Scientific Bird Ringing
For more than a hundred years, birds have been marked for scientific projects. Traditionally scientists have used metal leg rings with engraved numbers and the name of the ringing organization. Most of our current knowledge of bird ecology and migration has been discovered through the use of such rings.
Unfortunately metal rings generally provide information only when the bird is in the hand, in most cases, dead. For wild geese, hunters are the reporters of the majority of such data. In rare cases, the bird is recaptured or an observer reads the ring. The vast majority of ringed birds are not reported again after initial ringing.
Because of the low recovery rate of metal rings, scientists developed colour-markers that could be read easily with binoculars. For geese, leg rings and neckbands are common; in other species, wing (petagial)-tags and other markers are used.
For Europe, there is a famous web site that provides information about all known colour-marking projects. For more, click here.
Another option now available for the study of migration is radio-and satellite transmitters. Currently, the latter costs a lot of money and the former, staff time and effort.