A number of bird species are known to be involved in the transmission cycles of at least two Borrelia species in Europe. Recent evidence suggests that the European blackbird (Turdus merula) and song thrush (T. philomelos) are the dominant hosts in these cycles. Examination of a suburban garden used as a winter roosting site for the European starling, Sturnus vulgaris, revealed an extremely high density of Ixodes ricinus nymphs and adults of up to ca. 50 ticks/m2, suggesting that this common, flocking avian species could also be of major epidemiological significance. Sampling of microhabitats showed that the ticks had not accumulated under the bamboo roosting site but had moved predominantly to open grassy areas. Both adults and nymphs were found to be infected with Borrelia valaisiana and/or Borrelia garinii.