Patterns of habitat use by birds on a well-drained savanna of the eastern Venezuelan llanos

Abstract

We studied habitat use by the avian community during dry and rainy seasons, at La Iguana Experimental Station, a region of well-drained savannahs on the Eastern Llanos, in Venezuela. After three years of field work, we obtained a list of 173 bird species for this area. We carried on surveys by using the Point Count technique, in 86 observation spots, distributed within three habitats: low-lands, forests and wooded savannahs. We quantified the relative abundance of 126 species in these three habitats through both rainy and dry seasons. The low-lands and the forests harbor 97.6 % of the total bird population; however, they cover less than one-fourth of the total study area. The species richness showed seasonal variations in the three habitats, reaching maximum values in low-lands and savannas. Richness increases during the rains in the low-lands, while in forests and savannahs it increases during the dry season. We found evidence of population movements between habitats. The largest movement was observed between savannahs and low-lands. We detected important interactions among bird communities of the three habitats; these three habitats have a large effect in the diversity of birds. Implications of these results for management of the areas in this ecosystem are discussed.