Hooded Crow (Corvus corone cornix) Science Article 1
The Carrion Crow (Corvus corone corone) and the Hooded Crow (C. corone cornix) have parapatric ranges in Europe with narrow areas of hybridization. Reproductive biology of populations of Carrion and Hooded crows and hybrids is described for four areas in northern Italy. Nonrandom mating was observed in a hybrid zone. Homogamic pairs were observed more frequently than expected by chance. Data on clutch size and reproductive success were analyzed for Carrion Crows and Hooded Crows in allopatry, and for parental and hybrid phenotypes in a hybrid zone. Clutch size did not vary across the hybrid zone. Pairs with Hooded Crow females in the hybrid zone produced significantly more chicks than those with hybrid females. The number of chicks recorded from Carrion Crow females was higher than for hybrid females, but not significantly.
Nicola Saino and Simona Villa, The Auk 109(3):543-555, 1992