The Use of Bird Rings in the Study of Survival

Bird ringing was mainly used o riginally to study bird migrati on . However, it was reali sed as early as 1928 that encounters ( recoveries) of dead ringed birds contain information on survival-mortality processes. Lack was the ~ first to investigate surv ival processes in bird populations based on ringed --~~_ individuals, with attention to age dependence in su rv ival. Starting from early historical references I review surv ival studies in bird populations, along z_1 three lines of development. The ups and downs of analyses of recove ries : ^-~_ the ups concern the development of models making clear the difference between a table of recoveri es and the classical life table of demographers ; the downs concern in particular problems of identifiabi lity in age-dependent models. The development of models and analyses of live recaptures , _ in particular in relation to long-term studies in bird population biology. Reflections on the unique characte ri stics of bird ringing. One outstanding characteristic is the possibility of ringing birds at birth and in tam of esti~ mating immature survival, which encourages the development of joint analyse s --_= of recoveries and recaptures to overcome the limitations of analyses of recoveries or recaptures in isolation . Examples of su rvival analyses in gull s Larus spp. and Great Cormorants Phalacrocorax carbo are used as i llustra_ -tions. Strategies for ringing based on these reflections are discussed . --~_ _ ~^~