Growth, fledging success and post‐fledging survival of juvenile Oystercatchers Haematopus ostralegus

We studied the consequences of differences in growth rate on the subsequent survival of Oystercatcher Haematopus ostralegus chicks. Fledging success increased sharply with growth rate, from zero in chicks growing at less than 6 g per day to about 85% in chicks growing at more than 10 g per day. The age at which chicks fledged varied from 27 to 52 days. Chicks which fledged at an early age displayed a much faster growth rate than later fledging chicks. Although slow growth resulted in a considerable prolongation of the period before fledging, slow‐growing chicks fledged at a smaller size and with a lower body‐weight than fast‐growing chicks. After fledging, all chicks remained almost completely dependent on their parents up to an age of 3 months and often longer. Almost 40% of the fledglings eventually returned to the breeding area. This figure probably reflects post‐fledging survival. Age and size at fledging had no effect on a chick's probability of return. Body‐weight at fledging had a small positive correlation with the return probability, but this was not statistically significant. We conclude that although slow growth severely reduces a chick's chance of fledging, it probably does not result in irreversible damage causing an increased risk of mortality during the first years after fledging. Apparently, any possible disadvantage associated with small size or low body‐weight could be compensated for after fledging.