Sex-specific nestling growth in an obligate brood parasite: Common Cuckoo males grow larger than females

Abstract

ABSTRACT Growth is a key life history trait that is closely related to individual fitness. In altricial birds, growth is restricted to a relatively short period, and depends primarily on the amount or quality of food and hence on parental care. Obligate brood parasites do not care for their own offspring but impose this burden on other species (hosts). As many brood parasites exploit various host species, their progeny are expected to receive different levels of parental care. Parasite growth has thus often been explored in the context of host parenting abilities and only rarely with respect to its sex specificity. Here, we fill this gap in knowledge and explore sex differences in the growth of Common Cuckoo (Cuculus canorus) nestlings reared by 2 warbler hosts in the genus Acrocephalus. As adult Common Cuckoo males are 5–16% heavier than females, we assumed that nestlings would also differ in size and thus in growth performance. To test this assumption, we used a nonlinear mixed effects modeling approach...