Land along the southern shores of British Columbia’s Strait of Georgia is at a premium — not only to developers eager to capitalize on access to ocean ports, fertile farmland and stunning views, but also to millions of migrating birds that pause to feed en route to and from their breeding grounds up North. With the human population of the area growing rapidly — and now topping three million — these birds are being caught in a potentially devastating squeeze play.
One of the area’s smallest visitors is the Western Sandpiper, a sparrow-sized shorebird that nests in Alaska and migrates primarily along the Pacific flyway to extensive coastal wintering grounds between the southern United States and Peru. Biologists have long known that “peeps” — the generic term for small shorebirds — feed on bite-sized invertebrates in and on intertidal mudflats. One such mudflat is Roberts Bank, located on the Fraser River delta just north of the international border. The Bank teems with crustaceans, molluscs and other edibles, providing prey for a wide variety of birds, including millions of Western Sandpipers.
What was not known, until recently, is that there are other ways Western Sandpipers feed, and what they feed upon is more precisely tuned to particular conditions on the Bank than was originally thought. Scientists at Environment Canada’s Canadian Wildlife Service and the Université de Nantes in France discovered, through the use of scanning electron microscopy, that the bird’s bill and tongue contain structures that enable the bird to detect and slurp up “biofilm” — a micro-thin layer on surface mud that contains bacteria, algae, small crustaceans and their mucus excretions. This feeding method likely uses mucus on the bird’s tongue to adhere to mucus in the mud, and the tip of its bill to sheer off gobs of the nutritious goo. Although other species of birds sift through mud to get food, it had never been appreciated that some might actually ingest this material itself. Other field observations and experiments involving researchers at the University of British Columbia and Simon Fraser University have shown that Western Sandpipers also find large worms in the mud by homing in on the pressure waves they produce.
Like most of the shoreline along the Strait of Georgia, Roberts Bank has seen significant reduction, disruption and pollution from coastal development over the past four decades. Yet, despite the fact that it is an internationally important bird habitat, the Bank is currently under no legal protection as a wildlife area. It is home to giant ferry and port terminals that service thousands of ships per year — each vessel carrying fuel, oil and other products that could have devastating impacts if they were spilled. As a surface feeder, the Western Sandpiper is particularly susceptible to heavy metals and other pollutants from industrial sources.
The Bank has also been affected by the construction of two large human-made causeways that support the ferry and port terminals. These have blocked the natural flow of nutrients from the Fraser River onto the Bank, and thereby altered the invertebrate communities and disrupted the biofilm. Hence, mudflat feeders, such as the Western Sandpiper, seem to have been pushed into a much-reduced area. The future of the Bank is further threatened by the fact that 700 hectares of agricultural land along its shore are now the subject of development proposals that could have significant environmental impacts on the mudflats.
Teams of biologists from Environment Canada and local universities are continuing to study the Western Sandpiper and its habits in an effort to learn more about conserving the species in the Fraser Delta, and to ensure that steps are taken to protect its vital habitat — before human development squeezes it out.
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