Social systems

Some Palaearctic species maintain long-term territories during their stay in Africa (for Whinchat Saxicola rubetra see Dejaifve 1994; for Pied Flycatcher Ficedula hypoleuca see Salewski et al. 2000; for Acrocephalus, Hippolais, Luscinia see Cramp 1988, 1992), and at least some return to the same territories in successive years (for Marsh Warbler Acrocephalus palustris see Kelsey 1989, for Great Spotted Eagle Aquila clanga see Meyburg et al. 1995). Others set up temporary territories at different successive areas that they occupy, or very short-term territories as they defend fruit and nectar sources. Yet other species are found in flocks or solitarily depending on their food supplies, and seem continually on the move. Others, such as Wood Warbler Phylloscopus sibilatrix and Willow Warbler P. trochilus, form single-species flocks, or even mixed-species flocks along with African species (Brosset 1984, Demey & Fishpool 1994). In such flocks, aggression is seldom observed, even though many birds forage close to one another.

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