Influence of habitat fragments on bird assemblages in Cork Oak woodlands.

摘要

Capsule: Fragments of olive groves and riparian galleries have a positive influence on bird assemblages in Cork Oak woodlands. Aims: Assess the impact of fragments of olive groves and riparian vegetation on the birds of the matrix of Cork Oak woodland. Methods: Bird point counts at increasing distances (0, 50, 150, 250 and 350 m) from 15 olive groves and 13 sectors of riparian vegetation embedded in a matrix of Cork Oak woodland to determine species assemblages and species abundance. Results: A total of 72 bird species were recorded during the spring, and 61 in winter. The diversity of the bird assemblages of the Cork Oak matrix was somewhat greater near fragments. The density of six out of the 17 most abundant bird species varied due to the presence of olive groves or riparian vegetation. Of those, five were more abundant near the fragments and only one was less abundant. These effects could be mostly predicted from the species' density in the fragments of olive groves and riparian vegetation and depended on the season. Conclusions: In Mediterranean landscapes dominated by Cork Oak woodlands, the maintenance of the existing networks of olive grove fragments and riparian galleries has a positive effect on the bird assemblages of the woodland matrix. The increase in abundance of birds near olive groves and riparian galleries is probably due to the additional fruit resources provided by the fragments, especially in winter. We conclude that active maintenance of the existing fragments should be included in the management of this valuable agricultural-silvicultural-pastoral system.