The effect of weather conditions on the behavior of ospreys in northwestern Washington

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Abstract
In northwestern Washington, weather conditions have little or no effect on the behavior of breeding ospreys (Pandion haliaetus). When young are unfledged, the duration of hunting trips increases with increasingly gusty winds, but this accounts for only 8% of the variation in lengths of hunting trips. No weather conditions affect hunting trip length for adults with fledged young. Neither the rate of prey delivery by adults to offspring nor the size of prey is correlated with any weather variable measured in this study. Furthermore, both male and female ospreys spend large parts of each day perched at or near their nest throughout all stages of the nesting cycle, but weather has almost no effect on this behavior. These results are nearly identical with those from a Virginia study in which weather conditions were significantly different. Consequently, in contrast to other birds, neither the rate of food delivery nor, ultimately, osprey brood size appears to be limited by weather-mediated foraging success.