Alpine Chough (Pyrrhocorax graculus) Science Article 2
We analysed the call repertoires of the Red-billed Chough (Pyrrhocorax pyrrhocorax) and the AlpineChough (Pyrrhocorax graculus) across three continents (Europe, Asia, and Africa) for intraspecific and interspecificdifferences in call-repertoire size and discuss the factors that could have promoted its evolution.
Paola Laiolo, Antonio Rolando, Anne Delestrade, and Augusto De Sanctis, Can. J. Zool. 79: 1568-1576 (2001)