peter_clarkson@pch.gc.ca (peter clarkson) sent this comment:

Harlequin Duck

Harlequin Ducks have very specific breeding habitat. They select sections along small, clear turbulent streams and rivers (not wetlands & open water areas). These areas are likely selected because they sustain a relatively high abundance of freshwater aquatic invertebrates, the harlequin's primary food during the breeding season. Because these invertebrates in turn are filter feeders, and thrive in areas of high water quality, harlequins depend on maintenance of good water quality, and sites with minimal sedimentation. For that reason they are felt to be good indicators of freshwater aquatic health. Harlequins nest along the shore, often close to the water's edge. Studies have found them nesting on the ground (under shrubs, logs, etc.), in logjams, on cliffs and canyon walls above the stream, and occasionally in tree cavities. The females appear to be philopatric to breeding sites, and both sexes have strong fidelity to coastal moulting and wintering areas. Long term pair bonding is common. Migratory movements are east-west. Recent studies have found some birds which breed in Northern Quebec and then migrate to coastal Greenland. The Harlequin Duck is listed as an endangered species in eastern Canada, was recently declared threatened in Maine, and is under petition to be listed under United States Endangered Species Act (it is currently Category 2). Western populations are suspected to be in decline, particularly those that winter in the Strait of Georgia, BC. They are also believed to have disappeared from historic breeding areas in California, Colorado, British Columbia and Washington State. For the most recently published species range and distribution map see the Harlequin Duck Status and Distribution Report prepared by the Harlequin Duck Working Group (1993).