Variation in male provisioning in relation to brood size of Peregrine Falcons Falco peregrinus

Among large falcons males provide most of the prey for the breeding attempt. In the light of such high male contribution it might be expected that males vary in their provisioning ability and hence their reproductive success. Parental provisioning rates during the nestling period were investigated at thirteen Peregrine Falcon nests with broods of from one to four. For the entire nestling period of up to 50 days males contributed 85% of prey items and 71% of prey biomass delivered to nestlings. During the main period of nestling growth (< 30 days, by the end of which the nestlings had more or less reached full body weight) the males provided 93% of prey items and 86% of estimated prey biomass. Male provisioning rate was positively correlated to brood size and fledging success, but that of females was unrelated to brood size, fledging success or male delivery rate. In the first 29 days, males with a brood of three or four provided up to three times the prey deliveries and twice the biomass of males with a brood of one or two. Larger broods were fed more regularly than were smaller broods, and were fed at peak rate longer into the nestling period. In two broods of three, prey deliveries were less regular than to the other broods of three and in each a chick died. Females paired with a better provider appeared not to benefit directly through a decrease-in their own hunting effort, but it is proposed that they were advantaged through greater reproductive success. It is suggested that intrasexual variation in male provisioning ability may be less for highly dimorphic species, such as Peregrine Falcons, than for less dimorphic raptors, such as Australian Kestrels.