The identification of wild birds with aluminium rings or colored rings ("bird ringing") has been an important methodological component of ornithological field research for more than 110 years. It has also been standard practice at the Konrad Lorenz Institute of Ethology for decades.
Bird ringing is an internationally recognized standard method for population monitoring of native wild bird species, among other things. It is recommended in the EU Birds Directive (EU Birds Directive 2009/147/EC/Art. 10/ Annex 5) and clearly described and regulated in the guidelines of other ornithological institutions, such as the German Ornithologial Centres at Radolfzell and Helgoland. Data on species, sex, age, biometric measurements (e.g. length of wings, feathers, and tarsus; weight) and condition indices are routinely recorded during bird ringing. In the long term the individual identification and measurement of breeding and migratory birds allows scientists to assess changes within different bird populations. This can subsequently yield important conclusions on external influences (e.g. climate change). This would not be possible by using only simple visual and audible counting methods.