1. Arkesson S, Alerstam T, Hedenström A (1996) Flight initiation of nocturnal passerine migrants in relation to celestial orientation conditions at twilight. J Avian Biol 27:95–102
2. Beaman M, Madge S (1998) The handbook of bird identification for Europe and the western palearctic. Princeton University Press, Princeton
3. Bibby CJ, Burgess ND, Hill DA (2000) Bird census techniques. Academic, San Diego
4. Birdlife International (1999) International Species Action Plan: Eleonoras’ s falcon Falco eleonorae. D. Ristow, compiler, unpublished data. http://europa.eu.int/comm/environment/nature/directive/birdspriority.htm
5. BirdLife International (2004) Birds in Europe: population estimates, trends and conservation status. BirdLife Conservation series No. 12. BirdLife International, Cambridge