His books with John Krebs helped to define the field of behavioural ecology, the study of how behaviour evolves in response to selection pressures from ecology and the social environment.[3]
His study of a small brown bird, the dunnock, linked detailed behavioural observations of individuals to their reproductive success, using DNA profiles to measure paternity and maternity, and revealed how sexual conflicts gave rise to variable mating systems including: monogamy, polygyny, polyandry and polygynandry.
His studies of cuckoos and their hosts have revealed an evolutionary arms race of brood parasite adaptations and host counter-adaptations.
Other studies include: territory economics in pied wagtails; contest behaviour and mate searching in butterflies and toads; parent-offspring conflict and the transition to independence in young birds.
William Bate Hardy Prize of the Cambridge Philosophical Society, 1995[4]
Medal of the Association for the Study of Animal Behaviour, 1996
President of the International Society for Behavioural Ecology, 2000-2002
British Trust for Ornithology / British Birds "Best Book of the Year Award" in 2000 (for Cuckoos, Cowbirds and OtherCheats) and in 2015 (for Cuckoo - Cheating by Nature).
Frink Medal of the Zoological Society of London, 2001
^Milinski, M. 2012. Nature 485, 444. Royle, Nick J. (2013) Book Review: An Introduction to Behavioural Ecology, Animal Behaviour, Volume 85, Issue 3, March, Pages 686–687.