RELATIVE ABUNDANCE AND MICROHABITAT OF FOUR SYMPATRIC ANTPITTAS IN AN INTERANDEAN VALLEY OF SOUTHERN ECUADOR

Abstract

Exploring mechanisms that determine species coexistence is a key step to understand community organization and patterns of distribution of biodiversity. Anpittas, genus Grallaria, offer a great opportunity to measure coexistence mechanisms among closely related species. Antpittas are terrestrial insectivores with a specialized foraging technique and limited dispersal abilities; these factors could produce high levels of niche overlap and consequently reduce the chances of stable coexistence. We explored niche partitioning in space among four antpitta species (Rufous Antpitta, Chesnut-crowned Antpitta, Undulated Antpitta, Tawny Antpitta) which coexist in a tropical Andean valley located in southern Ecuador. We determined the abundance of each antpitta species in mature native forest, shrub, pasture, and páramo habitats, and gathered data about the microhabitat of each species. Abundance was determined using point counts, territories were located by triangulating on individual calls, and microhabitat characteristics were measured within each territory. We found no differences in the abundance or probability of occurrence of species among habitats for Rufous Antpitta, Chesnut-crowned Antpitta, and Undulated Anpitta, but Tawny Antpitta was restricted to páramo. At the microhabitat level, Rufous and Chesnut-crowned Antpittas shared similar vegetation characteristics, with the important presence of shrubs. Undulated Antpitta occurred in a microhabitat characterized by the presence of trees and a ground cover of mosses, while Tawny Antpitta occupied microhabitats with an open vegetation. In general our results suggest that closely related birds could partition their niche at different spatial scales, which could promote the coexistence of species in the tropical Andes.