Community Ecology and Phylogeography of Bird Assemblages in Arid Zones of Northern Venezuela: Implications for the Conservation of Restricted-Range Bi (Paperback)

Aridlands of northern Venezuela are important from an ornithological perspective because of the occurrence of habitat specialist birds that depend exclusively on desert scrubs for their survival and are almost all endemic to this single zoogeographic region. Currently, long-term survival of habitat specialists is threatened by ongoing changes in vegetation structure and composition but the effects of such changes on bird assemblages are unknown. Limited baseline information on bird assemblages that inhabit aridlands in the Neotropics precludes the implementation of appropriate conservation plans. The goal of this study was to characterize bird assemblages found in six arid zones in northern Venezuela at both ecological and genetic levels, and to generate information relevant for conservation planning in these regions. The study involved assessments of patterns of avian species richness, abundance, community composition and genetic diversity, as well as specific bird-habitat associations. Through systematic surveys, 96 bird species were recorded throughout the study areas. Even though the six areas support a homogeneous habitat type, species richness, composition, and abundance varied among them. The most abundant birds in all six areas were mainly widespread generalist species, and only one of the habitat specialists had high densities in all areas. Species richness was not a good indicator of an area's conservation value, because the protection of the area with highest number of species does not guarantee the effective conservation of all habitat specialist birds. Conservation initiatives for arid zone birds should not only consider species richness and representativeness, but also other factors such as abundance patterns and complementarity between eastern and western areas. Vegetation analyses indicated differences in mean values of both floristic and structural vegetation variables among the six study areas but, overall, the six areas had relatively similar vegetation. Vegetation variables explained more variation in distributions of habitat specialists and generalists when groups were considered separately than when they were combined in a single analysis. Habitat specialists, however, differed in their responses to vegetation variables, which may be related to differences in foraging strategies. Even though habitat specialists did not respond strongly to vegetation variables, results of this study suggest that some structural attributes are important for the survival of this particular group of species. Thus, conservation programs devoted to protect these birds should focus on the maintenance of the structural integrity of the habitat. Molecular techniques were used to investigate patterns of genetic diversity in three codistributed specialist birds (Yellow-shouldered Parrot, Buffy Hummingbird, and Vermilion Cardinal). Multiple analyses indicated geographic structure in the three species, but the extent of geographic structure varied among them as a result of different levels of population isolation during historical times and recent demographic expansions into some of the study areas. The assessment of genetic diversity and geographic structure of these three restricted birds showed incongruent patterns, which evidence different evolutionary histories. Conservation efforts should focus not only on the preservation of genetic diversity in each species but also on the maintenance of the diverse set of processes that generated such patterns.