The effects of grassland management using fire on habitat occupancy and conservation of birds in a mosaic landscape

摘要

Prescribed burning is routinely used to improve grazing in Pyrenean rangelands affected by an overall trend of land abandonment. This study considers the environmental variables influencing habitat occupancy by birds and the consequences of the use of fire in range management for bird conservation. Bird use and habitat structure of 11 cover types, the result of specific management regimes, were monitored for two breeding seasons in a mosaic landscape. Three main gradients of avian composition, corresponding to tree cover, shrub volume and grazing intensity, were identified from canonical correspondence analysis. The structure of the bird community seemed more intensely affected by species-specific selection of cover types than by the birds' use of multiple patches. Out of a total of 10 bird species analysed by a simultaneous confidence intervals procedure, four species with an unfavourable conservation status in Europe (Emberiza cia, Lullula arborea, Saxicola torquata and Lanius collurio) preferred managed grassland. Three types of grassland with shrubs (derived from single or repeated burning) had the highest bird conservation index (taking into account specific status and abundance of the bird assemblage), whereas forests showed middle or low values. The relation (P = 0.054) of this index to the logarithm of the pastoral value (which includes density and grazing quality of grasses) in currently managed cover types suggests that the objectives of grassland recovery by appropriate management practices and those of bird conservation coincide in our study area.