References
- Bekoff , M. and Byers , J. A. 1981 . Behavioral Development , Edited by: Immelmann , K. Cambridge : Cambridge Univ. Press .
- Cramp , S. and Simmons , K. 1980 . The Birds of the Western Palearctic , vol. II , Oxford : Oxford Univ. Press .
- Pandolfi , M. and Pino d'Astore , P. R. 1990 . Avocetta , 14 : 47 – 52 .