Occupancy of the Sooty Ant-Tanager (Habia gutturalis) and White-Mantled Barbet (Capito hypoleucus) in fragmented forests of the Central Andes in Colombia

Abstract

The Sooty Ant-Tanager (Habia gutturalis) and White-Mantled Barbet (Capito hypoleucus) are endangered and endemic birds of Colombia. Both species have small geographic ranges and presumably low population sizes possibly due to habitat destruction and fragmentation. In order to estimate the effects of landscape features on the occupancy of both species, we sampled a variety of landscape configurations within the buffer zones of two hydroelectric impoundments in the Central Andes of Colombia and applied occupancy models to estimate the proportion of area occupied as a function of these covariates. We surveyed 35 point-counts in each hydroelectric impoundment, between June and July of 2014 and 2015. We used single-season models to estimate occupancy while recognizing imperfect detection. Mean occupancy estimates in the study area were similar for both species (0.61 SD=0.33 for the Sooty Ant-Tanager and 0.63 SD=0.25 for the White-Mantled). Nonetheless, occupancy probability within the study area was very different between them. The best model for the Sooty Ant-Tanager indicated a decrease in occupancy with elevation, whereas the top model for the White-Mantled Barbet indicated an increase in occupancy with distance from streams. Detection probabilities were similar for both species (>0.4) and declined significantly during the second year. Our results provide quantitative guidelines that can be used to evaluate and monitor the state of these populations on the short and long term.