Nest-site selection and characteristics in a mixed-species colony of Avocets Recurvirostra avosetta and Black-winged Stilts Himantopus himantopus

Abstract

Capsule: Causes of breeding failure determined optimal nest location, Black-winged Stilts being better adapted than Avocets to nest close to water. Aims: To compare nest size and location between the two species and to test whether there were inter-species differences that might suggest specific nesting adaptations, and to investigate possible correlates between hatching success and nest location. Methods: Nest-site selection, characteristics and hatching success were studied during 1989 in a large mixed-species colony located in southern Spain. Results: Black-winged Stilt nests differed in composition and size depending on distance to water (nests touching the water were larger and included mud), but Avocet nests did not. Avocets nests were more aggregated and central within the colony than those of Black-winged Stilts. Causes of breeding failure were flooding and rat predation. Successful or unsuccessful Black-winged Stilt nests did not differ significantly in characteristics or location. Successful Avocet nests were further from water than flooded nests and further from dry land than depredated ones. Distance to the centre of the colony did not affect hatching success. Conclusion: Black-winged Stilts were better adapted than Avocets to nest near water, due to their greater plasticity in nest-building behaviour. Causes of breeding failure determined optimal nest location.