Extreme head-tilting in shorebirds: predator detection and sun avoidance
18 – 21
1 April 11
Piet J. van den Hout, Graham R. Martin
Piet van den Hout
Department of Marine Ecology and Evolution, Royal Netherlands Institute for Sea Research (NIOZ), PO Box 59, 1790 AB Den Burg, Texel, The Netherlands
We report observations on extreme head-tilting behaviour in two shorebird species, Baird’s Sandpiper Calidris bairdii and Puna Plover Charadrius alticola foraging at midday, and under a clear sky, on a salt plain in Chile. From the viewpoint that careful interpretation of head postures is essential when studying anti-predation vigilance of foragers, we discuss whether such head postures may be a manifestation of a particular type of vigilance behaviour, whose primary function is the detection of predators in the sky, and/or the avoidance of disability glare produced by imaging the sun on the retina, which generally reduces image quality across the entire visual field.