1. Adriaensen F, Dhondt AA, Van Dongen S, Lens L, Matthysen E (1998) Stabilizing selection on blue tit fledgling mass in the presence of sparrowhawks. Proc Royal Soc Lond Series B-Biol Sci 265:1011–1016
2. Alatalo RV, Lundberg A, Bjorklund M (1982) Can the song of male birds attract other males—an experiment with the pied flycatcher Ficedula hypoleuca. Bird Behav 4:42–45
3. Andrewartha HG, Birch LC (1954) The distribution and abundance of animals. The University of Chicago Press, Chicago
4. Baeyens G (1979) Description of the social behavior of the magpie (Pica pica). Ardea 67:28–41
5. Birch LC (1971) The role of environmental heterogeneity and genetical heterogeneity in deterining distribution and abundance. In: den Boer PJ, Gradwell GR (eds) Proceedings of the Advanced Study Institute on 'Dynamics of Numbers in Populations' Oosterbeek 1970. PUDOC, Wageningen, pp 109–128