Foraging behaviour of an obligate, sandy shore predator

Abstract

Specialised shorebirds frequent dynamic sandy shore ecosystems yet their foraging behaviour is often poorly known. We examine the effects of environmental (season, tide and level of the beach [zone]) and demographical/social (age, flock size, breeding status) variables on foraging behaviour (foraging rate [bill movements per minute], and foraging success [proportion of successful bill movements]) of a sandy-shore specialist, the eastern Hooded Plover Thinornis cucullatus. We analysed 1190 foraging observations of 217 individually marked birds from 32 Victorian beaches (south-eastern Australia), and separately sampled invertebrate abundance at representative breeding and flocking sites to characterise zonation of prey. The environmental model, namely zone and season, was the best predictor of foraging rate. Both the environmental and demographic models predicted foraging success, where zone, season, tide and breeding status were strong predictors. Immatures had higher foraging rates but lower success than adults. Adults foraged at higher rates near the water's edge but more successfully on the upper beach. Birds foraged with highest success and at the lowest rate during spring. Hooded Plovers rely on all levels of the beach for foraging. Preventing processes that disrupt prey resources, and enhancing prey resources through supplementation of macrophyte wrack may increase prey availability.