THE DIET OF THE APLOMADO FALCON (FALCO FEMORALIS)IN EASTERN MEXICO

describe here breeding season diets of Aplomado Falcons (F&co femoralis) at 18 sites in Veracruz, Campeche, and Chiapas, Mexico, based on 256 animals in prey remains and 234 prey that I detected while watching the falcons’ feeding behavior. Birds comprised 94% of individuals in prey remains, but only 35% of prey that I saw being taken. Although the remainder and majority of the prey that I saw being taken were insects, 97% of prey biomass in this sample was birds. Common prey were moths, beetles, doves, cuckoos, and grackles. Prey animals ranged in weight from less than 1 g to over 500 g. Avian prey that I saw being taken averaged 67 g. In at least one case, prey size may have influenced prey selection within species since the falcons preferentially took female Greattailed Grackles (Quiscalus mexicanus), which are smaller than males. The swiftness of Aplomado Falcons in flight, coupled with their agility on foot and tendency to hunt cooperatively, may account for their broad prey preferences. They do not, however, capture swifts and swallows. The high proportion of birds in the diet may explain the falcon’s heavy contamination with residues of DDT.

DEAN P. HECTOR, The Condor 87:336-342