Spatial distribution of wintering oystercatchers (Limicolae) and intestinal parasite load

Some oystercatchers are less efficient predators than others because of the ir age or their feeding habits. This lower feeding efficiency may reduce th eir survival or their chance of migrating to nesting grounds. Do these bird s carry more parasites? To address this question, we studied the intestinal parasite load of oystercatchers hibernating in the Exe estuary (Great Brit ain) in relation to their feeding site, type of prey, and parasite load of mussels, their main prey in the estuary. We show that some birds with lower feeding efficiency carry more parasites, particularly the potentially path ogenic nematode Capillaria sp. The degree of infestation by trematodes thro ugh the mussel Ptilostomum brevicolle is not related to the degree of infes tation of the mussels themselves. We suggest that some birds are resistant to infestation.