Avian response to shade-layer restoration in coffee plantations in Puerto Rico

Abstract

Documenting the evolving processes associated with habitat restoration and how long it takes to detect avian demographic responses is crucial to evaluate the success of restoration initiatives and to identify ways to improve their effectiveness. The importance of this endeavor prompted the U.S. Fish and Wildlife Service and the USDA Natural Resources Conservation Service to evaluate their sun-to-shade coffee restoration program in Puerto Rico initiated in 2003. We quantified the responses of 12 resident avian species using estimates of local occupancy and extinction probabilities based on surveys conducted in 2015–2017 at 65 restored farms grouped according to time-since-initial-restoration (TSIR): new (2011–2014), intermediate (2007–2010), and old (2003–2006). We also surveyed 40 forest sites, which served as reference sites. Vegetation complexity increased with TSIR, ranging between 35 and 40% forest cover in farms 6–9 years TSIR. Forest specialists (e.g. Loxigilla portoricencis) exhibited highest average occupancy in farms initially classified as intermediate (6–9 years) and old (>10 years), paralleling occupancy in secondary forests. Occupancy of open-habitat specialists (e.g. Tiaris olivaceus) was more variable, but higher in recently restored farms. Restoring the shade layer has the potential to heighten ecological services derived from forest specialists (e.g. frugivores) without losing the services of many open-habitat specialists (e.g. insectivores). Annual local extinction probability for forest specialists decreased with increasing habitat complexity, strengthening the potential value of shade restoration as a tool to enhance habitat for avifauna that evolved in forested landscapes.