Bird assemblages of an Iberian cereal steppe

The cereal steppes of Castro Verde (Portugal) support many bird species of high conservation value on which agricultural practices can have significant impacts. The aim of this study was to describe the seasonal variations in bird assemblages using the agricultural landscape mosaic and to explore the potential ecological implications of changes in land use on bird populations. Bird densities and habitat variables were measured in four habitat types (cereal fields, fallow land, stubbles, and ploughed land) during 1997/1998, and detrended correspondence analysis used to summarise information on the structure of bird assemblages across habitats in the winter, breeding and post-breeding periods. Pluvialis apricaria L,, Vanellus vanellus L., Alauda arvensis L. and Anthus pratensis L. were abundant during winter. During the breeding season, bird assemblages were quite distinct across laud use types, with species typical of cereal fields (e.g. Miliaria calandra L.), fallow land (e.g. Melanocorypha calandra L.) and ploughed land (e.g. Anthus campestris L,), After the breeding season, the overlap in bird assemblages increased again, with M, calandra, M. calandra L. and Ciconia ciconia L, being common. Species used different habitats along the year, showing the importance of maintaining the traditional agricultural landscape for preserving the diversity of bird species. The potential impacts of several types of agricultural changes (e.g, agricultural intensification, agricultural abandonment and increase in stocking levels) on the bird populations were discussed on the basis of the results obtained. Any change in the current farming system will probably lead to a decrease in steppe bird diversity. (C) 2000 Elsevier Science B.V. All rights reserved.