Impact of Habitat Heterogeneity and Structural Complexity on Nesting Success

Abstract

Agricultural intensification has been driving declines in avian biodiversity across the globe, however, research has shown that human-managed agriculture lands can provide habitat and resources to avifauna in addition to supporting sustainable avian populations. Coffee agroforestry has been spotlighted as an agroecological system that supports the abundance and richness of avifauna, though there is limited research on whether these systems support breeding populations and how management decisions impact avian nest success. This study seeks to fill gaps in the literature by comparing avian reproducible success in a shaded coffee farm and a neighboring sun-grown coffee farm. It investigates whether differences in habitat heterogeneity impact nesting success by measuring canopy cover, and vertical structure, and constructing a complexity index. It was hypothesized that the less intensely managed shaded coffee agroforestry system would have a higher probability of daily nest success than the more intensely managed sun-grown coffee. Results from this study found that nests in the agroforestry system (n=25) had a 5% higher daily nest survival rate than nests found in the sun-grown coffee system (n=18). Additionally, results suggest a negative correlation between vertical structure surrounding the nest and the success of nests, implying a trade-off between nest concealment and risk of failure.