Longevity, inter-colony movements and breeding of Crested Terns in South Africa

Abstract

The nominate race of the Crested Tern, Sterna bergii bergii, first breeds when aged three years, but may not be fully recruited to breeding colonies until six years old because many birds do not breed in years of food scarcity. A 21-year-old bird breeding at Dassen Island was the oldest record for the species. There are 109 records in South Africa of birds alive when aged 15 years or older. Of birds whose colony of origin was known, 18% of those breeding and 27% of those present at colonies were at their natal localities. Most cohorts bred at several localities and breeding at most colonies was by birds fledged at several localities. Crested Terns in the Western Cape mainly breed between January and June. Most eggs are laid between January and April. Mean clutch size is 1.02 eggs. At Robben Island in 1987 and 1988 the average number of chicks fledged per breeding pair was estimated to be between 0.48 and 0.59.