Description

The Fraser River begins high in the Rocky Mountains of Canada and 1300 kilometers later it spills into the Pacific Ocean near Vancouver in southwest British Columbia. The river’s wide delta attracts millions of migrating birds annually making the Fraser River estuary a premier bird habitat in Canada.

Several million shorebirds pass over the estuary each year in migration and tens of thousands remain in the winter. The mudflats on Roberts Bank in the centre of the estuary harbor the greatest number of shorebirds. Over 500,000 western sandpipers have been estimated to use the mudflat on a single day in spring migration. The mudflats are many kilometers wide during low tide. The mud teams with tiny invertebrates – in some places over 1000 invertebrates have been tallied in a 10 cm diameter core of mud. And on the surface, tiny diatoms and bacteria coat the mud in a greenish hue that western sandpiper dab from the surface with specialized tongues. In the marshes, dowitchers probe for marine worms and yellowlegs dart after small fish. On the sandflats, black-bellied plovers and dunlins pursue marine worms.

High tides push the birds towards the marsh edges and falcons that prey on them. Some dunlins form into tight bundled flocks making hunting difficult for falcons while others join black-bellied plovers in adjacent cultivated fields to seek out terrestrial insects and worms. No month goes by when shorebirds are not on the delta.