Interaction of predators and manmade object causes potentially significant mortality in a wintering shorebird population

We repeatedly observed Dunlin Calidris alpina pacifica (n = 30) killed by collisions with a fence wire following raptor attacks at a single winter roost at Humboldt Bay, California, USA. If raptor-related collisions occurred at the observed rate over an entire winter, fatalities at the site represented approximately 4% of the local Dunlin population. The regularity of collisions may have promoted specialized behavior in individual avian predators (Peregrine Falcon Falco peregrinus) and scavengers (Western Gull Larus occidentalis) to exploit the situation. We are unaware of other reports of significant shorebird mortality resulting from the interaction of raptor attacks and a manmade object.