Spatial organization of the Dunlin Calidris alpina L. during winter – the existence of functional units

Abstract

Capsule Dunlin use the same feeding grounds and roosts repeatedly and consistently over long periods of time, giving rise to functional units. Aims To examine the way in which wintering Dunlin organize and distribute themselves in a coastal lagoon. Methods Data collection was undertaken in the Mira Canal and in a salt-pan zone over five winters, mostly using counting, bird ringing and radiotracking. Results Birds restricted their activities to limited sectors of the lagoon, adopting behaviour which they maintained throughout winter. Conclusion The area of the Ria may, therefore, be divided into functional units, i.e. a group of feeding areas and high-tide roosts used by a group of birds, during a certain period of time, corresponding, for example, to winter. This type of spatial organization, already identified in ducks, has not previously been described in waders.