Bird ecology in cloud forests

The Taita Hills consist of small and isolated patches of pristine cloud forest which are embedded in anthropogenic landscapes, such as agricultural fields and plantations of exotic trees. The connectivity among local populations living in these forest patches strongly depends on species´ dispersal behaviour. Species with specific habitat demands often remain inside their habitat, and thus can be classified as highly sedentary species.

Studies on the movement ecology of forest specialist bird species living in a highly fragmented environment underline how habitat size, isolation and habitat quality impact movement behaviour. Telemetry studies may provide valuable information on movement, home-range sizes, site-fidelity, and species-specific habitat demands. In this study, we observed the movement behaviour of the Cabanis’s greenbul, Phyllastrephus cabanisi, a cooperatively breeding bird species. We surveyed the behaviour of breeding females eleven days post-hatching of their offspring. We analysed movement patterns of the females and of all other present color-banded flock members on a daily basis. We did these observations in different forest fragments, differing in size, isolation and habitat quality, namely Ngangao, Chawia, Vuria and Susu cloud forest fragments.

Depending on habitat fluctuations and specific habitat demands throughout the year home ranges of Cabanis’s greenbuls flocks may vary seasonally. We hypothesize that movements of the entire flock during the fledgling phase may be limited due to food provisioning and the protection of the rather immobile offspring. During the nonbreeding season, however, subpopulations may remain relatively well connected and small forest fragments may act as essential stepping-stones connecting populations of the larger forest patches within the meta-population network. This study was conducted by Kim Mortega, Beate Apfelbeck, Musa Makomba, Jack Kiiru, Peter Kafusi, Laurence Chovu, Oliver Mwakio, Johann Klackl and John Maghanga, in collaboration with Christina Fischer and Jan Christian Habel. This activity was in close collaboration with a three-years research project on species under stress “Avian life history in the anthropocene – a study of physiological, morphological, behavioural and fitness responses to rapid habitat change in an east african forest specialist (anthrobird)”, funded by the German Research Foundation (DFG).