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Location Canada, British Columbia
Central coordinates 123o 7.26' West  49o 9.05' North
IBA criteria A4i, A4iii
Area 76,000 ha
Altitude 0 - 5m
Year of IBA assessment 2008

Bird Studies Canada/Nature Canada

Site description The Boundary Bay - Roberts Bank - Sturgeon Bank site is a large and complex area in southwestern British Columbia near the city of Vancouver. It includes Boundary Bay and the estuarine Sturgeon and Roberts banks, both of which are coastal wetlands and waters north and south respectively of the south arm of the Fraser River (which is also part of the site). Habitats found here include mudflats, and intertidal marshes predominantly composed of sedge, cattails and bullrush, which are critical to the Fraser River estuary ecosystem. The breakdown of detritus from marsh plants provides about 90% of the estuarine energy. The site also includes Point Roberts (USA) which separates the banks from the shallow Boundary Bay, Mud Bay and Semiahmoo Bay, all of which are more saline than the banks. At low tides, large mudflats form in the bays and extensive eelgrass beds are exposed. Finally, the fertile farmlands of Richmond, Delta, and south Surrey are part of this IBA. This site provides critical habitat for fish, such as the five salmon species, Herring, Coastal Cut-throat Trout and bottom fish species.

Key Biodiversity Boundary Bay, Roberts Bank and Sturgeon Bank form one of the richest and most important ecosystems for migrant and wintering waterbirds in Canada. The most numerous species found here is the Western Sandpiper there are one-day estimates of at least 500,000 during spring migration. Numerous species, including the Western Sandpiper, move from one part of this site to another; this is why these three areas have been amalgamated into one IBA. It is thought that a substantial proportion of the global Western Sandpiper population stops on the delta in the spring.

Dunlin occur in impressive numbers; one-day counts in the spring represent about 10% of the ssp. pacifica population, and 8% of the North American population. Large numbers of Black-bellied Plovers (one-day counts of as much as 3% of the estimated North American population) are recorded. Both Dunlin and Black-bellied Plovers winter in significant numbers. In total, fifty species of shorebirds have been seen in the area.

During the fall and early winter, one-day counts of greater than 100,000 waterfowl are made regularly. Some of the most abundant species include: American Wigeon (2% of the global population), Northern Pintail (1% of the North American population), Mallard (often occurs in numbers >20,000) and Green-winged Teal. Although not as numerous, significant numbers of Trumpeter Swans also winter, with a minimum of 4% of the Pacific Coast population being recorded. About 47% (or 46,700 birds) of the Wrangel Island Snow Goose population uses the banks. In the fall, one-day totals of 10,000 to 15,000 are more typical. In the spring, thousands of Brant (mostly ssp. nigricans) pass through the area. Numbers peak in April, with recent numbers typically between 1,250 and 3,300, or 1 to 2% of the Black Brant population. In the winter, smaller numbers of a different population are found; in recent winters about 200 Western High Arctic, or Grey-bellied Geese have been noted.

During the late summer and early fall, the area is also very important for moulting grebes. Between 2000 and 3000 Western Grebes are regularly present in Boundary Bay, and a separate study reports over 2,000 on the banks at a similar time of year. Thus, probably about 4% of the global population of the species is found here at this time of the year. Western Grebes have been recorded in significant numbers during the spring, fall and winter periods. As many as 2,500 Red-necked Grebes (about 5% of the estimated North American population) have also been recorded here in early fall. Large numbers of Glaucous-winged Gulls are present in the winter with an average of 19,000 gulls (from 1992 to 1997) being recorded (about 3.8% of the North Pacific population).

At least two nationally vulnerable species breed here. Three heronries of the Great Blue Heron ssp. fannini occur adjacent to Boundary Bay (at Point Roberts, Nicomekl River and Serpentine River). These colonies represent 6% of the total fannini population. These herons, and others presumably from colonies further away, feed in Boundary Bay and the banks throughout the year. The Fraser River delta also supports one of the last Canadian nesting populations of the nationally vulnerable Barn Owl. An average of 15 birds that were recorded on the 1992 to 1997 Ladner Christmas Bird Counts represents 1.5% of Canada's estimated population.

The marshes of Roberts and Sturgeon Banks support breeding American Bitterns, Soras, Virginia Rails, waterfowl and Northern Harriers, and outside the breeding season, large numbers of feeding swallows, Bald Eagles, Northern Harriers, and Peregrine Falcons. The area also supports large numbers of Short-eared Owls, Red-tailed Hawks and Rough-legged Hawks in the winter.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
Brent Goose Branta bernicla passage  1999  4,751 individuals  A4i  Least Concern 
Trumpeter Swan Cygnus buccinator winter  1995  526 individuals  A4i  Least Concern 
American Wigeon Mareca americana winter  1995  30,500 individuals  A4i  Least Concern 
Red-necked Grebe Podiceps grisegena passage  1998  2,576 individuals  A4i  Least Concern 
Western Grebe Aechmophorus occidentalis passage  1998  3,000 individuals  A4i  Least Concern 
Western Sandpiper Calidris mauri passage  1992  500,000 individuals  A4i  Least Concern 
Dunlin Calidris alpina winter  1995  29,000 individuals  A4i  Least Concern 
Glaucous-winged Gull Larus glaucescens winter  1995  19,000 individuals  A4i  Least Concern 
A4iii Species group - waterbirds winter  500,000-999,999 individuals  unknown  A4iii   

IBA Monitoring

2013 high not assessed low

Agriculture and aquaculture annual & perennial non-timber crops - agro-industry farming happening now some of area/population (10-49%) slow but significant deterioration medium
Human intrusions and disturbance recreational activities happening now some of area/population (10-49%) slow but significant deterioration medium
Pollution industrial & military effluents - type unknown/unrecorded happening now majority/most of area/population (50-90%) slow but significant deterioration high
Residential and commercial development commercial and industrial development happening now some of area/population (10-49%) moderate to rapid deterioration high
Transportation and service corridors shipping lanes happening now some of area/population (10-49%) moderate to rapid deterioration high

Some of site covered (10-49%)  No management plan exists but the management planning process has begun  The conservation measures needed for the site are being comprehensively and effectively implemented  low 

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Alaksen National Wildlife Area 299 protected area contained by site 360  
Alaksen Wetlands of International Importance (Ramsar) 586 protected area overlaps with site 1,000  
Boundary Bay Wildlife Management Area 12,191 protected area overlaps with site 11,000  
George C. Reifel Migratory Bird Sanctuary 648 protected area overlaps with site 400  
Peace Arch Provincial Park 9 protected area contained by site 8  


IUCN habitat Habitat detail Extent (% of site)
Forest Temperate coniferous forest; Temperate deciduous woods  -
Wetlands (inland) Estuarine waters; Freshwater marshes/swamps; Intertidal mud, sand or salt flats; Salt/brackish marshes  -
Sea Open sea  -
Artificial - terrestrial Arable land; Urban and industrial areas  -

Land use

Land-use Extent (% of site)
agriculture major
nature conservation and research minor
fisheries/aquaculture major
hunting major
tourism/recreation major
urban/industrial/transport minor

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Recommended citation  BirdLife International (2016) Important Bird and Biodiversity Area factsheet: Boundary Bay - Roberts Bank - Sturgeon Bank (Fraser River Estuary). Downloaded from on 25/10/2016

To provide new information to update this factsheet or to correct any errors, please email BirdLife