DIET OF COMMON NIGHTHAWKS (CHORDEILES MINOR, CAPRIMULGIDAE) RELATIVE TO PREY ABUNDANCE

Optimal foraging theory predicts that when prey density is low, predat ors should employ a generalist feeding strategy and take prey in propo rtion to their abundance. The purpose of this study was to compare the diet of common nighthawks (Chordeiles minor: Caprimulgidae) with a me asure of prey abundance. Relative to the proportion of insects availab le, nighthawks consumed Coleoptera and Hymenoptera more than expected while Diptera were avoided. Only Trichoptera and Lepidoptera were cons umed in proportion to their abundance. A qualitative comparison of our results with data on nighthawk diets from the Okanagan Valley, Britis h Columbia, suggests that the birds in the two locations have differen t diets but similar preferences relative to the abundance of different insect orders.