|Investigating the foraging behaviour of Calidris canutus: can the toxic constraint be alleviated?|
Piek, S. (2017). Investigating the foraging behaviour of Calidris canutus: can the toxic constraint be alleviated? MSc Thesis. NIOZ Royal Institute for Sea Research: Texel. 9 pp.
Red knots are omnivorous shorebirds, that winter in the Banc d’Arguin, Mauritania. In the Banc d’Arguin, the red knots mainly forage on molluscs, of which Loripes lucinalis is by far the most common. Despite its large abundance and favourable flesh-to-shell ratio, red knots prefer other species over Loripes. Through a symbiosis with gill bacteria, Loripes contain relatively large amounts of sulphur. This sulphur likely constraints the red knots in their intake of Loripes. However, starving the Loripes leads to decreased sulphur content, and possibly to higher intake rates by red knots. The intake rates of captive red knots on Loripes that were either fresh or starved for 6, 10 or 22 days were measured through an experiment. It was recorded that the Loripes dry weight intake rate of red knots increases linearly with starvation time, because the birds take less long breaks during foraging. Furthermore, it was recorded that while the experiment ran, the birds started to cope better with eating Loripes, leading to increased intake rates of Loripes, independent of treatment. This, the observation that birds drink less while foraging on starved Loripes and the indication that individual bird characteristics do not seem to influence intake rates help to better understand red knot ecology.