Ardea
Official journal of the Netherlands Ornithologists' Union

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Michaelsen T.C. & Byrkjedal I. (2002) 'Magic carpet' flight in shorebirds attacked by raptors on a migrational stopover site. ARDEA 90 (1): 167-171
When attacked by predators many bird species form flocks, within which individuals may reduce risk by specific positioning behaviour. Shorebird flocks often attempt to escape raptor attacks by twisting and turning in coordinated flights. We studied responses to raptor attacks of mixed flocks of Dunlin Calidris alpina and Common Ringed Plovers Charadrius hiaticula on a marine mudflat in Western Norway. Instead of twisting and turning flights reported from other studies, the flocks, when attacked, commonly (88% of 128 attacks) rushed in straight line out over the sea, forming a flat 'carpet' (median flock depth 0.5 m) close above the surface (median 0.8 m). This flight pattern seemed to prevent Peregrine Falcons Falco peregrinus, responsible for a majority (60%) of the attacks, from effectively using their preferred stooping mode of hunting. Peregrines, like the other raptors seen, hunted mainly by surprise attacks or in pursuit flights level with the flocks, and this appeared to put individuals in the rear of the flocks at risk. The observed risk-evasive urge to stay low and to fly fast in order to keep abreast with the front of the flock, seemed to have created the 'magic carpet'


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