Conservation status: Ducks Unlimited Canada (owned by), Migratory Bird Sanctuary (federal), Nature Trust of British Columbia, National Wildlife Area (federal), Provincial Wildlife Management Area, Ramsar Site (Wetland of International Significance), Regional Park (provincial), Western Hemisphere Shorebird Reserve Network
The Boundary Bay - Roberts Bank - Sturgeon Bank site (Fraser River Estuary) is a large complex of interconnected marine, estuarine, freshwater and agricultural habitats in southwestern British Columbia near the city of Vancouver. It includes Boundary Bay, a predominantly marine ecosystem, the estuarine waters of Sturgeon Bank, between the north and south arms of the Fraser River, and Roberts Bank, south of the south arm of the Fraser River. Maritime habitats in the IBA include sand and mud flats, eelgrass, salt marshes, estuarine marshes with sedge, cattails and bulrush and deeper tidal waters. Agricultural habitats within the IBA include the fertile, deltaic farmlands of Richmond, Delta, and south Surrey, which provide important habitat for waterfowl, shorebirds and birds of prey. Patches of forest, including mature coastal Douglas fir, provide important nesting and roosting habitat for Great Blue Herons and raptors, including Bald Eagles. The network of rivers (Fraser, Serpentine, Nicomekl and Little Campbell) and associated wetlands within the site provided historical as well as current and potential future habitat for waterbirds. Burns Bog, lying in the heart of the delta, is a sphagnum moss wetland surrounded by shore pine and alder forest.
Boundary Bay, Roberts Bank and Sturgeon Bank form one of the richest and most important ecosystems for migrant and wintering waterbirds in Canada. This IBA supports globally or continentally significant populations of fifteen species, including American Wigeon, Northern Pintail, Mallard, Brant, Snow Goose, Trumpeter Swan, Western Sandpiper, Black-bellied Plover, Dunlin, Great Blue Heron, Western Grebe, Red-necked Grebe, Glaucous-winged Gull, Thayer's Gull, and Mew Gull. In addition, the IBA supports nationally significant numbers of Barn Owl and Peregrine Falcon.
In total, fifty species of shorebirds have been recorded in the area. The most numerous species found here is the Western Sandpiper - one-day, peak count estimates of at least 500,000 have historically (pre-2001) occurred during spring migration, though more recent estimates range from 120,000-180,000, which is a substantial proportion of the global Western Sandpiper population. Western Sandpiper also pass through on fall migration. Dunlin also occur in large numbers - one-day, peak counts in the spring exceeded 100,000 in 2004 and typically range from 26,000-85,000 birds. Large numbers of Dunlin can occur during fall migration and also overwinter in the delta. Black-bellied Plovers occur during winter and on migration, with one day counts of up to 6,000 birds. Dunlin and Black-bellied Plovers use both agricultural and estuarine habitats.
A significant proportion of the Wrangel Island Snow Goose population uses the banks; up to 38,400 regularly winter here; high numbers also occur on passage in fall and spring. The numbers of Snow Geese using the banks change significantly even within one winter because the birds move back and forth to the nearby Skagit River Delta in Washington State. Counts of 60,000 for the entire Fraser-Skagit Delta population are not uncommon between late October and March; about 100,000 birds were counted in 2007. During the fall and early winter, one-day counts of greater than 100,000 dabbling and diving ducks are made regularly in the IBA for species such as American Wigeon (up to 51,000), Northern Pintail (up to 44,000), Mallard (up to 27,000) and Green-winged Teal. Surf Scoters occur in large numbers in marine waters during the winter and in spring (typically 1,000-8,000 individuals); with populations exceeding global IBA thresholds twice since 2001. Many dabbling ducks use the agricultural lands and estuarine habitats.
Significant numbers of Trumpeter Swans winter in the IBA (up to 1,455 in 2010). Brant winter in marine waters of the IBA (4,080 in 2010) and pass through on spring migration. Most are Black Brant (Branta bernicla nigricans). In recent years, about 200 Western High Arctic, or Grey-bellied Geese have been present in winter. During the late summer and early fall, the area is also very important for moulting grebes. Historically, between 2,000 and 3,000 Western Grebes were regularly present in Boundary Bay, and a separate study reported over 2,000 on the estuarine banks (Stout and Cooke 2003, Butler and Cannings 1989). In recent years, Western Grebes have declined steeply; counts since 2003 have ranged from 200-1000 individuals and no longer exceed IBA thresholds. This significant decline has been noted throughout the Salish Sea (in British Columbia and Washington); the reasons for the decline are not clear and are under investigation (Wilson et al. 2013). Red-necked Grebes are also present in the IBA during spring and fall migration and winter; counts have exceeded IBA thresholds in four years since 2001, with a peak count of 2,716 in 2002.
Glaucous-winged Gulls are present year-round and occur in significant numbers during the winter, with a peak count exceeding 55,000 in 2006. Large numbers feed at the Vancouver Landfill in Burns Bog and roost on surrounding fields and on marine waters of Boundary Bay, Roberts and Sturgeon Banks. Significant numbers of Mew Gulls are also present in the fall (counts up to 1,217 in 2007) and winter (up to 3,770 in 2005). Thayer's Gull occurs in significant numbers in the winter as well, with up to 623 counted in 2001.
