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.