Conflict of interests: The authors declare no conflict of interests.
Differential mortality of wintering shorebirds on the Banc d’Arguin, Mauritania, due to predation by large falcons
Version of Record online: 21 AUG 2008
© 2008 The Authors. Journal compilation © 2008 British Ornithologists’ Union
Special Issue: Birds as predators and as prey
Volume 150, Issue Supplement s1, pages 219–230, August 2008
How to Cite
VAN DEN HOUT, P. J., SPAANS, B. and PIERSMA, T. (2008), Differential mortality of wintering shorebirds on the Banc d’Arguin, Mauritania, due to predation by large falcons. Ibis, 150: 219–230. doi: 10.1111/j.1474-919X.2008.00785.x
- Issue online: 21 AUG 2008
- Version of Record online: 21 AUG 2008
- Received 25 September 2007; revision accepted 5 October 2007.
- annual survival;
- habitat selection;
- non-lethal effects;
- Red Knot
Predators may influence many aspects of the daily life and seasonal movements of their prey. Here we quantify direct, and evaluate indirect effects of predation by three falcon species (Lanner Falcon Falco biarmicus, Barbary Falcon Falco pelegrinoides and Peregrine Falcon Falco peregrinus) on coastal shorebirds wintering on the Banc d’Arguin, Mauritania, an area hosting approximately 30% of the East Atlantic Flyway population of shorebirds. On the basis of 754 h of observation over five winters, 97 witnessed attacks and 585 collected prey remains, we show that shorebirds were safer in larger flocks, which tended to be attacked less often. Furthermore, species that forage relatively close to shore and in small flocks were depredated more often than expected from their relative abundance. In three species, Red Knot Calidris canutus canutus, Bar-tailed Godwit Limosa lapponica taymyrensis and Dunlin Calidris alpina, the juveniles were more vulnerable than adults. We estimated that on average 1% of the juvenile and 0.1% of the adult Red Knots present were killed by large falcons each winter. For Red Knots we simultaneously quantified annual survival on the basis of an individual colour-marking programme: mortality due to predation by falcons accounted for an estimated 6.2% (juveniles) and 0.8% (adults) of annual mortality. We suggest that juvenile Red Knots are 10 times as likely to be killed by falcons because they use riskier habitats, i.e. early and late tide foraging areas closer to shores where surprise attacks are both more common and more successful. These results indicate that the strength of indirect effects of predation operating in a shorebird population largely outweigh the effects of mortality per se.