Lunar Influence on Foraging and Nesting Activity of Common Poorwills (Phalaenoptilus nuttallii)

Abstract

Whip-poor-wills (Caprimulgus vociferus) forage by sallying from a perch, are actived uring periods of the night with moonlight, and synchronize hatching with the lunar cycle.I n contrast, Common Nighthawks (Chordeiles minor) forage during continuous flight and do not increase activity during moonlit periods or synchronize their breeding activities with the lunar cycle. We used data on the foraging activity and nest timing of the Common Poorwill (Phalaenoptilus nuttallii) to test the hypothesis that moonlight influences the activity patterns and nest timing of this sallying caprimulgid. If foraging strategy alone influences the response to the lunar cycle, activity by Common Poorwills should be correlated with lunar light levels and hatching should be synchronized with the lunar cycle. Our results support the general prediction that lunar light allows poorwills to forage during periods of the night. However, contrary to expectations, increased foraging activity was correlated only with increasing moon height and not the percent of the moon face illuminated. Furthermore, the nesting cycle was not synchronized with the lunar cycle. We conclude that knowledge of foraging style alone is not sufficient to predict the nature of lunarphilia by goatsuckers. We suggest that habitat choice, duration of twilight, the number of breeding attempts, and the physiological ability to enter torpor also may be important factors mediating lunar influence on foraging activity.