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 significan t impacts. The aim of this study was to describe the seasonal variations in bird assemblages using the agricultural landscape mosaic and to explore th e potential ecological implications of changes in land use on bird populati ons. Bird densities and habitat variables were measured in four habitat typ es (cereal fields, fallow land, stubbles, and ploughed land) during 1997/19 98, and detrended correspondence analysis used to summarise information on the structure of bird assemblages across habitats in the winter, breeding a nd post-breeding periods. Pluvialis apricaria L,, Vanellus vanellus L., Ala uda 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.), f allow 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, be ing common. Species used different habitats along the year, showing the imp ortance of maintaining the traditional agricultural landscape for preservin g the diversity of bird species. The potential impacts of several types of agricultural changes (e.g, agricultural intensification, agricultural aband onment and increase in stocking levels) on the bird populations were discus sed 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.