2002 Volume 34 Issue 1 Pages 39-59
Chick growth and fledgling performance of Streaked Shearwaters (n=89 in total) were studied on Mikura Island (33°52'N, 139°14'E), Izu Islands, Japan, in 1985 and 1990. Chicks hatched in mid August (13th, 17th) on average, with a mean body mass of 59-73g (11-13% of 552g mean adult mass). Adults stayed with their chicks for four days on average after hatching. Exposed culmen, tarsus, and wing lengths of chicks at hatching were 42%, 38% and 8% of mean adult sizes of 49, 51 and 310mm, respectively. Chicks attained mean adult body mass at around 40 days old in mid September. Peak body masses (734-739g) were reached on average in mid October at around 70 days old, and were about 33-34% heavier than mean adult size. Weight recession prior to fledging resulted in the loss of 30% of the peak body mass over the last three weeks, and chicks fledged at body masses of 519-522g that did not significantly differ from the 508g mean adult or subadult masses in autumn. Individual chicks increased body mass in an erratic fashion at intervals of from a few days to a week throughout the nestling period. Body mass and bony parts (culmen and tarsus) attained maximum increase rates (13.8g, 1.0mm and 0.6mm/day, respectively) by days 9-22, while flight feathers as well and tail feathers that emerged at 39 days on average, grew most rapidly at about 62-75 days (3.0mm/day [for remiges] and 4.3mm/day [for rectrices]). Chicks fledged almost at adult sizes (adult body mass and lengths of culmen and tail, but with 2% shorter tarsus and wing than adults). All of the growth rate constants ks, were very low at 0.05 for body mass, exposed culmen and wing, and at 0.08 for tarsus (only the tail constant was higher). These low values were typical of semi-precocial birds. Last feeding of chicks by parents occurred when chicks were 82 days old (7 November) on average and chicks were not fed for nine days on average prior to fledging. The mean length of the nestling period was 90-91 days, which ended on 13-17 November on average. Fledging success rate for chicks that had hatched was very low (21%) at the colony near the garbage dump, compared with two other areas with less human activity (68-72%). Most chicks were lost due to predation by feral cats and rats.
