Print BB May 2005
Weather and bird migration Norman Elkins Richard Johnson ABSTRACT Bird migration in and through Britain and Ireland shows great variation, both seasonally and annually. Much depends on atmospheric conditions, which can equally hinder and assist migration, both on a broad scale (the distribution, extent, intensity and movement of pressure patterns), and at a local level (temporal and spatial changes in wind, visibility, cloud and precipitation).All the parameters of bird migration, including timing, routes, speed and duration of migration, are affected, and modified, by a number of meteorological factors, probably the most influential being wind speed and direction.This paper reviews the influence that weather has on bird migration in Britain and Ireland, and discusses examples of the major types of migration. A number of unusual or exceptional migration events are discussed and illustrated with appropriate weather charts. Introduction long-distance expeditions traversing half the Migration is one topic that never fails to appeal planet, such as those by Arctic Terns Sterna par- to the whole spectrum of those with an interest adisaea and Barn Swallows Hirundo rustica,to in birds, from the inveterate ‘twitcher’ to the local movements in response to the temporary general public. Bird migration, defined simply freezing of freshwater bodies. Differences in as regular movements from one area to another, migration strategy and behaviour result in generally occurs in response to the availability some species undertaking nocturnal migration, of food resources and encompasses an enor- while others move mainly during daylight mous variety of methods. These range from hours. These differences operate not only 238 © British Birds 98 • May 2005 • 238-256 126.
[Show full text]