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Three ‐Speed Foraging During the Breeding Cycle of Yellow‐Rumped Caciques (Icterinae: Cacicus Cela)

Robinson, Scott K.
Ecology 1986 v.67 no.2 pp. 394-405
Lepidoptera, Orthoptera, breeding, energy intake, females, foraging, forest canopy, insects, larvae, microhabitats, nests, predators, understory, Peru
The foraging behavior of a color—marked population of the polgynous, colonial Yellow—rumped Cacique, Cacicus cela (Icterinae), was studied throughout the breeding cycle in southeastern Peru. Females changed their foraging rates and microhabitat use at each stage of the nest cycle, apparently in response to changes in protein needs, travel costs, and time constraints. Nonnesting females, with few such constraints, searched for insects slowly and inconspicuously high in the forest canopy where they caught prey (mostly small larval lepidopterans) at a low rate. When protein needs were high (i.e., during egg—laying and fledgling—feeding) or foraging time was restricted (i.e., during incubation), females accelerated their searching rates in all microhabitats. During the nestling—feeding period, when both protein needs and travel costs to and from the nest were high, females searched at the fastest rate and foraged more in the forest understory where they caught relatively more large orthopterans. These data suggest that females with few constraints minimize their exposure to predators, while energetically constrained females maximize their rate of energy intake.