The Plight of the Yellow-Billed Cuckoo

cuckoo yellow
Western yellow-billed cuckoos require a riparian habitat.

Make the trees tall, thick and dense, let the water run free -- and the cuckoos will come.

That’s a big part of what the rare, potentially protected Western yellow-billed cuckoos needs in the way of living space, says a researcher who has studied the elusive birds for 20 years.

“They require native (riparian) habitat – cottonwoods and willows, tall trees, 15 to 40 feet tall,” said Matt Johnson, who works for Northern Arizona University and also has researched the cuckoo for the United States Geological Survey.

Also important is that the treetops have thick, dense canopy cover of tree foliage up high, said Johnson, director of NAU’s Colorado Plateau Research Station. This is important for many birds, not just cuckoos, to hide nests from predators, and to moderate daytime temperatures, shielding the birds from the brutal desert sun, said Christopher Calvo, a research biologist who works with Johnson at the Colorado Plateau station.

The U.S. Fish and Wildlife Service recently proposed to list the cuckoo as a threatened species, potentially triggering a suite of protective measures if the bird is listed – or a huge conflict pitting environmental interest groups against development and other business interests over whether it should be listed.

… From Johnson’s view, one of the biggest problems plaguing the cuckoos in the U.S. is that over the last three or four decades, the dams built during the 1950s, ‘60s and ‘70s across many Southwestern river corridors wiped out much of their historic cottonwood-willow breeding grounds.

Other main causes of riparian habitat loss are the conversion of these areas for farming and other uses, water diversion, stream channelization projects to straighten the rivers and livestock grazing, scientists have said. Groundwater pumping and non-native plant invasions have also taken their toll on streamside plant life.

“All these areas with dams just became a canal. They lowered the water table so low that the cottonwoods and willows can’t tap into it,” Johnson said.

Plus, it’s unknown what, if any problems the bird has encountered in its South American wintering grounds, Johnson said. They spend seven to eight months annually down there. But due to lack of research, researchers aren’t sure what habitat they occupy and how much other factors such as pesticides may affect the birds, he said.

. . . What researchers have learned is that habitat changes can clearly affect cuckoo populations. Because the Lower Colorado River, for instance, is an area that has been part of a federal habitat conservation plan, authorities have started restoring some of the river’s vanished cottonwood-willow stands over the past two decades.

Yellow-billed cuckoos have started breeding in those restoration sites in the past five to six years, including areas south of Cibola National Wildlife Refuge north of Yuma, Johnson said. The same phenomenon has occurred at the Palo Verde Ecological Reserve just north of Cibola and at the Ahakhav Tribal Preserve along the Lower Colorado outside the riverfront town of Parker, he said.

--excerpted from an article by Tony Davis in the Arizona Daily Star.