Bird diversity along a gradient of tropical forest loss due to agriculture in central Veracruz, Mexico

Tropical ecosystems have undergone severe changes due to human activities such as land-use change for agriculture. However, in agricultural landscapes with remnants of native vegetation, high bird diversity may persist. Here we evaluated bird species richness, diversity, and composition in four landscape units with different matrices: cattle pastures, cornfields, mixed mosaics, and continuous forest. Using nets and direct observations, we recorded 138 bird species. We expected species richness to have a negative relationship with agricultural coverage, thus decreasing in the following sequence of landscape matrices: forest > mixed > corn > pasture. On the contrary, standardized species richness decreased from 122 to 93 species in the following sequence: pasture > mixed > forest > corn. Using a PERMANOVA, we detected significant changes in species composition among landscape units. These differences were represented in a NMDS plot and a Venn Diagram. Species diversity (Hill Numbers) also changed seasonally, and the forest unit had low richness but the highest evenness. This complex landscape allowed the presence of diverse species under risk categories. We conclude that despite recurrent human disturbances in this tropical region, the agricultural landscape, mixed with remnants of natural vegetation, allows the maintenance of highly diverse bird communities, probably due to spatial dynamics among landscape elements.