Roosting birds are caught in winter during night controls. For more specific investigations observations are carried out both within and outside the breeding season, and more specific data are collected with respect to plumage, growth, song, genetic variation etc. In the course of time, the field setup provided an ideal framework for more detailed behavioural investigations. In 1998 the entire computer database was converted to the same format, and it now comprises about 30 different study plots for the two species. Different topics were focused upon in different species, such as migration in the Robin, territory quality in the Nuthatch and sexual behaviour in the Crested Tit.
Many projects therefore combine elements of population ecology and behavioural ecology.
In the early 80s already, ideas appeared in the group to study population processes in large intact habitats and in so-called habitat fragments. The squirrel project was continued by PhD student Goedele Verbeylen. In 1996 the habitat fragmentation project made a large jump with a new project on forest birds and fragmentation in Kenya. About ten different forest birds, including two locally endemic species, are studied in the remaining cloud forest fragments of the Taita Hills. The most important study object is the Taita Thrush Turdus helleri which occurs in three remaining forest fragments totalling less than 400 ha.