Natural history: Dunlins in Blaine and Birch Bay

The upcoming Wings Over Water Northwest Birding Festival (March 17-19) reminds me to watch for dunlins on the mudflats around Blaine and Birch Bay. When actively feeding, these medium-sized shorebirds in the sandpiper family methodically probe the mud for marine worms, small shellfish and other invertebrates. This probing is done with a long, thick bill that bends slightly downward. 

One of the largest concentrations of birds I have ever seen consisted of tens of thousands of dunlins in Boundary Bay, about five miles north of the U.S./Canada border. They were all earnestly feeding, and it seemed like the tidal flats were in motion. 

I traveled to coastal tundra areas along the Chukchi Sea and Beaufort Sea coasts in Alaska to conduct wetland studies for about 12 summers. While doing this work, I would sometimes see dunlins in their prime nesting habitat. I recall having to watch my step because the dunlins and other shorebirds had ground nests well-hidden in the sedges, grass and dwarf shrubs.

Male dunlins typically arrive at the breeding grounds before the females and establish nesting territories on the treeless tundra. The female makes the final selection of the nest site. Dunlins are mostly monogamous, and both the male and female incubate the eggs and defend the nest site from predators. Predators include arctic foxes, weasels and ravens. The average lifespan of a dunlin is about 5.5 years.

Jonathan Hall resides in Birch Bay. He is a retired biologist who has worked in many regions of the U.S. while employed with the State of New York, the U.S. Fish and Wildlife Service, several environmental consulting firms and the Tulalip Tribes of Washington.