Ardea
Official journal of the Netherlands Ornithologists' Union

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Zwarts L. (1990) Increased prey availability drives premigration hyperphagia in Whimbrels and allows them to leave the Banc d'Arguin Mauritania in time. ARDEA 78 (1-2): 279-300
Whimbrels Numenius phaeopus preparing for their spring departure from the Banc d'Arguin were able to increase their daily food intake to 1.5 times the winter level. This was made possible by an increase in the proportion of the day during which their prey were available. First, their main prey on the beach, the fiddler crab Uca tangeri, occurred more frequently on the surface. Second, two other crab species that were taken from eelgrass beds, Panopeus africanus and Callinectes marginatus, were more active later in the spring. It would not be possible for Whimbrels to increase their body mass faster than they actually did because a digestive bottle-neck limited the rate they could ingest food (Zwarts and Dirksen 1990). Neither would they be able to start gaining mass earlier because of the low prey availability during that period. Consequently Whimbrels simply could not leave the Banc d'Arguin for their European stopover sites before the end of April. The annual cycle of the Whimbrel appears intimately geared to the annual cycle of their tropical prey species.


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