Scott G. Gilliland

Evaluating the sustainability of harvest among northern common eiders Somateria mollissima borealis in Greenland and Canada

Sustainable harvest, the extraction of game without affecting population viability, is a desirable approach to the use of wildlife. However, overharvest has been responsible for the decline of many wildlife populations globally, so there is an urgent need to balance human requirements while avoiding the severe depletion of wild populations. Northern common eiders Somateria mollissima borealis are heavily hunted in Canada and Greenland, but the effect of this intensive harvest has not been examined. We developed a population model to investigate the sustainability of the reported harvest, which consisted of two wintering areas in Greenland and Atlantic Canada and three breeding populations. The model indicated that harvest in Atlantic Canada was sustainable, but a number of conditions could lead to slow declines. In contrast, the annual winter harvest of 55,000–70,000 eiders reported during 1993–2000 in Greenland was not sustainable, and this conclusion held under a wide range of alternate conditions. The model indicated that harvest during late winter may have a greater effect on populations than harvest in early winter. We further refined the model to assume that at some low population level the success of hunters would decline and that harvest became a function of population size (a rate). This scenario had the expected and undesirable result of stabilizing populations at very low levels. Overall, our model suggests that the high harvest reported in Greenland during 1993–2000 endangers the sustainable use of the northern common eider population and that management actions are required. Common eider harvest levels in Greenland should be reduced by at least 40% of the 1993–2000 levels to stop projected declines, and allow for recovery of the decimated Greenland breeding population. Encouragingly, new hunting regulations were introduced in Greenland in 2002–2004, and harvest levels appear to be decreasing. If these harvest reductions continue, our population model could be used to re-evaluate the status of populations in the two countries.

Abundance and Distribution of Harlequin Ducks Molting in Eastern Canada

Abstract Until recently, very little was known about the basic ecology of the Harlequin Duck (Histrionicus histrionicus) in eastern North America, including molting locations. A combination of aerial, ground and boat surveys were initiated in 1989 (Québec) and 1994 (Newfoundland and Labrador), and continued through 1999, to locate their molting areas. Molting Harlequin Ducks were found in Labrador, Newfoundland and the Gaspé Peninsula and Anticosti Island, Québec. Coastal areas of southern Labrador, Grey Islands, northern Newfoundland, and Bonaventure and Anticosti Islands, southern Québec, were the most important sites. The tip of northern Labrador and possibly sites along the Québec North Shore and Greenland are the most likely sites where the rest of the eastern population molts. Molting chronology for the ducks in Québec is similar to those on the east and west coast of North America. Now that these sites are known, monitoring and, if necessary, protection of these sites can be considered.

Stomach Contents of Breeding Common Murres Caught in Gillnets off Newfoundland

Abstract We examined the stomach contents of 64 male and 43 female Common Murres (Uria aalge) caught in gillnets during late chick rearing/early chick departure period in August 2002 near breeding colonies in Witless Bay, Newfoundland, Canada. Twenty-six percent of stomachs contained no food. All others contained exclusively fish, and Capelin (Mallotus villosus) was the only fish positively identified. Gravid female Capelin were found in 82% of murre stomachs with contents. The number of fish ingested by murres differed between the sexes, with a mean of 2.7 fish in male stomachs and 1.6 fish in female stomachs. Mean mass of stomach contents did not differ between the sexes (males: 27.0 g; females: 22.6 g). Overall, results were similar to Common Murre diets recorded in the 1980s, despite changes in Capelin distribution and biology. The sample of Common Murres collected as gillnet bycatch was male-biased (59%). Males may have been more vulnerable to being caught in gillnets, perhaps because they were engaged in different activities at this late stage of chick rearing.

