Diet and Foraging Behavior of Vaux's Swifts in Northeastern Oregon

The diet of Vaux's Swifts (Chaetura vauxi) during the breeding season consisted primarily of insects in the orders Homoptera (hoppers, aphids, whiteflies), Diptera (flies), Ephemeroptera (mayflies), and Hymenoptera (ants, parasitic wasps). Diet was determined from 223 food boluses collected from adults feeding nestlings and represented 24,133 individual insects and spiders. Diet did not differ among five study areas or by time of day. A pair of swifts feeds an average of 5,344 arthropods to their nestlings each day, and an average of 154,976 arthropods during the nestling growth period. Radio-tagged swifts foraged up to 5.4 km from the nest. Of actual sightings of radio-tagged birds, 64% were foraging over land, 27% were foraging over water, and 9% were traveling in a straight line.