HABITAT SELECTION OF HOODED AND CARRION CROWS IN THE ALPINE HYBRID ZONE

Habitat selection of co-existing Hooded Crows Corvus corone cornix and Carrion Crows C. c. corone was studied in the Susa valley, an alpine valley in the Italian hybrid zone. Foraging habitat use by the two rac es was not significantly different during the autumn-winter whereas it was during the spring-summer when Hooded Crows preferred meadows and Carrion Crows preferred dunged fields and maize stubble. However, if s imilar habitat categories (e.g. meadows and dunged meadows, maize and maize stubble) were combined, differences were no longer statistically significant. Resource selection by the two crows was more differentia ted when only homotypic groups were taken into account suggesting that mixed flocking serves to standardize ecological choices. Analysis of flocking behaviour showed a clear tendency to avoid heterotypic flocks . The results of habitat selection are not in keeping with those repor ted by Saino (1992) in another plain area of north-western Italy, wher e there was a clear differentiation in the use of habitat categories d uring the winter. These differences, together with those regarding ass ortative mating, suggest that the alpine hybridization zone might be a mosaic of populations differentiated in relation to the locally diver se ecological conditions.