Harlequin Ducks have one the most unique and intriguing life histories of all waterfowl – or most other birds for that matter. While their striking plumage and intriguing migration patterns make them a favored study subject, their actual population sizes and trends are still largely a mystery after years of research by an international cadre of professional biologists.
Harlequin Ducks molt and spend the winter along rocky coasts, often in rough surf. In the spring, they migrate great distances inland to turbulent mountain streams, where they breed and raise their young. The female builds a nest in a secluded spot, usually within a meter of the water. Soon after she is on the nest, the male returns to the coast to molt in a protected Harlequin communal area. The female raises her brood, averaging four young, and then leads them back to the coast in late summer. Harlequins unfailingly pair for life.
Lisa Bate is one of the scientists who have been conducting research on Harlequins. While working as a wildlife biologist for the past decade, she has conducted numerous surveys of these special ducks along their breeding streams in Glacier Park. WIN volunteers and others help Lisa conduct surveys and catch the Harlequins that breed locally, so the ducks can be banded, inspected, and often fitted with tracking devices.
Over the years, Lisa’s Harlequin studies have merged with those of fellow biologists from Montana Fish, Wildlife, and Parks, the U.S. Forest Service, and multiple Canadian wildlife agencies – inland and along the west coast. Collectively, these scientists have surveyed the Harlequin molting, wintering, and breeding grounds, and tracked their movements throughout the year via various forms of electronic surveillance. These experts are tediously learning what specific parameters lead to population swings.
Harlequin Ducks are susceptible to population declines due to their specialized life history. Females always, and only, travel back to their natal streams to breed. Paired males always accompany their mate from the coastal wintering grounds to her natal stream. Every time a female dies, there is one less breeding pair on that stream.
On the negative side, hunting, expanding human encroachment and activities, and shipping accidents lead to population declines. On the positive side, the herring population along the coastal wintering grounds is healthy, so the Harlequins can feast on herring roe before their arduous migration to the breeding grounds. The best news is that additional breeding creeks and streams in western North America are being discovered each year, so the overall population may be less threatened than recently thought.
Lisa and her team of volunteers continue to expand their studies and increase their use of electronic surveillance.