Research topics

The research in our group addresses various aspects of the behaviour of birds. Currently, our efforts are concentrated on the study of sexual imprinting in small passerines (see species). Through this work we try to reveal some of the mechanisms underlying interspecific brood parasitism, as well as hybridization and speciation.

In the examination of these subjects, we utilize populations of tits and pied flycatchers living just outside of Oslo, Norway. Experiments are conducted in woodland plots in which several hundred nest boxes have been placed. Study populations have been maintained for many years, with some dating back as far as 1968. Extensive interspecific cross-fostering in these populations has been carried out since 1997, so that young have been raised by parents of a different species (tits by other tits and flycatchers by tits). This set-up allows us to separate the effects of inheritance and environment on behaviour of offspring and, in particular, to study the extent and significance of sexual imprinting.

Through doctoral and post doctoral grants and master projects we conduct detailed studies of the behavioural and life-history consequences of the cross-fostering regime. For instance, we investigate variations in survival, dispersal, and mating and reproductive success among groups, both in blue tits and in great tits. Specifically, we test the aggressive response of cross-fostered birds towards intruders on breeding territories (Hansen & Slagsvold 2003), as well as their social dominance status as exhibited on feeding stations during the winter (Hansen & Slagsvold 2004). Further, we record song in cross-fostered individuals to determine whether song characteristics are innate or learned, and if learned, from whom they learn. Song analysis are performed in co-operation with Professor Helene M. Lampe at our department. As results to date indicate that cross-fostered birds have more difficulty in finding a mate, we also collect blood samples from parents and offspring to investigate the occurrence of extrapair paternity in our cross-fostered populations in relation to rearing condition. These results are also analyzed with respect to paternal investment relative to the male's share of the paternity. Genetic analyses are performed at the Lifjeld Lab in co-operation with Professor Jan T. Lifjeld and his team.