The Winter Ecology of Harlequin Ducks in Coastal Maine

Mittelhauser, Glen

The following description is taken directly from the abstract: 'Harlequin ducks wintering in eastern North America numbered fewer than 1,000 individuals in the 1980s and were declining at some sites. In 1990, the population was protected from hunting and listed as endangered by The Committee on the Status of Endangered Wildlife in Canada. Little is known about the winter ecology of this endangered population. I conducted winter surveys of harlequin ducks in Maine from 1988-99 and reviewed records in eastern North America to summarize their numbers and distribution, and estimate population trends. I estimate approximately 1,800 birds wintered in eastern North America in the late-1990s. Although this estimate is more than twice the number estimated in the 1980s, additional survey data likely account for much of this increase. Numbers in Atlantic Canada and Maine, which account for ~75% of the wintering population, suggest a recovery in numbers since 1991, coinciding with closure to hunting. At wintering locations south of Maine, numbers have increased since 1970.' 'The largest concentration of harlequin ducks in eastern North America occurs in outer Jericho Bay, Maine where ~1,000 birds winter. Here, I examine habitat use, behavior and diving, and local survival of wintering harlequin ducks. Logistic regression was used to identify habitat variables that are important in discriminating among high and low densities of birds. Higher densities of birds were observed along shorelines exposed to greater wave action, with intertidal substrate consisting of predominantly granite ledge, having higher densities of amphipods and lower densities of chink shells, and having extensive Mastocarpus beds with little Chondrus. Results from feeding behavior analysis suggest harlequin ducks spent the majority of the diurnal period (73%) feeding. Feeding bouts (20 min) were longer than non-feeding bouts (6 min). The duration of feeding bouts did not differ among months, but the duration of non-feeding bouts increased with increasing photoperiod length. The mean dive duration (26 s), pause duration (16 s) and dive pause ratio (1.9:1) did not differ between males and females, but first-winter submerged longer and paused longer on the surface than adult males, perhaps related to the feeding inefficiency of younger birds. Harlequin ducks may have little flexibility in adjusting their winter activity budgets to their environments, especially during prolonged bouts of severe weather. I refined a technique for capturing ducks using decoys and mist nets over floating platforms. A total of 225 harlequin ducks was captured during 16 days of trapping. Females had greater local survival rates than males for both the summer and winter intervals, although these differences donot have strong support. The role of increased male emigration (possibly permanent) on local survival rates remains unclear.' 'My analyses provide some evidence of the beginning of recovery in the population of harlequin ducks wintering in eastern North America since the closure of hunting in 1990; howeer, they remain concentrated at few sites. Given the small numbers distribution, and vulnerability of harlequin ducks in eastern North America, they should remain under full protection in the foreseeable future.' /STUDY LOCATIONS:/ /ISLE AU HAUT/