Harlequin Ducks in Iceland

Abstract In Iceland, the Harlequin Duck (Histrionicus histrionicus) is generally distributed as a breeder on rapid clear-water streams, from sea level to about 700 m. Densities are generally low, except at the headwaters of streams draining productive lakes where blackflies (Simulium vittatum) are abundant. In northwest, north and east Iceland, molting Harlequin Ducks are found in similar localities as the wintering birds, but molting birds are largely absent from the southwest coast. During the molt, the birds often stay close to cliffs or rocks and are hard to find. Harlequin Ducks winter on exposed rocky coasts and densities are correlated with substrate as indicated by shore exposure. In 1998-2001, the total wintering population of Harlequin Ducks in Iceland was estimated at 14,000, with 95% confidence limits of 12,000 to 16,000. Assuming that migration in and out of Iceland is insignificant, the total Icelandic breeding population is 3,000-5,000 females, or three to five females (pairs) 100 km-2. A d...