HOUT PJ VAN DEN (2009) Mortality is the tip of an iceberg of fear: Peregrines Falco peregrines and shorebirds in the Wadden Sea. LIMOSA 82 (3): 122-133.

The recovery of Peregrine populations in the last few decades triggers the question what impact these raptors have on shorebirds using the Wadden Sea as a staging or wintering site. To answer this question, we took advantage of results of a four-winter study on raptor predation on shorebirds on the Banc d'Arguin, a key wintering site for shorebirds on the East-Atlantic Flyway. We suggest that in the Wadden Sea, as on the Banc d'Arguin, populations of wintering shorebirds are not regulated through direct consumption by predators. Instead, raptors may have a profound intimidating impact on (groups of ) shorebirds, which induces the latter to engage in a wide spectrum of anti-predation behaviours and body composition changes. This means that shorebirds pay predation costs by means of foregone opportunities affecting their long-term survival and reproduction, rather than by direct mortality.
      In a predator-prey game of anti-predation measures against stealth, predators will try to exploit vulnerabilities of their prey. Because of this, especially inexperienced birds or migrants which are unfamiliar with the habitat are prone to being depredated. However, also fattening (spring) migrants may suffer considerable predation costs, and these may increase in the near future, as growing numbers of Peregrines breed in the Wadden Sea region.

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