DIET AND HABITAT USE OF THE DOTTEREL CHARADRIUS-MORINELLUS IN SCOTLAND

The feeding ecology of Dotterel Charadrius morinellus adults and chick s was studied on three Scottish breeding areas. On the basis of 2324 p rey items identified from 234 faeces, we show that (i) birds feed sele ctively and (ii) age-related and seasonal differences in food selectio n occur. The diet comprised mainly beetles (Coleoptera), sawflies (Sym phyta) and the adults and larvae of Tipula montana. The faeces of adul t Dotterel contained a high proportion of beetles, whereas chick faece s had more soft-bodied prey. However, when T. montana adults emerged e n masse (every second year) both adults and chicks took more tipulids. On one area, larval T. montana comprised much of the diet soon after the birds arrived on their breeding grounds and just before leaving in autumn. The preferred feeding habitats were flat or gently sloping Ra comitrium lanuginosum or Juncus trifidus heaths or the transition zone between moss heath and montane bog. Dwarf-shrub, grass-dominated and single bog communities were avoided. The preferred feeding habitats we re those in which pitfall trap catches of the main prey were highest. A close juxtaposition of montane bog and R. lanuginosum heaths met the feeding requirements of both chicks and adults, respectively. Recent changes in the breeding distribution of Dotterel in Britain may be rel ated to deterioration in feeding and breeding habitat due to overgrazi ng by sheep and greater habitat acidification.