Keeping Clapper Rails High and Dry

Floating shelter/nest structure at Arrowhead Marsh in Oakland.

Photo courtesy USGS.

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Jan-Mar 2012

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by Juliet Grable — published February 16, 2012

The endangered California clapper rail has already suffered the loss of most of its wetland habitat and increased predation by nonnative mammals.

Now the rail faces a new threat: rising sea levels and extreme high tides that could flood out its high marsh refuges and leave it more vulnerable to predators.

In response, the Western Ecological Research Center (WERC), part of the U.S. Geological Survey, is testing the use of artificial floating "islands" as high-tide refugia for the rails.

In October 2010, researchers anchored ten of these "islands" in Oakland's Arrowhead Marsh. The structures, each about the size of a twin mattress, were constructed of recycled plastic and wrapped in a weave of palm leaves. The rails took to the floating sanctuaries almost instantly. Cameras mounted on the islands revealed that rails used the islands more than any other creature did, most frequently during high tides.

The islands may also help with nesting, keeping high tides from flooding nests or washing chicks away: To the researchers' delight, one pair of rails took advantage of the high and dry island to build a nest and fledge at least three chicks.

This winter WERC is reinstalling artificial islands in Arrowhead Marsh. "We want to verify that last year's results weren't a fluke," says Cory Overton, the biologist coordinating the project. Unusually wet weather spurred phenomenal plant growth at Arrowhead this year, which means more natural cover for the birds, but he says the shelters will still be important at high tide.

With funding from the U.S. Fish and Wildlife Service and the State Coastal Conservancy, Overton and his crew are also planning to add 25 smaller nesting islands in five marshes around the region during the spring breeding season. "We want to look at a range of marsh conditions with varying densities of birds," he says.