Short-term effects of reclamation of part of Seal Sands, Teesmouth, on wintering waders and Shelduck : I. Shorebird diets, invertebrate densities, and the impact of predation on the invertebrates.

Abstract

The invertebrate macrofauna of Seal Sands, Teesmouth, is very limited in species composition. Nereis diversicolor has a two-year life cycle; the larger size-class provides the main prey of the birds Pluvialis squatarola, Numenius arquata and Limosa lapponica. Hydrobia ulvae is an important food of P. squatarola and Calidris canutus. Small Carcinus maenas occur in late autumn and are taken by the larger shorebirds. Small Macoma balthica are also taken, but are scarce and not an important bird food. Tadorna tadorna and Calidris alpina subsist chiefly on species of small oligochaetes and polychaetes which occur at very high densities (Gray 1976). Feeding areas of the shorebird species show some segregation, particularly in groups of species taking the same prey. It is calculated that birds removed about 90% of the standing crops of large Hydrobia and Nereis during a single winter. This followed the reclamation of more than half the intertidal land used as feeding grounds by the birds.