Differential Avian Responses to Coffee Farming Lead to Community Homogenization in a Working Landscape in Jardin, Colombia.

Abstract

In Colombia, coffee production has an ingrained cultural and economic importance. Coffee is cultivated in biodiverse areas using a variety of practices ranging from sun-exposed monocultures to mixed and shaded plantations. Management practices on this working landscape alter the composition of bird communities. We hypothesize that coffee agroecosystems homogenize bird communities by favoring the occupancy of non-forest dependent bird species and deterring forest dependent birds. We evaluate the effects of coffee plantations and associated metrics of vegetation structure on a subset of bird species in an agroforestry landscape in the Western Andes in Colombia and evaluate the hypothesis of community homogenization. We collected data in two consecutive years in 153 sites in coffee plantations and other habitats in Jardin, Colombia. In order to evaluate birds response to changes in the working landscape we made single-season occupancy models and used five covariates: coffee (binary covariate), foliage height diversity (FHD) and canopy height (CH) as proxies for coffee management practices, human footprint (LHFI), and elevation. Finally, we used generalized dissimilarity models (GDM) with the same covariates and geographical distance to evaluate the homogenization hypothesis among coffee sites. We identified 193 species (six endangered and five endemics) and modeled occupancy of 74 species. Coffee plantations significantly decreased the occupancy of 14 species while 13 were favored. In general, non-forest dependent species preferred lower FHD and lower CH values, and occurred at lower elevations with high LHFI. On the contrary, forest dependent species preferred higher FHD and CH, and were found at higher elevations. The GDM with best fit supported the hypothesis that coffee sites tend to be more similar than no-coffee sites, and that elevation and FHD explained most of the variation in dissimilarity. The working landscape in Jardin holds an important community of birds but coffee plantations are driving its homogenization. We anticipate that non-forest dependent birds will continue to colonize working landscapes, unless structural vegetation changes are promoted. Increasing FHD and CH is a potential strategy to improve forest dependent bird occupancy and reduce homogenization in Jardin.