Rolando A. & Laiolo P. (1994) Habitat selection of Hooded and Carrion Crows in the alpine hybrid zone. ARDEA 82 (1): 193-199

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 Iitalian hybrid zone. Foraging habitat use by the two races 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 similar 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 differentiated when only homotypic groups were taken into account suggesting that mixed flocking series 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 reported by Saino (1992) in another plain area of north-western Italy, where there was a clear differentiation in the use of habitat categories during the winter. These differences, together with those regarding assortative mating, suggest that the alpine hybridization zone might be a mosaic of populations differentiated in relation to the locally diverse ecological conditions.