Chick Growth and Development of the Short-tailed Shearwater Puffinus tenuirostris in Tasmania

Abstract

Chick growth of the short-tailed shearwater Puffinus tenuirostris, in a colony in Southern Tasmania was studied from mid January until the end of April 1988. Hatching took place between 10 and 25 January, with the peak occuring on 18 and 19 January. Fledging success was 35%. Mortality was concentrated in the middle of the nestling period and its main cause was predation by poachers and feral cats. Emergence from burrows began, on average, on the 88.7th night (±2.8SD) after hatching, which corresponded to 13.9 April (±2.5SD). After consecutive emergence for 8.8 days (±3.5SD), they fledged on the 97.1th day (±3.3SD) after hatching, with the peak occurring between April 23 and 29. Hatched chicks, on average, had: 10% the body weight, 40% the tarsus length and 50% the bill (exposed culmen) length of adults and attained adult sizes during the middle of the nestling period. Chicks attained the body weight of about 15% heavier than the average adult, however, they lost 25% of the peak body weight over the last three weeks and fledged at the mean body weight 13% lighter than the average adult. As compared with the early growth of their bony organs and body weight, their feather development was delayed. Tails began to sprout at 45.5 days (±2.6SD) after hatching and outer primaries sprouted at 34.2 days (±2.5SD) after hatching. These parts quickly developed in the second half of the nestling period. However, in 1988 the wings and tails of the chicks did not attain adult size and continued developing at the time of fledging. The long nestling period (97 days on average) and the rotation of growth and development of bony and feather parts might be effective for ensuring survival during the nestling period, by reducing the maximum energy demand for growth.