Antipredator strategies in breeding Bristle-thighed Curlews

Abstract

Each fall the world’s breeding population of Bristle-thighed Curlews ( Numenius tahitiensis ) arrives on the central Pacific wintering grounds following a migration that entails a non- stop flight of over 5000 kilometers. Sun-drenched, palm-shrouded atolls will be their home for the ensuing eight months. Even in the avian world, however, such apparent luxury is not without costs. For the Bristle-thighed Curlew these costs are incurred on the breeding grounds. From the time they arrive there in early May until they depart again for the wintering grounds in August and September, curlews are exposed to a host of predators. Gyrfalcons ( Falco rusticolus ), Golden Eagles ( Aquila chrysaetos ), Rough-legged Hawks ( Buteo lagopus ), Northern Harriers ( Circus cyaneus ), Parasitic Jaegers ( Stercorarius parasiticus ), Short-eared Owls ( Asio flammeus ), Common Ravens ( Corvus corax ) and Red Foxes ( Vulpes vulpes ) are potential predators of curlews and their offspring. To combat these threats, the Bristle-thighed Curlew has evolved an elaborate suite of antipredator defenses. Depending on the threat and the phase of the breeding cycle, Bristle-thighed Curlews may respond to potential predators by fleeing or flocking, by camouflage or combat. Given the variety of predators on the tundra, a variety of options is critical.