Landscape changes and breeding bird assemblages in northwestern Portugal: the role of fire

Fire is a major driving force of landscape change in the Mediterranean regi on. The objectives of this paper were to explore the implications of landsc ape change and wildfires in a region of northwestern Portugal for the diver sity of breeding birds. Land use cover for the years 1958, 1968, 1983 and 1 995 was obtained from aerial photography for a study area of 3700 ha. Breed ing bird assemblages in each of six land use categories were characterized in 1998 using point counts. The main landscape changes in the study area ac ross the 40 years were a decrease in the area of agricultural land and low shrublands (respectively 29% and 48%) and an increase in forests and tall s hrublands (both over 95%). Bird assemblages showed increased richness and d iversity across the gradient: low shrublands --> tall shrublands --> conife r --> mixed --> deciduous --> agricultural areas. Many of the species with narrow niche breadth (specialists) were associated with agricultural areas and deciduous forests. In spite of the low diversity of burned areas (mostl y shrublands) a few specialist species depend on this habitat. Thus, the cu rrent fire regime probably contributes to maintaining bird diversity at the landscape level. There was an inverse relationship between landscape diver sity and estimated bird diversity across the last 40 years. Landscape manag ement actions to preserve bird diversity should focus on the maintenance of agricultural land and deciduous forests. In parallel, a wider use of presc ribed burning and grazing is suggested. This would contribute to maintainin g low shrublands in the landscape, useful both as an habitat for some bird species and as fuel breaks for preventing the occurrence of large wildfires .