Nest density and success of columbids in Puerto Rico

Abstract

A total of 868 active nests of eight species of pigeons and doves (columbids) were found in 210 0.1 ha strip-transects sampled in the three major life zones of Puerto Rico from February 1987 to June 1992. The columbids had a peak in nest density in May and June, with a decline during the July to October flocking period, and an increase from November to April. Predation accounted for 81% of the nest losses observed from 1989 to 1992. Nest cover was the most important microhabitat variable accounting for nest failure or success according to univariate and multivariate comparisons. The daily survival rate estimates of nests constructed on epiphytes were significantly higher than those of nests constructed on the bare branches of trees. Rainfall of the first six months of the year during the study accounted for 67% and 71% of the variability associated with the nest density estimates of the columbids during the reproductive peak in the xerophytic forest of Guánica and dry coastal forest of Cabo Rojo, but only 9% of the variability of the nest density estimates of the columbids in the moist montane second-growth forest patches of Cidra. In 1988, the abundance of fruits of key tree species (nine species combined) was positively correlated with the seasonal changes in nest density of the columbids in the strip-transects of Cayey and Cidra. Pairwise density correlations among the columbids suggested parallel responses of nesting populations to similar or covarying resources in the life zones of Puerto Rico.