Bioacoustic analyses reveal that bird communities recover with forest succession in tropical dry forests

With expanding anthropogenic disturbances to forests around the world, forest restoration is increasingly important for bird conservation. Restoration monitoring is critical for understanding how birds respond to forest regeneration and for assessing the effectiveness of restoration efforts. Using bioacoustic monitoring, we recorded bird communities during both dry and wet seasons at 62 sites along a chronosequence of tropical dry forests in the Area de Conservacion Guanacaste in Costa Rica. Tropical dry forests rank among the globe's most imperiled ecosystems, adding special urgency to their restoration and accompanying restoration monitoring. We found that bird species diversity, richness, and abundance increase with measures of forest maturity. Our results show that bird communities in regenerating areas become more similar to those of undisturbed areas as forests mature. This suggests that bird communities are recovering to predisturbed conditions in regenerating sites, and that maturing tropical dry forests are home to an increasingly diverse and abundant community of birds. We conducted an additional assessment, by sampling 30 locations using point-counts that were originally surveyed 23 years ago. We found that species richness and abundance were similar across this 23-year interval, although bird community composition changed because several forest-specialist species were only detected in the later period. Our research reveals that the regenerating tropical dry forests of northwestern Costa Rica have recovered species richness and abundance levels and are currently undergoing a succession in community composition toward that of a primary tropical dry forest. Our study shows bird communities recovering in a nearly century-old chronosequence of regenerating forests.