ROSEATE TERN BREEDING BIOLOGY AND FACTORS RESPONSIBLE FOR LOW CHICK PRODUCTION IN ALGOA BAY, SOUTH AFRICA

Abstract

Summary Randall, R. M. & Randall, B. M. 1981. Roseate Tern breeding biology and factors responsible for low chick production in Algoa Bay, South Africa. Ostrich 52:17-24. Roseate Terns Sterna dougallii were studied in 1977 on St Croix Island, Algoa Bay, South Africa. They are winter breeders in Algoa Bay and remain away from the breeding islands until about three weeks before the first eggs are laid. Full breeding dress is usually attained by the time the chicks hatch, when red appears on the culmen. Reasons are given for regarding the red culmen as an intraspecific aggressive signal. Nest density was 0,2/m2 with a mean nearest neighbour distance of 0,66 m ± 0,27 m. Mean size of first clutches was 1,32 eggs, of replacement clutches was 1,03 eggs. Eggs measured 42,1 mm (39,8-44,5 mm) x 30,1 mm (28,6-31,5 mm). In clutches of two eggs, first eggs had significantly larger volumes than second eggs. Incubation took about 25 days and one of the pair did most of the incubating. Rearing took less than 28 days and ...