Influence of farming activities in the Iberian Peninsula on the winter habitat use of common crane (Grus grus) in areas of its traditional migratory routes

Farming activities can influence bird habitat and wintering patterns. Changes in the wintering habitat use of common crane (Grus grus) were related to changes in land use on this species' traditional migration route in the Western Palaearctics. The study was conducted in the Orellana area (Extremadura, SW Spain), the most important wintering area on this route, where the continued availability of natural food resources (acorns, bulbs, invertebrates) represents a more balanced diet than agricultural resources alone. The presence of crops such as corn (Zea mays I,.) is, however, not a critical factor in the area, since the two types of resources, natural and agricultural, are available in the same period of time. The increase in area dedicated to irrigated crops, especially rice (Oriza sp.), affected the growth in the numbers of wintering cranes in the Orellana area. In the past the peak wintering period was in December and was positively correlated to acorn production, whereas the peak period is now in January-February, coinciding with the use of rice-held stubble as feeding places. Dehesas (Mediteranean scrub), cultivated or not, may replace rice-field stubble as feeding places. The existence of intensive farming activity in combination with traditional land-uses is suggested to be the cause of these changes. (C) 1999 Elsevier Science B.V. All rights reserved.