Towards an efficient indicator of habitat quality for Eastern Curlews on their intertidal feeding areas

Abstract

ABSTRACT Migratory shorebirds feed in intertidal wetlands during the winter non-breeding season, to meet their daily needs and accumulate reserves for the flight to their breeding grounds. However, these habitats may be impacted by development. Eastern Curlew (Numenius madagascariensis) populations are declining in Australia, where we assessed relationships among the curlews’ feeding behaviours, prey types, broad substrate types, feeding microhabitat preferences, and population density, across 11 tidal flats in Moreton Bay, South East Queensland, Australia. Most prey were crustaceans, of varied size. Within flats, the types and rates of feeding actions, and feeding success, varied with sex, microhabitat and tidal stage. Among different flats, the estimated rate of prey biomass intake was strongly correlated with curlew density, explaining 57 per cent of its variation (2–77 birds/100 ha); whereas neither feeding attempts nor successful feeding acts per unit time were good density predictors. Substrate resistance was negatively correlated with both biomass intake and curlew density, because curlews were able to use their long bills to extract larger prey from deep burrows in more penetrable flats. The curlews, therefore, chose feeding areas directly according to food supply, but the substrate penetrability provides a promising rapid indicator of regional-scale variation in habitat quality.