LTREB: Linking Individual and Spatial Variation to Demography and Population Dynamics of a Neotropical Parrotlet

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

LTREB: Linking Individual and Spatial Variation to Demography and Population Dynamics of a Neotropical Parrot Steven R. Beissinger This long-term research project will continue studies of a South American parrot, the Green-rumped Parrotlet (Forpus passerinus), to address marked variation among individuals and across small distances in behavior, demography and population dynamics. Continued long-term studies, which have been conducted since in Venezuela since 1988, will link social system, dispersal and demography to population dynamics. Thirteen years of similar work has revealed a complex social system dominated by large numbers of nonbreeding males which occur in various social groupings, a low rate extra-pair fertilizations that are often assigned to males residing far from the nesting pair, and unusual spatial variation in the onset of breeding between two populations (upland and lowland) located only 500 m apart and differing in elevation by 1-2 meters. They have also found different patterns of population growth in the two populations that can be attributed to: (1) higher reproductive success in the upland population, (2) young females dispersing much farther than males, often leaving the study area altogether, and (3) young males dispersing from the poorer quality lowland habitat to the better quality upland habitat. Specific objectives of the study are to: (1) determine movement patterns and affiliations of breeders and nonbreeders, and dispersal of young to understand how they might account for extra-pair parentage patterns, small-scale variation in the onset of breeding, and differences among the sexes and populations; (2) document annual variation in the onset of breeding among populations of parrotlets that occurs at small spatial scales and measure food availability to see how this affects timing of laying; and (3) understand the effects of the individual and spatial differences in demography and population dynamics by developing population models that integrate behavior with sexual- and habitat-related differences in demography. Study goals will be accomplished by expanding the number of parrotlet populations under study; using radio-telemetry to track the daily movements and interactions of breeding pairs and nonbreeding males; and continuing behavioral, demographic and environmental monitoring to refine our understanding of the social system and to estimate vital rates.