Effects of woodland islets introduced in a Mediterranean agricultural landscape on local bird communities

摘要

This study assesses whether the afforestation approach consisting in the introduction of woodland islets in “agricultural seas” can reconcile the restoration of woody vegetation and the persistence of open-habitat bird populations, providing further opportunities for other forest species to enrich bird diversity at the landscape level. We compared the species richness and abundance of bird communities in a field with 16 introduced woodland islets and in a nearby abandoned field located in central Spain during spring and winter time. The woodland islets presented higher accumulated species richness as well as a higher probability of finding new species if sampling effort were increased only in winter time. These trends were the opposite during spring time. Mean species richness and mean bird abundance were lower at the woodland islets than at the abandoned field in both seasons. We found a higher abundance of open-habitat specialist species in the abandoned field. Woodland islets favoured the wintering of chiffchaff Phylloscopus collybita. We did not find any effects on the only forest specialist species (blue tit Parus caeruleus) in spring. Bird richness and abundance were higher in edge islets than in inner islets. The introduction of larger and mixed plantations connected by hedgerows and a management that favoured the development of big trees, a lower tree density and a diverse shrub layer could promote bird diversity, allowing forest specialists and open-habitat species to coexist at the landscape scale.