The use of ringing to monitor changes in the numbers and demography of birds

Abstract

Knowledge of changes in the abundance and demography (productivity and survival) of birds is essential if conservation problems are to be identified and remedied. Bird ringing is the only way to monitor avian survival rates and can provide an effective means of monitoring changes in numbers and productivity. In this paper, we briefly review past and present applications of bird ringing for the purpose of monitoring numbers and demography, and suggest ways in which current monitoring may be improved. In order to monitor survival from recoveries of dead birds it is important that more than one age class of birds are ringed, and serious statistical problems can arise when most birds are ringed as chicks. While the breeding season is generally the most useful time of year to ring birds for the purpose of monitoring, organised winter ringing may be useful for species which show strong fidelity to wintering sites and are therefore likely to be re trapped in subsequent winters. The Constant Effort Sites philosophy of maximising retrap rates while standardising (or at least measuring) catching effort should be extended to other groups of birds.