Ecology and breeding biology of the common buzzard Buteo Buteo, in Ireland

Biogeographical patterns have implications [or interactions between species and can result in regional variation in resource use and behaviour. This thesis examines the current status, ecology and prey selection of an avian predator. the common buzzard Buteo buteo living at the western edge of its biogeographical range in Ireland, a large island at the extreme western fringe of Europe (53 oN. 7°W) where diversity of prey and competing avian predators is relatively low, as the population continues to expand following extinction from Ireland sixty years ago. The core breeding population of buzzards in now covers a third of the island and indicates influx of birds of Britain and continental Europe which is further supported by the level of heterozygosity in the population. High relatedness between individuals over large areas also suggests a high frequency of long distance dispersal by individual buzzards within Ireland. The current population is estimated at 3,312 breeding pairs in Ireland. With a potential carrying capacity of the island of 23,374 breeding pairs. Buzzard dietary breadth gets wider towards the west of their range across Europe. and is particularly wide in Ireland. This suggests that raptor species at the edge of their range, where resources are reduced and environmental pressures increased, have to be highly flexible if they are to survive. A supplementary feeding experiment showed that prey abundance is particularly limiting in the early stages of the breeding season, and productivity of buzzards in Ireland related to the amount of rabbit in the breeding season diet. However, a fifth of the breeding season diet was made up of corvid species indicating the importance of alternative prey. Trophic upgrading, through determining why so many species of birds of prey have been unsuccessful in natural population recovery in Ireland, and community restoration are required if we are to return to sustainable, dynamic and species rich ecosystem in which the buzzard is no longer dominant.EThOS - Electronic Theses Online ServiceGBUnited Kingdo