The IBA supports important numbers of three species determined to be Threatened or Special Concern by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC; wildlife species that have been assessed as at risk by COSEWIC may qualify for legal protection and recovery under Canada's Species at Risk Act). Great Blue Heron (A.h. fannini subspecies) (Special Concern, COSEWIC) has several colonies in the IBA, including a very large one on a forested bluff adjacent to Roberts Bank and the Tsawwassen ferry jetty, with about 250-450 nests (Welstead, pers comm.). These herons are resident, and feed in intertidal areas during the breeding season, as well as on farmland, especially in winter. Barn Owl (Threatened, COSEWIC) nest in and around farmlands within the IBA; up to 106 nest sites were active over six years from 2006-2012 (Hindmarch, pers comm.). Peregrine Falcon (Special Concern, COSEWIC) regularly occurs during the winter. The number of Bald Eagles using the IBA in the winter has also increased in recent years and may exceed IBA thresholds in the future.
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.
The major, immediate threat to the ecological integrity of this IBA is permanent loss, degradation (loss in quality) and fragmentation of habitats. The IBA overlaps Canada's third largest urban centre, Metro Vancouver, supporting a population projected to grow by 1.4 million by 2040, and the largest port on North America's west coast, Port Metro Vancouver, on which the region's economy is founded. Agricultural, estuarine and marine habitats have been, and continue to be lost and fragmented by current and proposed urban developments (e.g. the Southlands adjacent to Boundary Bay and Tsawwassen First Nation lands adjacent to Roberts Bank), industrial developments (e.g. major expansion of Port Metro Vancouver on Roberts Bank and adjacent upland), and related transportation and infrastructure developments (e.g. jetties, causeways, highways, bridges, rail yards, airports). Conversion of open agricultural fields to berry crops, greenhouses and other intensive uses has reduced farmland habitat available to waterfowl, shorebirds and owls (e.g. Barn Owl).
Terrestrial and aquatic habitat quality is reduced by runoff from urban, industrial and agricultural activities (Swains and Holms 1988) and dumping of contaminated water, although long-term and cumulative effects are poorly understood. Concerns about contamination from ballast water are lessened as long as de-ballasting takes place mid ocean as required. The risk of marine spills, including oil, will increase with proposed increases in shipping traffic to meet trade demands.
Changes in the marine food chain appear to be impacting some bird species. Forage fish, such as herring and sand lance, have declined in the Salish Sea in recent years, and a corresponding decrease in diving birds that predate on forage fish has been observed (Crewe et al. 2012, Anderson et al. 2009, Therriault et al. 2009).
A variety of introduced species present potential local and ecosystem level concerns. Exotic mollusks are common in intertidal areas, including Batillaria snail, Venerupis philippinarum (manila clam), and Nuttalia obscurata (purple varnish clam). Zostera japonica (exotic eelgrass) is present on Roberts Bank and in Boundary Bay. Spartina anglica (exotic cordgrass) is proving extremely difficult to control and has the potential to change intertidal mudflat to unproductive grassland (Knight 2012).
Direct mortality through fisheries by-catch (Hamel et al. 2009, BC Coast BirdWatch 2011), collisions or overhead transmission wires (Burger and Cassidy 1995), and illegal hunting (Environment Canada 2011) may have cumulative impacts on trigger species populations. Mitigation measures implemented on transmission wires have had some success, but have not eliminated collisions entirely (Cassidy et al 1998).
Widespread recreational disturbance, including hunting, dogs off leash, kite-boarding in shallow intertidal waters, and power boating in sensitive marine near shore habitats, causes migratory birds to re-distribute. The long term impacts of these disturbances are not known and need to be quantified.
Potential impacts of cumulative air and light pollution have not been studied.
Conservation management areas provide a degree of protection across approximately 45% of the IBA, mostly in the inter- and sub-tidal habitats. Alaksen National Wildlife Area (including Reifel Migratory Bird Sanctuary) and provincial Wildlife Management Areas (WMAs), including South Arm Marshes, Boundary Bay, Sturgeon Bank, Serpentine, and Roberts Bank WMAs, cover almost 40% of the IBA. The management plans for all WMAs except the Serpentine WMA need to be updated. Several regional and local parks include important mudflats and marsh habitats along the shore (e.g. Boundary Bay Regional Park and dyke trail, Mud Bay Park, Blackie Spit). Ducks Unlimited and The Nature Trust of BC own and manage important agricultural and intertidal land parcels, and 2,400 ha of Burns Bog have been designated as an Ecological Conservancy Area.
Much of the farmland within the IBA falls within the BC Agricultural Land Reserve, established to preserve agricultural land and encourage the establishment and maintenance of farms as a secure source of food. The Delta Farmland and Wildlife Trust coordinates stewardship programs that benefit farming and wildlife on over 1,400 ha of active farmland within the IBA.
The importance of the Fraser River Estuary is recognized through several other international designations. The Fraser River Estuary IBA was designated a Hemispheric Site under the Western Hemisphere Shorebird Reserve Network (WHSRN) in 2004. The Alaksen National Wildlife Area was originally designated as a Ramsar Wetland of International Significance in 1982. In 2012, this site was expanded from 586 to 20,682 ha, capturing Burns Bog, Sturgeon Bank, South Arm Marshes, Boundary Bay, and the Serpentine, and renamed the Fraser River Delta Ramsar Site. Roberts Bank Wildlife Management Area remains to be included in this Ramsar designation.