Bird diversity in tropical dry forest fragments in cattle landscapes of the Department of Cordoba, Colombia.
In Colombia the tropical dry forest is one of the most threatened and least known ecosystems; these have been impacted by different transformation processes and habitat fragmentation, which have affected bird conditions and survival. This research evaluated the influence of landscape elements (forest and pastures with different tree covers) on bird diversity in the tropical dry forest of Córdoba, Colombia. The study was developed within an extensive livestock landscape to characterize the avifauna in four habitat types formed by fragments of secondary forests with different tree cover: secondary forest, pastures with high tree cover, pastures with low tree cover and only pastures. The influence of tree cover on bird diversity was evaluated with monthly samplings in 200 m long transects (per habitat), with two observation intervals (6:00 - 9:00 and 15:00-18:00), from September 2011 to May 2012. A total of 6 667 individuals belonging to 180 species and 48 families of birds were registered. The most abundant species were Columbina talpacoti (5.37 %), Brotogeris jugularis (5.14 %), Tyrannus melancholicus (4.81 %) and Bubulcus ibis (4.80 %). The most abundant family was Tyrannidae (16.4 %), followed by Psitacidae (9.0 %) and Columbidae (8.2 %). The family with the highest number of species was Tyrannidae with 28 species, followed by Accipitridae and Icteridae with 10 species each. The greatest species richness was present in the secondary forest habitat, followed by the pastures with high tree cover, and pastures with low cover. The lowest abundance and species richness was found in pastures without tree cover with significant differences between the habitats (Fisher, p <0.05). According to the Shannon index, the diversity of birds was higher in the secondary forests. In contrast, the lowest diversity was found in pastures without tree cover. The greatest species richness occurred in the months of October and November. In the rest of the sampling period, the number of recorded species and individuals showed some stability. The importance of trees presence in extensive livestock areas was evidenced because they help to contain an important diversity of bird species, and they also generate connectivity among fragments of secondary forests in the cattle landscape.