Distribution and Abundance of Harlequin Ducks Breeding in Northern Newfoundland

Abstract The number of Harlequin Ducks (Histrionicus histrionicus) wintering in eastern North American is small, and little was known about these birds, especially their breeding distribution. During the breeding period, 990 km of river and streams on Newfoundlands North Peninsula was surveyed where 69 Harlequin Ducks were sighted. Breeding densities varied among watersheds (range 0-0.090 males/km), were slightly lower than elsewhere in eastern North America, and lower than in western North America and Iceland. A total of 128 ± 45 males (indicated pairs) or 284 ± 89 birds (±95% CI) was estimated to occur on the North Peninsula during the breeding season. This may represent 20% of Harlequin Ducks wintering in eastern North America and highlights the importance of the Northern Peninsula as a breeding area for this rare duck.

Movements of Harlequin Ducks in Eastern North America

Abstract The movements of a total of 948 Harlequin Ducks (Histrionicus histrionicus) banded in eastern North America and Greenland from 1996-2003 (313 breeding, 186 molting/staging, and 449 wintering) were examined. Regular resighting and recapture projects have been underway at the Gannet Islands, Labrador, as well as Jericho Bay, Maine. Less consistent observations have been conducted on the Gaspé Peninsula, Québec, and incidental observations were obtained from the public. Affiliations between breeding, molting and wintering sites were assessed in an effort to determine movement patterns and the level of geographic separation. Population affiliations indicated by past satellite telemetry studies were verified by the capture-recapture data. Absolute geographic separation between the eastern North American wintering population and the Greenland wintering population could not be determined.

Composition of Eiders harvested in Newfoundland.

Abstract Somateria mollissima (Common Eider) is an important game species throughout its circumpolar range, including eastern Canada and northeastern United States. In eastern Canada, the largest harvest of Common Eiders occurs in Newfoundland; however, the age, sex, and subspecific composition (S. m. borealis and dresseri are both present) of this hunted population is not well quantified. The species, subspecies, age, and sex composition of the harvest was determined by examining heads collected from 1672 eiders (including Somateria spectabilis [King Eider]), taken mostly by hunters, from 1980–1996. Band-recovery information for Common Eiders banded in Newfoundland and Labrador were also summarized, including data from a release program of hand-reared ducklings in northern Newfoundland from 1988–1996. The composition of the eider harvest varied across the province. In northern and eastern areas, borealis Common Eiders made up the bulk of the harvest. King Eiders were also taken in these areas. In southern areas, most Common Eiders taken were dresseri. Sex ratios tend to be near 1:1, and immature birds comprised most of the harvest. Recovery distributions showed that Common Eiders breeding in Newfoundland and Labrador were mainly taken within the province, but also contributed to harvests in Québec and Nova Scotia, and to a lesser extent, Maine. Hand-reared ducklings had direct recovery rates of 0.047 and were most likely to be recovered within the province in the year of banding, but contributed to harvests in Atlantic Canada and New England as they aged. The harvest of eiders in Newfoundland varies regionally and seasonally; therefore specific harvest regulations could be implemented to manage the variety of populations present in the province throughout the year.

Morphological Variation among Harlequin Ducks in the Northwest Atlantic

Abstract Harlequin Ducks (Histrionicus histrionicus) were captured and measured at a variety of staging, breeding, molting and wintering sites across their Northwest Atlantic range from 1996-2002. The consistency in the body measurements taken on the same birds across time and sites, as indexed by repeatability, was adequate (0.4-0.75), with the notable exception of total tarsus, which showed poor repeatability. Correlations among morphological measurements were weak within each sex. Some differences among locations were detected, notably in wing length, with birds breeding in Labrador showing longer wings than birds breeding further south and those wintering in Maine. Overall, however, major differences among sites were not apparent. Recent satellite and banding information indicate that many of these locations are linked and these observations are supported by this morphological data. Harlequin Ducks are similar to other ducks (except eiders) in that they are wide ranging and have disjunct populations, but show, at best, weak morphological differentiation across their range.

