Microhabitat segregation, foraging behavior, and elevation enable coexistence of new world warblers (Aves: Parulidae) in agroforestry systems

The way in which closely related species segregate by habitat, and the mechanisms that allow their coexistence, are of interest in community ecology. When ranges of several species overlap (i.e., they are sympatric), those that use the same food resources should differ in other niche dimensions due to niche complementarity or resource partitioning. In bird communities, this primarily occurs through differences in foraging behavior, diet specialization or composition, and habitat use. In this paper, we evaluated how six species of new world warblers (Canada Warbler Cardellina canadensis, Tennessee Warbler Leiothlypis peregrina, Bay-breasted Warbler Setophaga castanea, Cerulean Warbler Setophaga cerulea, Blackburnian Warbler Setophaga fusca, and Tropical Parula Setophaga pitiayumi) segregate their ecological niches across an elevational gradient of agroforestry systems in the Western Andes of Colombia. We found evidence of microhabitat (vertical forest stratum use, foraging height and substrate) and elevational segregation for the six warbler species, suggesting patterns of multidimensional niche partitioning. High levels of niche overlap among microhabitat variables could indicate that interspecific interactions are key for structuring this co-occurring parulid community. In particular, the warblers exhibited a clear distributional pattern across the elevational gradient. Our analysis of multiple niche dimensions (i.e., elevational and microhabitat parameters) revealed differential patterns of habitat use that can suggest niche partitioning in ecologically similar species.