THE ROLE OF OLIVE ORCHARDS IN THE WINTERING OF FRUGIVOROUS BIRDS IN SPAIN

The density of frugivorous birds in parcels of olive orchards in south ern Spain was rated and compared with other habitats bearing fleshy wi nter fruits, mainly wild olive shrubland and other natural shrublands of the Mediterranean area. All olive orchards maintained high densitie s of frugivorous birds throughout the wintering season (November-Febru ary), and showed a very consistent species composition of frugivores. In southern Spain there was a gradient in the density, proportion and numbers of frugivorous species among different habitats; this gradient was related to the level of habitat alteration. The density of frugiv orous birds in the natural Mediterranean shrublands was higher than in the wild olive shrubland and, in turn, higher in the wild olive shrub land than in the olive orchards. Some frugivorous species disappeared along this gradient, whereas others were favoured. Small-sized species decreased most whereas some middle-size species were favoured. This i s most probably because of the structural simplicity, the low fruit sp ecies diversity and the large size of the fruits. In general, frugivor ous species and specifically small-sized frugivorous species were more frequent in southern than in northern Spain.