Predation on Mexican free-tailed bats by Peregrine Falcons and Red-tailed Hawks

We observed Red-tailed Hawks (Buteo jamaicensis) and Peregrine Falcons (Fal co peregrinus) hunting Mexican free-tailed bats (Tadarida brasiliensis) dur ing their evening emergence and dawn return at Frio Cave, Uvalde County, Te xas in the summer of 1997. Predation by Red-tailed Hawks occurred primarily in the evening (89.5%), and predation by Peregrine Falcons was mostly at d awn (90.5%). In the evening, hawks appeared when large numbers of bats emer ged and they attacked at distances >50 m and heights <50 m above the cave. Termination of hunting by hawks in the evening coincided with sunset. In co ntrast, peregrines hunted for a longer period at dawn when bats returned bo th in high and low numbers, mostly <100 m of the cave but at various height s. Both species made higher proportions of flights passing by bats without attacking them at dawn (88.9% Red-tailed Hawk and 26.5% Peregrine Falcon) t han in the evening (16.4% Red-tailed Hawk and 0% Peregrine Falcon). Hawks h ad a higher attack rate and capture rate in the evening than at dawn and, i n the evening, hawks had a higher attack rate and capture rate, and caught a higher mean number of bats than hawks. Both species were more successful in catching bats after juvenile bats became volant and began foraging. In t otal, these raptors took 237 bats (96 Red-tailed Hawk and 141 Peregrine Fal con). We estimated the total number of bats taken between mid-April to mid- October to be about 2153 bats which could have accounted for <0.002% of the total colony.