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Harlequin Duck Population Monitoring in the Strait of Georgia, British Columbia


The Strait of Georgia, which separates Vancouver Island and the British Columbia mainland, supports an estimated wintering population of 12,000 - 15,000 Harlequin Ducks, making it a globally significant site for the species. This year we were fortunate to have received funding from the James L. Baillie Memorial Fund and the Canadian Wildlife Service (CWS) to continue our research.

Whether bobbing down a rapid or crashing in the surf, Harlequin Ducks are always an engaging sight. Until recently, however, little was known about these small sea ducks, whom Newfoundlanders poignantly refer to as "Lords and Ladies". After Harlequins were declared Endangered in eastern Canada in 1990, a concerted effort was begun to ensure that the species did not meet a similar fate in western North America.

The large wintering population of Harlequin Ducks in the Strait of Georgia has been well documented in Christmas Bird Counts. A preliminary review by CWS indicated that the population might be declining. As a result, the Harlequin Duck Working Group (HDWG) was formed and joined with CWS to undertake a long-term study of Harlequin Ducks in the Strait of Georgia.

An intensive banding program began in the Strait in 1993, and soon after, banded birds were being sighted on their riverine nesting grounds and coastal haunts throughout the northwestern U.S., Alberta and British Columbia. Banding is a useful tool because it allows us to make estimates of population numbers with mark-recapture techniques. It also permits us to estimate survival rates, which can help confirm population trends. It quickly became apparent that the Strait of Georgia was the coastal home to a significant portion of Harlequin Ducks in western North America.

The Eastern population declines have been attributed to hunting pressure. That population is currently estimated to be less than 2000 individuals, and is being monitored closely. With so few individuals spread out over a wide geographic area, the Eastern population is extremely difficult to study. The British Columbian population of Harlequin Ducks, probably numbering in the tens of thousands, is, on the other hand, an ideal population to research.

This year, our primary goals were to continue the mark/re-sighting program by maintaining a banded sample of birds in the Strait of Georgia, and to replace worn bands. We also surveyed Harlequin Duck populations at a number of traditional moulting sites.

In spite of an abnormally wet and cold August, which made for difficult field conditions, we managed to capture 318 birds, of which 211 were unbanded and 107 had been previously banded. Approximately 60% of the new birds and 70% of the recaptured birds were male. This is not surprising, given that most males and non-breeding females moult in August, while breeding females moult later in September. Many of our recaptures had been banded in 1993/94 and this provided us with invaluable insights into the species' longevity and site fidelity. The coded plastic bands that we've been using since 1994 appear to be holding up extremely well, especially considering the turbulent environment inhabited by Harlequins.

We recaptured a number of birds which had been banded or observed on breeding streams in the Rocky Mountains. One such individual, was banded as a chick on Swamp Creek, Montana, on 27 July 1995. We also recaptured a number of ‘Alberta' birds, including ones known to nest in Banff National Park and the McLeod River, an area east of Jasper. Interestingly, the McLeod River birds are being studied as part of an environmental impact assessment into the Cheviot Coal Mine, a controversial coal mine being proposed along the boundary of Jasper National Park. Research has demonstrated that a significant proportion of these birds moult and winter in the Strait of Georgia.
Results from 1997 confirm the Harlequin Duck's strong fidelity to moult sites. Approximately 70% of previously banded birds were recaptured at their original moulting location, even as many as 4 years later. A further 20% were captured very near their first banding site, and only 10% had moved in from moulting sites 30-70 km away. This apparently low degree of dispersal raises serious conservation concerns.

Since 1993 we have observed a decline in the population of moulting Harlequin Ducks in the northwestern Strait of Georgia. For example, our largest "catch" was 70 birds at a location which had sported 150 birds or more in years past! This may be attributed to dispersal to other areas, but the high site faithfulness exhibited by Harlequin Ducks does not support that conclusion. Harlequins are directly threatened by development pressures and the increasing popularity of recreational activities along the shoreline of the Strait of Georgia. Because the Harlequins' cryptic eclipse plumage makes them easy to overlook, they are often unwittingly disturbed.

The combination of human stresses on breeding, moulting and wintering habitat may be taking their toll on the western Harlequin Duck population. The species' narrow ecological niche, low reproductive capability, delayed sexual maturity, and specialized habitat requirements limit its ability to adapt to a changing environment. Like grizzly bears, sensitive wilderness species such as the Harlequin Duck are at odds with an increasingly human-modified world. Can we coexist? The future remains to be seen. Clearly, the Harlequin's fate is contingent on our collective willingness to ensure that those requirements are met. This project is an important first step in that direction.

— Kenneth Wright & Peter Clarkson


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