Habitat use by Coots nesting in a Mediterranean wetland

Abstract

The nesting biology of the Coot Fulica atra was studied in the Camargue, Rhne river delta in southern France, where wetlands range from salines and brackish lagoons to freshwater marshes. Coots nested only on the latter. Nesting success depended on drying out of the marshes, and vegetative cover of the nests provided some protection against aerial predators. The density of nests was lower in marshes which dried out early. The distribution of nests in the marshes was related to the distribution of emergent vegetation at least 30 cm tall. Nest distribution changed during the reproductive period as the peripheral parts of the marsh dried out and new emergent vegetation grew up. Regular nest checks revealed that nesting started earlier in years with high water levels and on marshes with large areas covered by emergent vegetation. Nesting started first on Phragmites marsh and on tamarisk trees, followed with a delay of 10-20 days on a mixed vegetation of Typha and Scirpus. Nests were best covered in Phragmites and on tamarisk trees compared with more open nests in Typha and Scirpus reeds. Within each vegetation unit, nests were not constructed at the best covered location, but close to open water. Birds also attempted to nest in open Scirpus reeds and even in shallow ephemeral marshes where nesting was successful only occasionally.