Each spring, they disappear inland to rushing mountain streams to mate and rear young. OSU wildlife professor Bob Jarvis and graduate student Howard Bruner have spent three field seasons walking up many miles of rushing Oregon Cascade mountain streams, searching for breeding and nesting harlequins. Until the OSU study, very few harlequin duck nests had ever been found in Oregon. Male harlequins come inland only to breed. They return to the coast as soon as females begin incubation.
Predation is the most common cause of nest failure.
Biologists have yet to determine the culprits. Otters, minks, bobcats, raccoons, skunks, ravens and coyotes are all suspect. They seem to prefer steep slopes with thick plant cover, a clear flyway to the water and streams with boulders and logs. They nest on the ground, on stumps or in cracks on rocky slopes, and line their nest with a thick layer of down. Jarvis plans on continuing to band and study harlequins to learn more about how long they live and whether the young return to their home stream or disperse to other streams.