Movements And Survival Of Molting And Wintering Harlequin Ducks

Robertson, Gregory J.
Cooke, Fred
Goudie, R. I.
Boyd, W.S.
Canadian Wildlife Service

Movement or emigration can significantly effect estimates of survival obtained from capture-mark-recapture (CMR) studies. We estimate both movement and survival of a molting and wintering population of Harlequin Ducks (Histrionicus histrionicus) in coastal southwestern British Columbia. Over 150 individuals from two populations 15 km apart were marked with individually identifiable colored tarsal bands. Surveys were conducted at both sites throughout the entire non-breeding period. At the main study site of White Rock, complete population counts were taken and the number of unmarked birds in the population was also assessed. Significant movements of individuals were detected all throughout the non-breeding period. A number of males and females departed from the study area after the molt in the fall, only to be replaced by an influx of birds from other molting sites. The timing of this movement differed between the sexes as the females molt approximately six weeks later than the males. An additional influx of birds, mostly unpaired males, occurred in the spring before departure for the breeding grounds. Exchanges between the two sites appeared to biased in one direction. More birds moved from the inland site to the more coastal site than vice versa. Furthermore, more females (9 of 47) than males (1 of 50) made this move. Young (second and third year) females were more likely to move out of the study sites or exchange study sites than adult females. Annual return rates were similar in the first year of the study (65% of females and 74% males) however fewer females, (54% of females and 80% of males) returned in the second season. We documented only one mortality (a male) during the non-breeding period. The lower apparent survival of females may be due to a truly lower survival rate or a function of the greater propensity of females to move between areas of suitable habitat.

Harlequin Duck Participant in LIA study: "When I used to go hunting, different species of birds were getting scarcer, like the harlequin ducks, they were declining fast. I used to see them in all the bays in the 1970s to the 1980s." (Williamson 1997:36) The harlequin duck is a relatively uncommon seaduck considered unique among North American waterfowl because of its discontinuous distribution and its habit of breeding along swiftly flowing streams (Bellrose 1976; Todd 1963; Dzinbal 1982; Williamson 1997: 36). COSEWIC has designated the eastern North American population as endangered. The breeding distribution (Figure 18.1) of this population includes southern Baffin Island, Ungava Bay, northern Labrador, the Gaspé Peninsula, Hudson Bay, James Bay, and western Newfoundland (Montevecchi et al. 1995). Goudie (1989) estimated the former (during first European contact) size of this population at 5,000-10,000. Vickery (1988) examined the winter distribution of this population during the 1980s and estimated less than 1,000 known individuals within coastal Newfoundland, the Maritimes, and New England (Figure 18.1). Goudie (1989) suggests hunting as the dominant factor for the decline.

Species of Special Conservation Status
The species of special conservation status selected for consideration in this assessment are harlequin duck, peregrine falcon, polar bear, and beluga whale. These species were chosen because they have low abundance and are protected under the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) and Canada's international commitments (e.g., International Agreement for the Conservation of Polar Bears) for their protection, and all of these species occur regularly in or near the VBNC Claim Block. Other species of special status, such as the wolverine and Atlantic walrus, are infrequently reported to occur in the Landscape Region (Brice-Bennett 1977:129; Williamson 1997:31 and Map 4). Neither of these species nor the Eskimo curlew (an endangered shorebird) are likely to occur in the Landscape Region. 18.1 Existing Environment Species that are low in abundance require special consideration for their protection and to maintain biodiversity. COSEWIC has established a classification system to designate the vulnerability of endangered species (COSEWIC 1996):
* extinct - no longer exists;
* extirpated - no longer existing in the wild in Canada or a region of Canada, but occurring elsewhere;
* endangered - facing imminent extirpation or extinction;
* threatened - likely to become endangered if limiting factors are not reversed; and
* vulnerable - of special concern because of characteristics that make it particularly sensitive to human activities or natural events.

Figure 18.1 Distribution of Harlequin Ducks in Eastern North America

Recent surveys by the Canadian Wildlife Service within the breeding area of the eastern North American population (Montevecchi et al. 1995), the Department of National Defence (LFA 1992; JWEL 1992; JWEL 1994; JWEL 1995; JWEL 1996; JWEL 1997a), Hydro-Quebec (Morneau and Decarie 1993), and VBNC (JWEL 1997b) suggest that the current population is likely larger than that suggested by Vickery (1988). This is consistent with increasing trends in numbers at traditional wintering sites since the late 1980s and early 1990s.