Bird Ringing for Science and Conservation

Understanding Bird Migration - The Need for Bird Migration

A flying bird can quickly move long distances and this makes it possible to migrate regularly between areas that are suitable during different periods of the year. In areas with strong seasonality, migratory birds can successfully take advantage of a short but very productive summer to breed and raise young. At northern latitudes, such as northern Europe, most of the breeding bird species are migratory and leave for some period of the year. In most areas of the world, climate and/or food availability varies over a year. This means that annual movements, in order to increase survival, can be advantageous everywhere. Migration is a most important key to the large and fascinating diversity of birds in the world.

The variation in migratory behaviour is extremely large; some birds move only short distances, while others can migrate vast distances to wintering areas in the southern hemisphere. Some species move on broad fronts while others follow very narrow routes. Irruptive movements occur in several northern species in response to food shortage.

Recoveries of Ospreys ringed in Sweden and reported during the period August-November show that this species migrates on a broad front.

The original purpose of bird ringing was to unravel the mysteries of bird migration. Within Europe the broad patterns of migration are now known for most bird species. In recent decades the member countries of EURING have greatly intensified their efforts in the area of migration research. The computerisation of the archives of recovery data has been a prerequisite for many of the recent recovery analyses and also for producing national
recovery atlases. Comprehensive atlases have been published in several member countries and work has begun on them in a number of others. This is an important step because it will make results from ringing easily accessible. It will also show where knowledge is missing and where efforts in the future ringing should be focused. As migration pattern change over time, particularly in relation to factors such as climate change, continued bird ringing is important even for common species.

Parallel and narrow migration routes shown by different populations of Chaffinches ringed during passage at two bird observatories in Europe. Black dots refer to recovery places of birds ringed at Courish Spit, Russia (filled square) and open dots refer to birds ringed at Col de Bretolet, Switzerland (open square).

Migration is a challenge within nature conservation work since many populations of birds regularly move over huge areas, and problems en route or in the wintering quarters can result in declining breeding populations in areas far away. Many migratory birds are declining in numbers and detailed information about the annual
movements, including important stop-over sites and winter quarters, is a top conservation priority.

Large numbers of ringing recoveries are now held in the EURING Data Bank and they can be used to analyse more complex questions about bird migration. Results of such analyses could form the basis of detailed
laboratory and field research into the navigational cues and fuelling strategies that birds use when migrating.