Common Eider

Somateria mollissima


The Birds Of America by John James Audubon
Common Eider.]
FULIGULA MOLLISSIMA, Linn. [Somateria mollissima.]

Evidence of Population Declines among Common Eiders Breeding in the Belcher Islands, Northwest Territories.
GREGORY J. ROBERTSON, ACWERN, Univ. of New Brunswick, Fredericton, NB.
And H. GRANT GILCHRIST, CWS, Prairie and Northern Region, Yellowknife, NWT.

Information regarding the status of common eiders Somateria mollissima breeding in the Canadian Arctic is lacking. In 1997, we surveyed five island archipelagoes in the Belcher Islands in Hudson Bay (56 00'-57 30'N, 79 30'-80 00'W) from 3 - 23 July 1997. Our results were compared with eider surveys of the same islands completed between 1985-89 using a standard protocol. This study represents the first population trend data of any common eider population breeding in the eastern Canadian Arctic. 1416 nests were found on 431 islands; most (94.1%) while the female was still incubating. In every region, the number of nesting eiders declined significantly (overall = 75.0%, range: 62.3% - 84.0%). In 1997, nesting islands and adjacent waters were free of ice, eiders laid large clutches (range: 4.0 - 4.4, 1.0-1.2 SD), and, they nested early. These conditions are indicative of a good nesting season, and we conclude that extensive non-breeding by female eiders in 1997 does not account for the observed decline. A large die-off of eiders during the winter of 1991-1992, which occurred when areas of open water froze, is the most likely cause of the decline. Our results present serious conservation concerns because eider populations are sensitive to reductions in adult survival, and this population is harvested throughout the year by subsistence hunters.

Importance Of Common Eiders In An Intertidal Community: Predation, Disturbance, And Indirect Effects
 HAMILTON, DIANA J. Department of Zoology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1
NUDDS, THOMAS D. Department of Zoology, University of Guelph, Guelph, Ontario, Canada, N1G 2W1

Intertidal community ecology is an extremely well developed field. However, sea ducks are frequently neglected in intertidal community studies, because they are viewed as transient or not sufficiently numerous to have an effect. This may be a mistake, because recent work with other aquatic birds indicates that they can be very important in structuring communities. We examined the importance of Common Eiders (Somateria mollissima) as predators in an intertidal invertebrate community in Passamaquoddy Bay, New Brunswick, Canada. Eiders are present here year-round and feed heavily on blue mussels (Mytilus edulis), a dominant intertidal invertebrate. We erected predator exclusion cages in disturbed and undisturbed areas of the lower ntertidal zone. Disturbance involved manually removing 80% of all biomass present, and was intended to simulated a catastrophic abiotic event. We sampled invertebrates from cages and paired control areas from 1994-1996. Total biomass and species diversity were compared among treatments, disturbance levels, and times using split- plot ANOVA. Variation in abundance of common species was examined using a similar multivariate model. Eider predation significantly reduced invertebrate biomass within 4 months in undisturbed sites, and after 8 months Eiders had eaten 40-50% of biomass in both areas. Disturbance delayed effects of predation, but ultimately allowed them to persist longer in the system. Predation had little effect on total species diversity, but did generate indirect effects on, and interactions with, other species. Exclusion of Eiders led to an increase in dogwhelks (Nucella lapillus) (a gastropod predator of blue mussels) within one year at undisturbed sites. This in turn obscured the impact of ducks on mussels in these areas. Eiders are also size-selective predators, preferring mussels of 15-30 mm in length. This affected size-frequency distributions of the prey population, and has implications for future Eider-mussel interactions, as well as indirect effects on the invertebrate community. Clearly, Common Eiders play an important role in this community, and our results show that sea ducks should not be neglected in community studies.

The effect of body condition on subsequent creche attendance in Common Eiders (Somateria mollissima)
Kim Mawhinney, University of New Brunswick
Creches are groups containing any number of adult female(s) and duckling(s), two or more of which are parentally unrelated. Several authors have suggested that the body condition of ducks is a determining factor in parental care and that females in poor condition more readily abandon their young. In 1997 and 1998, 285 adult female Common Eiders breeding on Green Island were captured and nasal tagged. Our objective was to examine the relationship between adult female condition, using multiple measures of body size, and subsequent membership in creche. The body was higher than average for females tending a brood and the body condition of abandoning females was lower than average regardless at which point they were captured in the incubation period. "Aunties" are females without young which assist brood-caring females in defending a brood. Females that were in good condition and hatched and lost their own ducklings became aunties; and females that lost their clutch early enough in incubation such that they were in good condition when ducklings in the colony hatched became aunties.

