Intertidal Lanice conchilega reefs as feeding grounds for wading birds in the bay of the Mont Saint-Michel (France)
De Smet, B. (2011). Intertidal Lanice conchilega reefs as feeding grounds for wading birds in the bay of the Mont Saint-Michel (France). MSc Thesis. Ghent University: Gent. 45 pp.
Intertidal areas are known to attract huge amounts of birds by providing resting areas and breeding and feeding grounds. Biogenic habitats occurring along intertidal flats, such as reefs composed of the tube-building polychaete Lanice conchilega, can be particularly important as feeding grounds for foraging birds. The attractiveness of the L. conchilega reefs can be attributed to their habitat complexity and especially the high abundances of associated macrofauna. Evaluating the importance of those benthic communities as a potential food supply for waders and waterfowl is fundamental for understanding their feeding ecology and therefore the adaptation of species to their habitats. In this respect, gaining knowledge on the diet composition of birds is necessary. This study proposes an evaluation of the functional importance of intertidal L. conchilega reefs for wading birds in the bay of the Mont Saint-Michel (France); an area known to be of international importance as a migration site for birds. Bird counts were made both in the entire bay and the L. conchilega reefs with the aim of assessing whether the wading bird community differed between the areas. Furthermore, the alimentary regime of waders feeding in the reefs was investigated by means of a faecal analysis. The composition of wading birds, without taking into account the bird abundances, can be considered the same in both areas. When abundances were included, observed bird frequencies in the reefs were approximately 30 times higher than expected assuming a uniform distribution of the birds over the whole bay. This clearly demonstrates that birds are attracted by the reefs. Within the reefs birds do feed on L. conchilega, but high abundances of associated macrofauna, and especially crustaceans, were detected in their faeces as well. Although bivalves are very abundant in the reef benthos, they only constitute a minor part of the investigated bird diets. Comparing the diet composition of different wading birds species reveals only small differences, mainly attributable to crabs, L. conchilega and amphipods. A feeding behaviour combining traits of both selective and opportunistic feeding strategies seems to be the case in the L. conchilega reefs.
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