An experimental investigation of the effects of shorebird and flatfish predation on estuarine invertebrates

Shorebirds and flatfish were selectively excluded from areas of mudflat of the Ythan estuary in two separate experiments. Exclosures and control areas were monitored over several months for sediment and faunal characteristics and compared by 2-way ANOVA. There was no significant effect of the exclosures on sediment properties, due to the relatively large open area of the exclosure material used. Exclosures had little effect on invertebrate densities. The results are discussed in relation to prey mobility and the effects of predation estimated from energy demands of the predators. It is suggested that, over the study period, predators did not significantly affect the numbers of invertebrates in the mudflats. Over the winter period, Corophium within exclosures were significantly larger than those in control areas, probably due to size-selective predation by shorebirds.