IBA Somenos Marsh Wildlife Refuge
Duncan, British Columbia
Site Summary
BC051 Latitude
Longitude
48.801° N
123.699° W
Elevation
Size
4.5 - 7.5 m
5.70 km²
Habitats:
mixed woods (temperate), scrub/shrub, rivers/streams, freshwater lake, freshwater marsh, arable & cultivated lands
Land Use:
Agriculture, Nature conservation and research, Fisheries/aquaculture, Tourism/recreation
Potential or ongoing Threats:
Agricultural pollution/pesticides, Dredging/canalization, Filling in of wetlands, Introduced species, Urban/industrial development
IBA Criteria: Globally Significant: Congregatory Species, Nationally Significant: Threatened Species
Conservation status: Nature Trust of British Columbia, Wildlife Refuge (provincial)
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Site Description
Somenos Marsh is located in southeastern Vancouver Island, a short distance north of downtown Duncan. The marsh system is 200 hectares in size, and includes Somenos Lake and four creeks. Grass and shrub habitats are common, and willows are interspersed throughout. The farmlands become flooded marsh-like areas in winter and spring. Water levels can rise as much as 2.5 m in winter. Some of the rare flora and fauna found here include the Vancouver Island Ringlet, Prairie Lupine, Yellow Montane Violet, and Garry Oaks growing in deep soils. The IBA includes the wildlife refuge and a heronry that is on the west side of the Trans Canada Highway.
Birds
Somenos Lake is known for the high number of Trumpeter Swans that over-winter each year. Christmas Bird Count data show that up to 1,000 birds can be present roosting and feeding in the lake and flooded wetlands. This represents about 5% of the worlds population of Trumpeter Swans, and is the second largest over-wintering number of Trumpeter Swans on Vancouver Island. In the first half of the 1990s, typically about 600 Trumpeter Swans wintered in the marsh and lake. But, because the Trumpeter Swan population has been increasing in recent years, more birds have been seen since then. Also, just over 1% (25 pairs) of the Canadian population of the nationally vulnerable fannini subspecies of the Great Blue Heron breed and winter here. The actual nesting site is on the west side of the Trans Canada Highway, although the birds feed in the lake and marsh. Somenos Lake is a good spring, fall and winter location for waterfowl. During the winter, there are concentrations of up to 2,000 waterfowl on the lake and surrounding fields. In addition, two pairs of Barn Owls nest in the area; the British Columbia population of this species is nationally vulnerable. Two hundred and nineteen species have been recorded in the refuge in total including passing rarities such as Tufted Duck, Eurasian Wigeon, Black-crowned Night-Heron, White-faced Ibis, Great Egret and Black-throated Sparrow.



IBA Criteria
SpeciesT | A | I Links Date Season Number G C N
Great Blue Heron 1998 SU 50
Trumpeter Swan 1997 - 1998 WI 607 - 1,000
Western Screech-Owl 2007 SP 1
Note: species shown in bold indicate that the maximum number exceeds at least one of the IBA thresholds (sub-regional, regional or global). The site may still not qualify for that level of IBA if the maximum number reflects an exceptional or historical occurrence.
 
Conservation Issues
Since it formed in 1989, the Somenos Marsh Wildlife Society has worked to protect the marsh. To date they have facilitated acquisition of parts of the conservation area by the Nature Trust of BC, and have assisted Ducks Unlimited in the ongoing (since 1994) process of acquiring Somenos Lake. The society has created a steering committee to look at joint management of the Somenos properties. Also, recent activities of the society include: the removal of asphalt and site restoration work at the edge of the marsh; work to reduce flooding to allow for haying (and the growth of fewer willows) which would improve waterfowl habitat; stream assessment and restoration; construction of new dock and viewing platform in Somenos Lake; and the building of bird blinds, bird boxes and concealed boardwalks.

The IBA Program is an international conservation initiative coordinated by BirdLife International. The Canadian co-partners for the IBA Program are Bird Studies Canada and Nature Canada.
   © Bird Studies Canada