Adaptiveness of nest site selection and egg coloration in the African Black Oystercatcher Haematopus moquini

Summary

• 1. African Black Oystercatchers Haematopus moquini select nest sites according to macrohabitat type, local substratum, the presence of plants and other objects at and close to the nest, and shelter. Nest sites in both structurally complex and simple habitats are highly cryptic.

• 2. Eggs are cryptic and there are consistent differences in the patterns of pigmentation between first and second laid eggs within a clutch but between females of the same population overall clutch pattern is similar and only the intensity of pigmentation varies. Within-clutch differences in egg markings did not result in differential predation rates of first and second eggs, but increases nest complexity and hence the crypticity of the clutch.

• 3. Nests are usually sited adjacent to feeding territories. When such sites are not available, birds “leapfrog” over the territories of neighboring pairs rather than attempt nesting in marginal habitats, and may nest several hundred metres away from their feeding territories. Eggs of “leapfrogging” birds had the highest survival and hatching rates in the study area.