Abstract

ABSTRACT On the weekend of 9thВ­10th October 2004, an unprecedented movement of Redwings Turdus iliacus was witnessed in northwest England.The birds were heading in the unusual direction of east and north instead of the more expected south and west. A search of internet websites enabled this movement to be set in both a national and an international context, and flight-lines and origins of the Redwings to be determined.The influence of the weather, particularly the position of a former hurricane in the Bay of Biscay, was a major factor in the pattern of movements observed.xceptionally large daytime movements of Redwings Turdus iliacus and other passerines occurred over Cheshire, North Merseyside and Lancashire on 9thВ­10th October 2004. The prevailing weather conditions throughout northwest England were moderate NE or ENE winds (force 3В­4) with mostly clear skies and excellent visibility. These were ideal conditions for autumn migration and, since these days were a weekend, birders were out in force, no doubt hoping for a good day's `vis mig' (visible migration). Those who connected withthe thrush flocks were, however, overwhelmed by the numbers involved and astounded by their unprecedented direction of flight: northeasterly on the coast (where almost all autumn diurnal migrants head south or southwest), while inland birds headed north (the usual pattern is west or southwest). Following our investigation of thrush movements in other parts of Britain, and in western Europe, and a detailed examination of the meteorological situation, we aim in this paper to explain the unprecedented movements in northwest England.Detailed