Super-normal Clutches and Female-female Pairs in Gulls and Terns Breeding in Poland

Abstract

Abstract Super-normal clutches (five eggs or more) in the Caspian Gull (Larus cachinnans), Mediterranean Gull (Larus melanocephalus) and Whiskered Tern (Chlidonias hybrida) are described. These species have regularly bred in Poland since the beginning of the 1990s. The occurrence of super-normal clutches was 1.8%, 4.1% and 0.3% in the Caspian Gull, Mediterranean Gull and Whiskered Tern, respectively. The first descriptions of a female-female pair in the above species as well as in the Yellow-legged Gull (Larus michahellis) and an unusual mixed female-female pair of two gull species (Yellow-legged Gull and Caspian Gull), never mentioned in the literature before, are also presented. The first fully documented case of a multi-female association of the Mediterranean Gull was also identified. The frequency of the SNCs in this study was higher than in other colonies located in different parts of the geographical range of the species.