Methodology

The study of living birds by the banding method, whereby great numbers of individuals are marked with numbered aluminium leg rings, has come to be recognised as a most accurate means of ornithological research. (Frederick C. Lincoln 1935.)

The development of any area of science depends heavily on the methodology available. Migration studies began in the simplest possible way, by observation, and have developed over the past 120 years by the addition of progressively more sophisticated methodology, including in recent years the use of miniature radio-transmitters to track individual birds on their journeys. At no stage, however, has any method been dropped from the arsenal, and systematic observations can be just as revealing now as they were 120 years ago. In this chapter, different study techniques are described, highlighting their pros and cons. Two hundred years ago practically no evidence was available that birds migrated, apart from their seasonal appearance and disappearance in particular areas. Hibernation was often thought to be responsible for the disappearance of many species from high latitudes in winter, a notion that gained support even from the scientific community, but again without evidence.

An early indication that individual birds could actually travel long distances to winter elsewhere was provided by a White Stork Ciconia ciconia which was seen in Germany in 1822 flying around with a spear stuck through its body. When the bird was shot it was found that the spear could be attributed from its design to a part of West Africa. This probably provided the first firm indication from Europe of a long-distance movement by an individual bird. Since that time, more than two dozen other storks have been recovered in Europe in similar circumstances. In more recent times, bird migrations have been studied by observations (made directly or with radar), by bird counts made in particular places at different dates, by widescale surveys of bird distributions at different seasons, by use of ring recoveries, or in recent years by the use of radio-transmitters and other devices fixed to individual birds which can then be followed on their journeys.

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