A brood-size manipulation experiment with Peregrine Falcons, Falco peregrinus, near Canberra

Abstract

Brood sizes of Peregrine Falcons in south-eastern Australia were manipulated to examine the effects on parental foraging effort and offspring growth rate. In broods enlarged by one, nestling growth rates were not affected but parents responded by bringing larger prey species and more biomass than did parents of control or reduced broods. Prey size and biomass decreased for the reduced brood. We conclude that parents appeared to increase hunting efforts to meet greater demands for food, and decrease hunting efforts for the reduced brood, but that direct observation of hunting behaviour by colour-marked and radio-tagged Peregrine Falcons with enlarged, reduced, and natural broods is necessary to determine how parents respond.