Cuckoo for Cricket Puffs: A Detailed Analysis of Early Nestling Diet for the Greater Ani (Crotophaga major)

Abstract

The nestling period is a critical time for bird survival and fitness. Communal breeders like the Greater Ani (Crotophaga major) can divide nestling care (feeding, protection, etc.) among multiple individuals, increasing the likelihood of nestling survival. For this species, nestlings develop fast and explore outside of the nest only five days after hatching meaning a sufficient diet is especially crucial during this time. This thesis categorizes the early diet of Greater Ani nestlings from 12 groups around Gatún Lake and Barro Colorado Island in Panama. I found that offspring are provided a wide variety of arthropods, insects, and vertebrates. Orthopteran species – katydids, crickets, grasshoppers—and spiders made up most of the prey items. Large lizards and frogs also appear in nestling diet. Throughout the early nestling period, most prey items are larger in size, presumably for increased nutrition. For one nest group, prey size increased over time showing that nestling diet may change in proportion to nestling growth. Finally, whether nests reside on mainland shores versus an island has no significant effect on nestling diet in terms of prey type and proportions. These results provide the most detailed characterization of Greater Ani nestling diet to date and may serve as the initiation of further studies of Greater Ani nestling diet.