Pre-hatch brood amalgamation in common eiders: why do eiders adopt eggs?
GREGORY J. ROBERTSON, Dept. Biol. Sci., Simon Fraser Univ., Burnaby, BC.
Pre-hatch brood amalgamation(intraspecific nest parasitism) was studied for three years (1991-1993) in a colony of common eiders (Somateria mollissima) breeding near Churchill, Manitoba. The amalgamation rate was highest (42.4% of nests) during the year with the highest nest density and good environmental conditions, and was lowest in the year with low nest density and poor conditions (20.2% of nests). Over the nesting season, foreign eggs were laid at the same time as normally laid eggs. Most foreign eggs were laid while the attendant female was laying her first and second eggs. The majority of the foreign eggs were the first or second eggs produced by the non-attendant female, i.e. they were not laying their entire clutch in other birds' nests. One hypothesis explaining the evolution and maintenance of pre-hatch brood amalgamation in birds is egg adoption by nesting females. This hypothesis appears to be the most likely mechanism in explaining the prevalence of foreign eggs in this population. In nests where a foreign egg was laid, before, or on the same day, as the attendant female initiated her clutch, the probability that the attendant females' first egg successfully reached incubation were significantly higher than in nests which did not contain foreign eggs. There is a high rate of partial clutch predation of first and second laid eggs, since nesting females do not attend their clutch until their second or third laid egg. Egg formation is most likely limiting clutch size in eiders, as there are no subsequent costs to incubating or raising extra young. I propose that female eiders perceive nest sites that contain foreign eggs as good quality (low predation risk) nest sites and in the process of choosing these nest sites adopt the foreign eggs at no cost to themselves.

Status of the common eider (Somateria mollissima) in New Brunswick.
MAWHINNEY, KIM. Atlantic Cooperative Wildlife Ecology Research Network, University of New Brunswick, Fredericton, New Brunswick E3B 6E1
DIAMOND, A.W. Atlantic Cooperative Wildlife Ecology Research Network, University of New Brunswick, Fredericton, New Brunswick E3B 6E1

In 1995 we conducted a pilot study of brood ecology of the Common Eider Somateria mollissima with specific reference to movements, habitat use and behaviour of both adult females and ducklings on the Wolves Archipelago in the Bay of Fundy. Information generated from this colony, particularly recruitment, over the next 3 years was to be used in conjunction with information collected from other breeding colonies to develop a model of the role of post-hatch ecology in the demographics of Common Eiders in the Bay of Fundy. Exceptionally high depredation rates by Great Black-backed Gulls Larus marinus on Eider ducklings precluded the study of brood amalgamation as only 12 of 3000 ducklings produced in this colony fledged. In 1996 breeding pairs of Great Black-backed Gulls were eliminated on two of the five islands in the Archipelago and clutches were prevented from hatching on two other islands. Great Black-backed Gulls on clutches that were oiled to prevent hatch had a protracted incubation period, and the absence of chicks did not reduce adult Great Black-backed Gull depredation on Eider broods as only 8 ducklings fledged.Duckling mortality on the Wolves Archipelago exceeded 95% in both 1995 and 1996. Brood surveys suggested that low duckling production was not confined to the Wolves Archipelago; and that duckling production in the Bay of Fundy has declined considerably over the last decade despite stable numbers in breeding pairs. High duckling mortality is a common phenomenon in Eiders and survival of ducklings does not apparently regulate Common Eider population numbers; however, it may potentially limit the growth rate of the population. Although the numbers of Common Eiders breeding in New Brunswick appear stable, we cannot be complacent; low annual recruitment over periods of several years has been associated with gradual declines in breeding populations of Common Eiders elsewhere.

Mitochondrial DNA control region sequence variation in Common Eiders reveals extensive mixing of subspecies
Baker, Allan J. Centre for Biodiversity & Conservation Biology, Royal Ontario Museum, Toronto, Ontario, Canada M5S 2C6 Grapputo, Alessandro. Centre for Biodiversity & Conservation Biology, Royal Ontario Museum, Toronto, Ontario, Canada M5S 2C6 Dickson, Kathy. Canadian Wildlife Service, Hull, Quebec, Canada K1A0H3 Wendt, Stephen. Canadian Wildlife Service, Hull, Quebec, Canada K1A 0H3 Scribner, Kim. National Biological Service, US Department of the Interior, Anchorage, Alaska 99503
We sequenced a hypervariable 319 bp portion of the control region of mitochondrial DNA in five subspecies of Common Eiders (Somateria mollissima) and an outgroup sample of King Eiders (S. spectabilis). Variation was found at 71 sites (22%), which defined 56 haplotypes in the total sample. A genealogical tree relating the haplotypes revealed three major clades, but with the exception of Common Eiders (S. v-nigra) from Alaska, they did not correspond with putative subspecies identities. No geographic structuring was apparent, and the detection of an Alaskan genotype in one bird collected in Labrador suggests that long-distance dispersal occurs. A molecular clock calibrated for control region I suggests that the major clades have originated within the last 300,000 years or so, and that there has been mixing of historically separated populations as the Arctic was recolonized relatively recently. To independently test this hypothesis and to check for male-biased dispersal, we will report preliminary results from biparentally transmitted nuclear markers at microsatellite loci. Future work needs to bebased on samples collected on the breeding grounds to obviate problems with winter mixing of populations.

Baillie,S.R. and H. Milne.1982. The influence of female age on breeding in the Eider (Somateria mollissima). Bird Study 29:55-66

Bedard, J.and J. Munro. 1977. Brood and creche stability in the Common Eider of the St. Lawrence estuary. Behaviour 60:221-236.

Bent, A.C. 1925. Life Histories of North American Wild Fowl. Order: Anseres (Part II) U.S. Natl. Mus. Bull.130. Washinton D.C. 396pp.

Carthy, J.D. and D.R. Arthur (eds). 1968 The biological effects of oil pollution on littorial communities

Cottam, C. 1939. Food habits of North American diving ducks. U.S. Dep. Agric. Tech. Bull. 643. 143pp.


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