1. In western Europe, the number of bird species present in summer remains fairly constant at 187-229 between latitudes 35 and 65 degrees N, decreases to 156 by 70 degrees N, and then markedly to 26 and 24 on islands at 75 and 80 degrees N. The number present in winter decreases steadily with latitude from 211 at 35 degrees N to four at 80 degrees N, reflecting the greater withdrawal of species from northern latitudes in winter. 2. The proportion of summer visitors in the local avifauna in summer also increases with latitude from 29% of breeding species at 35 degrees N to 83% of breeding species at 80 degrees N. Conversely, the proportion of winter visitors in the local avifauna in winter decreases with latitude, from 36% of wintering species at 35 degrees N to 8% of wintering species (mostly seabirds) at 70 degrees N to none at 80 degrees N. 3. At most latitudes in the range 35-70 degrees N, while some species leave for the winter, a smaller number of other species move in, mostly from further north. About 23% of breeding species leave western Europe totally in autumn to winter elsewhere, most in Africa south of the Sahara but others in southern Asia and elsewhere. Conversely, 3% of wintering species leave western Europe totally in spring to breed elsewhere, some to the north-west in Iceland-Greenland-Canada and others to the north-east in northern Siberia.
