DIETS OF SHOREBIRDS AT THE BERG RIVER ESTUARY, SOUTH-AFRICA - SPATIALAND TEMPORAL VARIATION

The diets of three common migrant waders; Curlew Sandpiper Calidris fe rruginea, Grey Plover Pluvialis squatarola and Greenshank Tringa nebul aria and three resident species, Blacksmith Vanellus armatus, Kittlitz 's Charadrius pecuarius and Whitefronted Plovers C. marginatus, were s tudied at the Berg River estuary, South Africa from December 1987 to A pril 1989. Direct observations of feeding were combined with analyses of stomach contents, pellets and droppings. Nereid worms, Ceratonereis erythraeensis and C. keiskama, were the principal food of all species studied except Greenshanks, which fed mostly on crabs, Hymenosoma orb iculare. Despite considerable overlap in the diets of all bird species , there were differences in the size classes of nereids taken by diffe rent bird species. Visually-foraging plovers (Charadriidae) were highl y selective, feeding on the largest nereids regardless of their abunda nce. Tactile foragers, represented by Curlew Sandpipers, were non-sele ctive, and consumed different size-classes of worms in proportion to t heir abundance in the substratum. Seasonal variations in the diet of w aders are linked to seasonal changes in the availability of prey speci es.