1. Abraham KF (1980) Breeding site selection of Lesser Snow Geese. Unpublished Ph.D thesis, Queen's University, Kingston
2. Alexander RD (1974) The evolution of social behavior. Annu Rev Ecol Syst 5: 325?383
3. Bertram BCR (1978) Living in groups: predators and prey. In: Krebs JR, Davies NB (eds) Behavioural ecology. Blackwell, Oxford
4. Bishop YMM, Fienberg SE, Holland PN (1975) Discrete multivariate analysis: Theory and practice. MIT Press, Cambridge
5. Brown JL (1964) The evolution of diversity in avian territorial systems. Wilson Bull 6: 160?169