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Estuarine Habitat Critical for Shorebirds

Least Sandpiper 512x360Where human beings see a desolate mudflats, shorebirds see a restaurant.  In fact, no other habitat is able to sustain shorebirds on their seasonal migrations north and south along the coast, making the conservation of this habitat critical for the survival of most shorebird species.

When a person first takes an interest in birds, they might start with the common birds that turn up at the backyard birdfeeder. During a first foray to a wild land, the easy-to-see waterfowl or flashy warblers are a common first target. If a bird isn’t colorful or if it doesn’t sing, then what’s the point? When asked for the first time about shorebirds, a new birder might scratch their head and think, “What’s that?” They are small and brown. They don’t sing. They are notoriously hard to identify.

Weighing in at about one ounce, the least among them is undeniably the Least Sandpiper. Their tiny size is perhaps their defining characteristic; they have yellow legs, but these can often be mud-stained and hard to see. Otherwise, the Least Sandpipers are best identified by what they are not. They lack the long, dropping bill of a Dunlin; they lack the long neck of a pectoral or spotted sandpiper; the back of a Western Sandpiper is typically more strikingly speckled with rufous highlights. The Semipalmated, Baird’s, and Least sandpipers would look nearly identical were it not for the Least’s yellow legs … And so it is that many beginning birders, initially enthusiastic, choose to skip shorebirds and move on to something else, something easier …

But Least Sandpipers, and the larger family of shorebirds, are significant. They represent an evolutionary paradox: their success comes from their special adaptation to a specific habitat, and this also is what makes them most vulnerable. The shape of a shorebirds bill is adapted to feeding very specifically on the invertebrates that live in the sand or mud on shorelines. In the case of the Least Sandpiper, the bill is best suited to the mud found in estuaries and marshland – not on beach sand. Mud additionally matters most to the Least because, unlike any other type of shorebird, they use the surface tension of water to deliver food from the tips of their beaks to their mouth. Where there is no water-saturated mud, there can be no Least Sandpipers. In this way, they are intimately connected to estuary habitat like that found at Grays Harbor and at Nisqually National Wildlife Refuge.

Until modern times, the special adaptations of shorebirds like the Least meant exclusive access to a cornucopia of food. No other category of bird could make use of mudflats, marshland, and shorelines. The abundance of food supported an enormous population of birds. In a mesmerizing spectacle, these enormous populations migrate up and down the coasts in transcontinental migrations no longer seen elsewhere in the animal kingdom. But their migration is delicate and vulnerable, fueled as it is by the bounty of estuarine habitat.

As human populations have grown, urbanization has led to wetland degradation and destruction, robbing shorebirds of their only food source during migration when food is most critical. Predictably, those shorebird populations utilizing flyways where the most habitat has been lost to urban expansion are the same populations most in decline. But flyways where the habitat has, so far, been left largely intact are no less fragile than those in decline, so with this understanding, remaining estuaries like Grays Harbor have been recognized as valuable and worthy of protection; others, like Nisqually, are being restored. A visit to these refuges during the Spring and Fall migrations offers a glimpse back in time to the era of mass migrations. You can see this spectacle and learn more about shorebirds, including the Least Sandpiper, at this year’s Shorebird Festival, which will be held April 25-27 at Grays Harbor National Wildlife Refuge.

Page Photo Credits — least sandpipers, Michael Schramm/USFWS
Last Updated: Mar 14, 2014
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