Bird community specialization, bird conservation and disturbance: the role of wildfires

Abstract

1. Although niche theory predicts that disturbance should favour generalist species, the commu- nity-level implications of this pattern have been sparsely analysed. Here, we test the hypothesis that disturbance favours generalist species within communities, analysing effects of wildfires in bird communities in a Mediterranean climate area as a case study.ud 2. We use bird occurrence data in more than 500 1 • 1 km squares forming a gradient running from forest to completely burnt areas. The level of specialization of bird communities was estimated by means of three complementary species specialization indices, calculated for different landscape gradients and averaged at the community level (i.e. 1 • 1 km squares), and mean species rarity.ud 3. We also calculated mean habitat preferences along landscape gradients, as well as an index of conservation value and total species richness.ud 4. Different estimators of bird community specialization varied in contrasting fashion along the wildfire disturbance gradient, and thus we conclude that it is not justified to expect unique commu- nity responses to the sharp variations in habitat characteristics brought by wildfire disturbances.ud 5. Burnt areas tended to have rarer and urban-avoider bird species, whereas unburnt forests tended to have larger proportions of forest specialist species.ud 6. The mean conservation value of communities clearly increased towards the burnt extreme of the wildfire disturbance gradient, while this had a negligible effect on species richness.ud 7. Wildfires seem to play an important role for the maintenance of open-habitat, urban-avoider bird populations in Mediterranean landscapes and also to benefit a set of bird species of unfavour- able European conservation status.ud 8. In this context, it cannot be unambiguously concluded that fire disturbance, even in a context in which fires are greatly favoured by human-related activities, leads to more functionally simplified communities dominated by generalist species.Peer reviewe