AN ANALYSIS OF THE MORTALITY AND SURVIVAL OF HARTLAUB'S GULL

Abstract
Underhill, L. G. & Underhill, G. D. 1986. An analysis of the mortality and survival of Hartlaub's Gull. Ostrich 57: 216–223. Ringing recoveries of Hartlaub's Gulls Larus hartlaubii ringed at Robben Island and Rondevlei are analysed. The variation in the recovery rate between cohorts of chicks ringed on Robben Island on the same day and between years is attributed to initial mortality (mortality after ringing but before reaching the mainland). Estimates of initial mortality are negatively correlated with total rainfall (a measure of storminess) during the breeding season, indicating that stormy weather contributes to breeding success, presumably through increasing food availability. The survival probabilities of first-year, second-year and adult Hartlaub's Gulls are estimated, and found to be independent of year.