Andrés Felipe Reyes Páez

Andres

andres.reyes@gmx.at

PDF im Hochschulschriften-Service der Universit├Ąt Wien

Bird assemblages along a tropical forest succession gradient in the Pacific lowlands of southern Costa Rica.

Nowadays, human-dominated landscapes in most tropical regions are characterized by a low permeability for forest species, thereby preventing movements between forest remnants. This study quantified the importance of secondary forests in different succession stages as potential stepping stone or corridor habitats for forest birds at the margin of protected forest areas in the Pacific lowlands of southern Costa Rica. Birds were surveyed in pastures with scattered trees and bushes, young secondary forests (actively and passively restored), old secondary forests and old abandoned cacao agroforestry systems (N = 4 replicate sites per habitat type) by point counts (duration: 20 min, 10 counts per site) in November 2010-January 2011. Furthermore, the following habitat variables were measured or estimated: density of large trees, density of small trees, maximal tree height, canopy closure, understory density and herb cover. In total 115 forest bird species were recorded, including 54 forest specialists (restricted to closed forest) and 61 forest generalists. Besides affecting species composition, the density of large trees (dbh > 10 cm) was most strongly related to changes in richness of forest specialists. The species number of forest specialists increased with increasing number of large trees. These results emphasize the importance of large trees as structural component of secondary forests for forest birds. This finding has important management implications for forest restoration programs and calls for evaluating the potential of fast-growing native trees to improve the conservation value of secondary forests for forest birds within shorter time periods.