PARENT-OFFSPRING FEEDING RELATIONSHIP OF COOTS (FULICA-ATRA) IN A VARYING ENVIRONMENT

Predictions derived from parental investment theory indicate that when the reproductive value of offspring decreases, parental investment should also decrease. If so, it should be expected that in adverse years, parental investment should be lower, given the lower survival prospects of chicks, than in more favourable years. I tested this by recording the Frequency with which coots (Fulica atra) fed their chicks during a ten tears period in a set of lakes that experienced considerable interannual variations in water levels. Contrary to the prediction, I found that during drier years, chicks were Fed more frequently than during wetter years, in which self-feeding by chicks was more frequent. The reason for this could he that for coots the crucial factor For improving reproductive success is the quality rather than the quantity of chicks. and by increasing parental effort during more adverse years, the lower survival prospects of chicks could be attenuated. However, late in the breeding season, when fledging success is lower, chicks were fed by their parents less frequently than in the early breeding season. This could be related to a change in the cost/benefit ratio, itself independent of offspring quality, that parents experience when rearing chicks late in the season due to the start of plumage moult.