Response of Australian pied oystercatchers Haematopus longirostris to increasing abundance of the beach bivalve prey Donax deltoides

Abstract

This study measured the response of Australian pied oystercatchers Haematopus longirostris on South Ballina Beach, New South Wales, Australia during a recovery in the stock of the primary prey species Donax deltoides, a large beach clam and commonly known as the pipi. It was predicted that oystercatcher counts would increase when pipi abundance increased (numerical response) and that oystercatcher feeding rates would also increase (functional response). Between Oct 2009 and Mar 2015, mean pipi density increased from c. zero to 30 pipis/m2. Mean oystercatcher feeding rates increased to an asymptote of c. 0.26 pipis/min. Breeding season mean counts of adult-plumage oystercatchers increased from 23 to 43, largely driven by non-territorial birds. Prey size selection was absent, both among different prey types and among pipis > 20 mm. This report provides some insights into the feeding ecology of oystercatchers on sandy ocean beaches that should be valuable in planning future studies.