Songbirds promote connectivity between riparian galleries and adjacent habitats

Abstract

Riparian galleries are among the most vulnerable habitats in the world and are well known for their importance to the most specialized riparian bird species. In this study, we analyzed songbird composition, songbird diet, trophic ecology and seed dispersal in riparian galleries and adjacent Montado matrices in southern Portugal to address the importance of birds in promoting the connectivity between riparian galleries and adjacent habitats. We used fecal samples to compare diet, and blood samples to compare nitrogen stable isotopes from birds in these two habitats. The seasonal variation in the abundance of arthropods and fruits was evaluated in both habitats and seed movement between both habitats was assessed from fruits marked with fluorescence. Abundance of food resources for birds (arthropods and fruits) declined throughout the season in a similar way for both habitats, and there were strong similarities in the diet and trophic ecology of songbirds in the riparian gallery and adjacent habitat. In both habitats, birds preyed heavily on Hymenoptera and Coleoptera but birds more abundant in the Montado fed more on Araneae and Hymenoptera. Seeds were moved significantly more frequently from the riparian gallery into the adjacent Montado than vice-versa. Our results suggest that birds from the adjacent habitat move frequently to the riparian gallery to forage and disperse seeds into the adjacent habitat as they depart. This study shows that birds play an important role in promoting connectivity between riparian galleries and adjacent habitats.