Supernormal clutches in southern African Kelp Gulls Larus dominicanus vetula

Abstract

The Kelp Gull Larus dominicanus typically lays clutches of 1–3 eggs, but larger clutches have been recorded occasionally. We report that four- and five-egg clutches comprise 0.3% of clutches among the southern African subspecies L. d. vetula, with a higher incidence in edges of the species’ breeding range (southern Namibia and the south-eastern Cape) than in the south-western Cape. Supernormal clutches tend to be clustered in specific years and are associated with low hatching success in some but not all cases. Further observations are needed to assess whether such clutches result from female–female pairs, egg dumping, or unusually large clutches laid by a single female.