Tropical agriculture is a major driver of biodiversity loss, yet it can provide conservation opportunities, especially where protected areas are inadequate. As agricultural lands rapidly expand in the tropics, they become critical for the future of tropical biodiversity, but little is known about their long-term conservation value. To investigate the long-term biodiversity capacity of agricultural countryside, we quantified bird population trends and changes in community composition in southern Costa Rica by systematically mist netting and banding 57,255 birds of 265 species between 1999 and 2010 in shaded and sun coffee plantations, riparian corridors, secondary forests, forest fragments, and primary forest reserves. Combining bird mark-recapture data with a global bird trait database, we measured the abundance and diversity of birds, quantified the composition and changes in bird communities, constructed habitat and diet functional signatures of the bird community of each habitat type, and used mark-recapture analyses to estimate the rates of realized population growth (λ) for 112 populations at 19 sites representing seven habitat types.
Results/Conclusions
We recorded 185 bird species in coffee plantations and 230 species at forest sites, but more bird populations (69) were declining than were stable (39) or increasing (4). Declines were common in resident, insectivorous, and more specialized species. There was no relationship between the species richness of a habitat and its conservation value. High-value forest bird communities were characterized by their distinct species composition and habitat and dietary functional signatures. While 49% of bird species preferred forest to coffee, 39% preferred coffee to forest and 12% used both habitats, indicating that coffee plantations have some conservation value. Coffee plantations, although lacking most of the forest specialists, hosted 185 bird species, had the highest capture rates, and supported increasing numbers of some forest species. Coffee plantations with higher tree cover (7%vs13%) had more species with increasing capture rates, twice as many forest specialists, and half as many nonforest species. Costa Rican countryside habitats, especially those with greater tree cover, host many bird species and are critical for connecting bird populations in forest remnants. Diversified agricultural landscapes can enhance the biodiversity capacity of tropical countryside, but, for the long-term persistence of all forest bird species, large (>1,000 ha) protected areas are essential.