacrif iced the ability to detect temporal effects of training, which might b e useful to managers. Blocking data by season and time of day did not control for variation in weather; when weather factors were included a s covariates, conclusions were reversed in 2 of 9 temporal/seasonal bl ocks in each of 2 analyses testing the effect of military training on prairie falcon (Falco mexicanus) occurrence. Weather data obtained at the study site during observations explained more (P = 0.009) variatio n in raptor abundance than did data obtained from the National Weather Service. However, selecting weather data from either source resulted in similar management conclusions. Researchers must address environmen tal factors that are likely to influence animal behavior but that cann ot be removed from the study design.