Yellow-billed Cuckoos, Red Knots Proposed for Endangered Listing

A federal decision could offer hope to a pair of imperiled bird species.

What could the western yellow-billed cuckoo, a river-loving songbird, and the rufa red knot, an East Coast shorebird, possibly have in common? Both are Audubon Priority Birds, and they’ve been in steep decline since the late 20th century, adversely affected by habitat degradation and declining food supplies. Climate change has taken its toll on each, too: Extended droughts have affected cuckoo habitat, while rising sea levels have damaged red knot feeding grounds. But now, after years of intensive monitoring by Audubon and many partner organizations, there’s a glimmer of hope on the horizon for these birds.

In early October the U.S. Fish and Wildlife Service proposed listing the birds as threatened under the Endangered Species Act; a final decision is anticipated next summer. If the verdict favors the birds, the resulting habitat protection could give them a greater chance at rebounding.

Endangered species listing isn’t always the most effective strategy, and Audubon and other conservation favor using it judiciously. In the case of the greater sage-grouse, for instance, Audubon and its partners figured—correctly, as it turned out—that working with government agencies and private landowners would be the most effective way to conserve the species. With the yellow-billed cuckoo and the rufa red knot, however, listing could be the last, best hope.

Editorial Note: The FWS is currently accepting public comments. Anyone who wants to voice their support for listing the birds can do so through Audubon’s Action Center. Click here for the western yellow-billed cuckoo; the deadline is December 2. Click here for the rufa red knot; the deadline is November 29.


Western yellow-billed cuckoo

This slender bird has always been incredibly difficult to find in the wild, where they often perch on tree branches, still as statues, their white underbellies blending in with the foliage as they wait to snatch up unsuspecting caterpillars. Yellow-billed cuckoos are easiest to spot by the bold white circles under their tail feathers, though another option for tracking them down is to listen for their loud call—especially if you’re willing to brave rough weather. They emit an elaborate, croaking noise, especially at the onset of thunderstorms, which has led to their nickname, the “raincrow.”

But now yellow-billed cuckoos are even harder to find. Once abundant throughout the West, the species declined exponentially in recent decades. “California, for example, had 15,000 pairs of cuckoo around the 1900s, but 30 pairs by 2000. That’s kind of stunning, isn’t it?” says Tice Supplee, Audubon Arizona’s director of bird conservation. 

Because they live only in the Southwest’s riparian forests, dams and waterway diversions have severely altered their homes. Long droughts certainly haven’t helped either. “Ninety percent of our riparian habitat is either altered or destroyed, and the cuckoo’s decline appears to coincide with that number,” says Supplee. Now the cuckoo is limited to Arizona, California, New Mexico, and small areas around the Rio Grande in Texas. “We feel strongly that if action were taken to conserve and protect riparian habitats, we could turn things around.”

Gaining protection for this bird has been an arduous, 15-year process, says Supplee. In 2005 the USFWS actually considered listing the cuckoo under the Endangered Species Act. But “it was of lower priority than other species, so it was put on the back burner,” Supplee says. In response, the Center for Biological Diversity sued the federal government in a case where multiple species were ultimately put on a court-ordered timetable for listing.


Rufa subspecies of the red knot

The red knot, a rust-colored shorebird, is arguably most renowned for its 9,000-mile biannual migration   one of the longest of any bird. During this journey from Arctic nesting grounds to Tierra del Fuego for wintering, dense groups stop along the Atlantic Flyway and feast on horseshoe crab eggs to fuel their remarkable flight. 

In fact, red knots depend so heavily on the eggs that their spring migration is timed with horseshoe crab spawning along the United States’ southeastern and mid-Atlantic coast. “These eggs are a very rich food item for them and it helps them tack on enough fat to replenish fat reserves lost during migration” says Walker Golder, deputy director of Audubon North Carolina. “The breeding season is short and it’s a real energy demanding endeavor, so they really have to arrive at breeding areas in great nesting conditions.” Commercial harvesting of horseshoe crabs along the Atlantic Coastparticularly in Delaware Bay, a crucial stopover site    seem to directly correlate to population decline, particularly in the past 20 years. Since the 1980s red knot populations have fallen by 75 percent.

Shoreline alteration along the Atlantic Coast is also taking a toll on these birds. Dredging, erosion, and the installation of erosion control structures, for example, affect the rest of the red knot’s food supply, including clams, mole crabs, and small snails. “When you have all of these problems stacking up against the birds, it’s no wonder their population is declining,” says Golder.

Populations seem to have stabilized after years of plummeting, though the numbers are still extremely low. Listing is a step in the right direction, says Golder, to get the birds back on track.

Listing both the cuckoo and the red knot as ‘threatened’ will ensure that their populations are closely monitored and that habitat protections are put in place. A final verdict for each species is expected next summer.