Aspects of Distribution and Ecology of Harlequin Ducks on the Torrent River, Newfoundland

Abstract Harlequin Ducks (Histrionicus histrionicus) breeding on the upper Torrent River of the northern peninsula of Newfoundland were studied from 1993 to 2002. This reach of the watershed was proposed for hydro-electrical development in the 1990s. Harlequin Ducks arrive on the Torrent River as soon as ice-out permits in early to late May. Pairs concentrate in the upper watershed that drains the Long Range Barrens ecoregion. Nesting and brood rearing appear to take place primarily in proximity to spring-pair activity, although movements of more than ten km were observed. Young remain in the upper watershed until fledging in late August to mid-September. Counts of Harlequin Ducks breeding on the upper Torrent River increased throughout the 1990s, and the estimated population growth rate for the Torrent River birds was very similar to the growth rate for birds wintering at Cape St. Marys, Newfoundland (1.14 vs. 1.13) during the same period. Paired females spent ∼ 40% of the day in feeding activities whereas paired males allocated less time to feeding (∼19%) and more time to alert or vigilant behaviors while females fed. Birds rested for 35-40% of the day. Harlequin Ducks exploited rapids, riffles and runs, and were especially associated with the boulder-strewn inlets and outlets of ponds. The large quantities of submerged and semi-submerged angular boulders provide increased surface area for attachments of larval insects, and movement of water through boulders assures high rates of oxygenation important to filter-feeding insects. Broods selected areas with flow rates of 1.27 ± 0.24 m/s. The family Chironomidae contained the most taxa and was the most numerous invertebrate group found in the Torrent River. Chironomidae may comprise the most important food items for pre-nesting Harlequin Ducks when considering volume of prey types consumed. A high rate of brood production in 1997 and 1998, compared to adjacent watersheds, suggests the possibility that the Torrent River system may behave as a source population for the general region of northern Newfoundland.

Effect of Brood Size on Nestling Growth and Survival of Great Black-Backed Gull (Larus marinus) Chicks

Abstract. Morphology, body condition and survival of Great Black-backed Gull (Larus marinus) chicks raised in broods of different size in southern New Brunswick, Canada, were compared. The relationship between age and body size measurements taken from 68 chicks, between 0 and 56 days of age, was analyzed. The logistic model provided the best fit of the morphological measurements (culmen, tarsus, and wing) to age, and the Gompertz model provided the best fit of body mass to age. These models were used to make linear transformations of body size variables that were used in subsequent analysis. There was no difference in the morphology of chicks raised in broods of different size. The first principle component (PC1) from the correlation matrix of the three transformed morphological variables was used as covariate in subsequent analysis to remove variation in body mass that was caused by differences in body size. All chicks were in the same relative body condition at hatch. Body condition of chicks raised in one-chick broods improved with age, that of chicks raised in two-chick broods did not change, but body condition of chicks from broods of three declined with age. In contrast, chicks from larger broods were more likely to survive the nestling period. Although body condition was lower in chicks from larger broods, other factors unrelated to body condition, such as differences in parental quality, led to higher survival for chicks in broods of three.

Morphological Variation Among Herring Gulls (Larus Argentatus) And Great Black-Backed Gulls (Larus Marinus) In Eastern North America

Abstract. Herring Gull (Larus argentatus) and Great Black-backed Gull (L. marinus) morphometric data from various eastern North American locations was collected to examine the sources of variation in body size within and among geographic regions. For Herring Gulls, significant differences in all commonly taken measurements at local and regional scales were found. However, most of the variation in measurements was due to sex differences and the natural variance seen within local populations. Herring Gulls breeding in the Arctic did not show any evidence of being morphologically different from other groups. A discriminant function derived from a Newfoundland, Canada, breeding population of Herring Gulls successfully assigned the sex of birds in Atlantic Canada and Nunavut, Canada, further emphasizing that most of the variation seen is between sexes and not among local or even regional populations. It also indicates that the evitable variation introduced by inter-individual differences in measurements was insufficient to compromise the utility of the discriminant function. The correct classification rate was lower for Great Lakes breeding Herring Gulls, indicating that these birds have different morphologies than those of populations in easterly regions. In contrast, few differences and no clear geographic patterns were found in measurements for Great Black-backed Gulls. These results were consistent with recent genetic information, suggesting an older west to east radiation of Herring Gulls across North America and a lack of isolation among Great Black-Backed Gull populations.