Geographical, landscape and habitat effects on birds in northern Spanish farmlands: implications for conservation.

Aims: Farmland habitats in northern Spain are local hotspots of bird richness, sustaining various increasingly rare species and housing huge numbers of migratory birds in winter. This makes them a key habitat for bird conservation. However, they are being negatively affected by conversion to tree plantations, urban developments and infrastructures.

Location: Bird communities in 67 farmland patches which were immersed in a matrix of shrublands and woodlands were studied. These were distributed along a 600 km-long stretch that runs parallel to the northern Spanish coast.

Methods: During June (2005) and January (2006) evaluation was carried out on the effect of farmland patch size, vegetation structure, elevation (a surrogate of climate harshness) and geographical location of farmlands on bird richness and abundance by means of 500 m long transects. Results: Farmland patches with abundant tree and shrub cover scored the highest on abundance and species richness in spring. The size of farmland patch predicted the occurrence of many species in spring and winter, including some that are declining in Europe (eg Lanius collurio, Passer montanus, Miliaria calandra, Alauda arvensis, etc.). In winter, bird abundance increased at low elevation areas and decreased with increasing distance from the main gateway for European migrants entering the Iberian Peninsula at the western Pyrenees.

Conclusions: Results support the idea that easternmost farmlands are particularly important wintering grounds for European migrants and that the increasing deterioration or reduction of lowland farmland patches may affect bird populations. Because such negative effects are likely to increase in the near future, some general guidelines are suggested to apply the legal and budgetary resources of the European Union for better preserving farmland biodiversity in Northern Spain.