Fruits in the Diets of Neotropical Migrant Birds in Costa Rica

Abstract

We used fecal samples collected from birds captured in mist nets to determine the occurrence of fruit in the diets of neotropical migrant birds (species that breed in North America and winter in Central and South America) at six study sites in Costa Rica. A total of 1016 migrants representing 30 species were captured. Fecal samples were collected from 85 percent of all birds captured. Fruits (seeds, pulp) occurred in 58 percent of all fecal samples; the proportion of fecal samples containing fruit ranged from 0 percent (9 species) to over 90 percent (9 species). Individual fecal samples contained seeds from as many as 4 species of plants. At least 98 plant species from at least 29 plant families were represented in fecal samples. Species of Melastomataceae accounted for 37 percent and those of Rubiaceae for 16 percent of all species recorded. Number of fruit species in diets of individual migrant species ranged from 0 (9 species) to 63 (Swainson's Thrush, Catharus ustulatus). Our data demonstrate that some migrants may rival permanent residents in the diversity of fruits they consume. A shift to increased frugivory in the late dry season, as birds were preparing to migrate north, was noted.