My first opportunity to appreciate the diversity and sheer numbers of waterbirds in the vicinity of the Fraser River Estuary was from the back of a boat. After a couple of rather unsettling hours of heavy rain and rolling seas, the weather opened and we were treated to close views of rafts of Surf Scoters (Melanitta perspicillata), with loons and auks scattered in every direction, and a memorable northbound “stream” of Bonaparte’s Gulls (Chroicocephalus philadelphia), the new spring sunshine catching their fresh breeding plumage.
A big flock of Shorebirds on Roberts Bank. Photo: Tom Middleton
In May 2011, Jim Chu (of US Forest Service) and I had joined Rob Butler (at the time with Birds Canada) to spend a few days learning about how shorebirds use the Fraser River Estuary on their northbound migration to Arctic breeding grounds. To do so, I took a similar path as a northbound Western Sandpiper (Calidris mauri). The first stop on my journey north had been the Upper Bay of Panama, the winter home for perhaps one third of the global population of Western Sandpiper. Next was San Francisco Bay, where a delay in the plane landing gave me ample opportunity to appreciate from the air the expanse of the bay’s intertidal mudflats and salt ponds, home to more wintering Western Sandpipers, and larger numbers on northward migration.
In Seattle, I met up with Jim, and we visited the Greater Skagit and Stillaguamish Delta to learn about how restoration efforts for federally-listed salmon species are also benefiting shorebirds, including Western Sandpipers. We then moved on to the Fraser River Estuary. The day after the boat trip, we visited Brunswick Point, my first chance to see shorebirds on Roberts Bank. Growing up on the south coast of the UK and being a regular participant in shorebird counts from age 12 onwards, I thought I knew what large flocks of shorebirds looked like. But seeing 190,000 Western Sandpipers and Dunlin (Calidris alpina) congregated by the rising tide was an extraordinary experience, opening my eyes in more ways than one.
WHSRN sign on the Fraser River Estuary in British Columbia, Canada. Photo: Pete Davidson
This extraordinary experience for me, was an ordinary experience for Rob Butler. He knew we would find these shorebirds at Roberts Bank. Research shows that the mudflats of Roberts Bank have the specific ecological conditions that create the exact composition of biofilm required to enable production of the fatty acids that hundreds of thousands of shorebirds require on their migration. Biofilm is a critical nutrition source for migrating Western Sandpipers and other mudflats in the Fraser River Estuary do not enable such extensive, optimal fatty acid production conditions.
Jim and I continued our journey north, mirroring that of the Western Sandpipers. We stopped at Wrangell, Alaska, where a short boat trip took us to a hidden arm of the Stikine River Delta, where just one small area held over 20,000 Western Sandpipers and Dunlin. The final stop on our journey was the Copper River Delta. This is also the final migration stop for many of the Western Sandpipers, Dunlin and other shorebirds (5 million birds) we’d seen along our journey, before they head to their nesting grounds in the Alaskan tundra and boreal forest.
The Fraser River Estuary is a critical link in this chain of key sites for shorebirds, stretching from the Arctic tundra to the mangrove-fringed mudflats of Central and South America. Quite possibly almost the entire world population of Western Sandpiper is dependent on the intertidal mudflats of the estuary for refueling during migration. I’ve had several other opportunities to visit the Fraser River Estuary and appreciate the wildlife spectacle that it supports. During one visit in the depths of winter, shorebirds were notable by their absence, but arable fields just inland from the mudflats were being quartered by Northern Harriers (Circus hudsonius) and Short-eared Owls (Asio flammeus) – more in one place than I’d ever seen before. Enjoying the sight were over 50 bird photographers, each one with camera equipment worth more than some cars.
During my most recent visit, we stopped at the Iona Island Sewage Ponds in Richmond, famous (or infamous) for being the site of the only North American record of the charismatic Spoon-billed Sandpiper (Calidris pygmea) away from remote Alaskan islands. I was there with a colleague (who shall remain nameless) who is still pained by not having seen that bird, now 42 years later. He made the trip to see the bird, but arrived at the sewage ponds just after it had departed, after a multi-day stay. His pain is partly because Spoon-billed Sandpiper is unlikely to occur in British Colombia (or North America) again – the species is now perhaps the most threatened shorebird in the world (with a population of just a few hundred birds).
Left: Short-eared Owl. Photo: Yuri Chofour – Right: Thin layer of biofilm on mudflat at Roberts Bank. Photo: Laura Chamberlin.
The precipitous decline in the population of the Spoon-billed Sandpiper is largely due to the loss of intertidal habitats to development along its migration route in East Asia. Hopefully the critically endangered status of this species is not a harbinger of the future for shorebirds that are currently still numerous in the Americas. Many species are increasingly facing a similar threat of the loss of their coastal habitats, and shorebirds as a whole represent one of the groups suffering the greatest declines of any birds in North America.
Unfortunately, the intertidal habitat at Roberts Bank, where I witnessed nearly 200,000 Western Sandpipers and Dunlin, is at risk. The Vancouver Fraser Port Authority has proposed a large expansion of the Roberts Bank Terminal. The expansion will double the size of the existing artificial island and causeway, potentially creating irreversible changes to the flow of salt and freshwater across the mudflats. This change could alter the fatty acids of the biofilm and lead to species-level consequences for the Western Sandpiper and other shorebirds. When it comes to an ecosystem rich in the right kind of biofilm, at present we simply don’t know enough to make an irreversible change.
For more information, please contact James Casey jcasey@birdscanada.org
Cover Photo: Panoramic of Fraser River estuary with IBA and WHSRN signs.
