Intra- and interspecific competition for space in estuarine bird species in a one-prey situation

Intertidal mudflats, where in general many migratory bird species feed at high densities and often in continually changing mixed-species assemblages, offer an opportunity to investigate change in dispersion, habitat shift, or decrease in numbers as a consequence of the presence of other species. Since there are many intervening factors, it remains difficult to prove competition in a field study. A unique opportunity to study intra- and interspecific competition occurred at an intertidal mudflat (North-Ventjager, Holland) because the ragworm, Nereis diversicolor, was the only available prey, whilst despite the one-prey situation, the shorebird diversity was as high as in other European intertidal flats where ten or more prey species comprise the diet.