Neotropical migrant landbirds and landscape changes in Los Tuxtlas, Veracruz, Mexico

Faced with the problem of habitat loss and with the need to preserve the remaining components of the original avian biodiversity in neotropical regions such as Los Tuxtlas, it is imperative to determine how the neotropical migrant bird species have responded to the anthropogenic alterations of their natural habitats. To provide data in this direction, we censused neotropical migrant birds in undisturbed and in disturbed forest fragments and in regeneratlng forests (young second growths and old second growths). In addition, we conducted censuses in the following man-made habitats: arboreal agricultural habitats (cacao, coffee, mixed, citrus, and allspice), non-arboreal agricultural habitats (corn and jalapeno chili pepper), live fences, and pastures. We censused 4186 neotropical migrant birds representing 71 species. Seven species (Magnolia Warbler, Hooded Warbler, Wilson's Warbler, American Redstart, White-eyed Vireo, Yellow-rumped Warbler, Black-and-white Warbler) accounted for 50% of total records. Isolating distance was an important variable influencing species richness at the non-pasture habitats studied. Disturbed forest fragments had significantly fewer species and individuals than undisturbed forest fragments and than regenerating forests. Pastures were the poorest habitat in neotropical migrant birds. Agricultural habitats, however, were particularly rich in individuals and species (3479 individuals of 59 species). Arboreal agricultural habitats and live fences were richer in species and in birds than non-arboreal man-made habitats and were also the habitats most similar to the undisturbed forest fragments in species assemblage. We discuss the conservation value for neotropical migrant birds of agricultural habitats and of live fences as landscape elements that help reduce physical and biotic isolation among the remaining configurations of forest fragments and compensate, in part, for the loss of vegetation area and habitat heterogeneity that has resulted from anthropogenic activity in Los Tuxtlas.