Tofino birdwatching: The Black Oystercatcher

by Lisa Fletcher, Tofino

You may have seen them, barely, blended in to the rocky coast. And if you've gotten close enough to hear them, you'd know their unmistakable squeak, just like a stuffed toy. Black Oystercatchers (Haematopus bachmani), are common year round residents along the rocky Pacific shoreline, from southern Alaska to Baja California. They are very distinct marine birds; a dark body, comical pink feet, bright yellow eyes, and a vibrant orange bill. The total population is less than 11,000 birds, with over 50% residing in Alaska, and 30% of the breeding population residing here on the West Coast of Vancouver Island. Some consider them to be one of the rarest shorebirds in North America.

They prefer to live on non-forested islands and rocky shorelines. You don't usually find them on the beach but rather on the rocky headlands or islets not far from shore. Black oystercatchers are completely dependent on the intertidal zones for their life requirements. They feed regularly on intertidal marine invertebrates, such as mussels, clams, limpets, and chiton, but are also known to feed on crab, urchins, and barnacles. Despite their name, oystercatchers are rarely seen feeding on oysters! They use their flattened scissor-like bill to slice the adductor muscle of slightly open mussels and remove the soft parts with its bill tip, or to easily pry chitons and limpets off of rocks.

During the winter, the birds are thought to congregate to protected tidal flats, although little is known about where. At age 4 or 5, oystercatchers begin to breed. Breeding season begins around May and usually lasts until July. These monogamous birds will establish and occupy the same feeding and nesting territories year after year. They tend to nest on rocky islets with gently sloping beaches of shell and gravel and with adequate foraging areas near the intertidal zone. The nest is made of shell fragments or pebbles that forms a hardly- even-noticeable bowl or depression. The male builds the nest, but he builds more than one so that the female can choose which one she wants to use (its always nice to have options!). The females lay from 1 to 3 eggs and both males and females take turns sitting on the nest for 26-30 days. The eggs are inconspicuously camouflaged, with an army green background and scrawled black spots. If a nest is disturbed or predators take the eggs, the female can lay more eggs (replacement clutch), up to three separate times. The chicks are downy at birth and are mobile fairly quickly but can't fly until 5 weeks old.

The oystercatchers year round dependence on such a narrow band of habitat and their small population size makes these birds particularly vulnerable to both natural and human disturbances. Some common predators include mink, river otters, gulls, ravens and eagles.

Human disturbance is thought to be one of the greatest threats to the breeding black oystercatcher. Disturbance such as campers, kayakers, and dogs often prevent pairs from breeding, or causes them to abandon their nest sites completely. Other indirect human disturbances that affect the oystercatcher are water contamination through oil spills or non-point source pollution. Even global warming-yes it's real- is thought to affect these birds with rising sea levels, greater coastal storm fluctuations and tidal surges. All of these factors have caused the Black Oystercatcher to be listed as a species of high concern by federal and state agencies and conservation organizations in the U.S. and Canada. The Pacific Rim National Park has been monitoring these birds for many years in Barkley Sound. Other monitoring programs have been developed all along the coast as well, in hopes of understanding more about these birds.

So the next time you are out exploring our amazing coastline, keep an eye out for the Black Oystercatcher, try not to get too close, and watch where you step!

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Lisa Fletcher is finishing her last year of her biology degree and is a fervent believer in evolution and revolution.