Breeding phenology and chick growth in the Brown Booby Sula leucogaster (Sulidae) on Nakanokamishima, Japan

Abstract

We studied the breeding phenology of the Brown Booby Sula leucogaster on Nakanokamishima, southern Ryukyu Islands, Japan. During the breeding season (April-November) of 1989 we observed the presence and absence of 18 chicks and measured their growth on a total of 17 days. Egg hatching was observed during April and May. The estimated minimum pre-fledging period ranged from 60 to 100 days and the maximum pre-fledging period ranged from 86 to 122 days, whereas the minimum post-fledging dependence period ranged from 24 to 105 days and the maximum post-fledging dependence lasted from 74 to 124 days. All of the monitored fledglings left the colony by early-November, and the total period over which parents cared for their chicks was 119-197 days (minimum) and 146-208 days (maximum). Body weight and culmen length attained 95% of asymptotic values in 65 and 69 days of age and wing length in 91 days. Six out of 18 fledglings were seen again in the colony, three to seven years after initial independence.