The U.S. Fish and Wildlife Service has proposed to list the western population segment of the yellow-billed cuckoo as a threatened species under the Endangered Species Act.
In the U.S., the western yellow-billed cuckoo is known to occur in Arizona, California, Colorado, Idaho, Nevada, New Mexico, Texas, Utah, Wyoming, Montana, Oregon, and Washington. Locally, it has been found along the San Juan River near the Four Corners.
"The western yellow-billed cuckoo is distinct from populations in the east and has different habitat requirements," said Jennifer Norris, field supervisor for the Fish and Wildlife Service. "Populations of western yellow-billed cuckoo, and their nesting habitat along rivers and streams, have been declining over the last few decades."
The Service is looking for information concerning the western yellow-billed cuckoo's biology and habitat, threats to the species, and current efforts to protect the bird.
The western yellow-billed cuckoo is a neotropical migrant bird that winters in South America and breeds in western North America. It is an insectivorous bird that lives in riparian woodlands.
"They eat the larger bugs and an occasional frog, so pesticides are a threat to the bird as well as habitat fragmentation," said Sarah Swenty, a USFW assistant field supervisor. "They have been declining in the West and are down to a couple of pairs in some areas."
Confirmed recordings in the Four Corners during the 1980s are associated with outbreaks of caterpillars in box elders. Reports of single yellow-billed cuckoos have come primarily from the Grand Junction area and Mesa County. They have been sighted in recent years along the Gunnison, Uncompahgre and Yampa Rivers and near Nucla. The Colorado Bird Breeding Atlas surveys show no record of yellow-billed cuckoos in southwest Colorado from 1988 through 1995.
While the yellow-billed cuckoo is common east of the Continental Divide, biologists estimate that more than 90 percent of the bird's riparian habitat in the West has been lost or degraded. In the U.S., 350 to 495 pairs of the bird exist, with just 10 to 20 pairs existing in the mountain West.
"By preserving a species like this, you also preserve habitat for all the species who thrive in those areas, and also save wetlands for flood control," Swenty said. "The American Public is coming to realize just how much flood control we have lost from filling in wetlands."
The listing proposal cites threats from loss of riparian habitat as a result of conversion to agriculture, dams and river flow management, bank protection, overgrazing, and competition from exotic plants as key factors in their decline.
Critical habitat for the bird will include Colorado, Swenty said, with a published map expected early in 2014.
Adult yellow-billed cuckoos have moderate to heavy bills, somewhat elongated bodies and a narrow yellow ring of colored bare skin around the eye. The plumage is loose and grayish-brown above and white below, with reddish primary flight feathers. The tail feathers are boldly patterned with black and white below. They are a medium-size bird about 12 inches in length, and weigh about 2 ounces. The species has a slender, long-tailed profile, with a fairly stout and slightly down-curved bill, which is blue-black with yellow on the basal half of the lower mandible. The legs are short and bluish-gray.
Western yellow-billed cuckoos prefer isolated wooded riparian corridors surrounded by extensive arid uplands.
The American Bird Conservancy says the proposed threatened listing is not enough to save the bird.
"The draft rule does not address the threats or propose more effective conservation measures such as removing cattle from riparian areas and restricting the use of pesticides in adjacent agricultural areas," said Steve Holmer, senior policy adviser with American Bird Conservancy.
As long-distance, nocturnal migrants, yellow-billed cuckoos are vulnerable to collisions with tall buildings, cell towers, radio antennas, and wind turbines. A recent report at towers found 568 deaths of the bird at 17 towers. Researchers have found that by extinguishing steady-burning red lights on towers, nighttime bird fatality rates can be reduced by more than 70 percent. Birds are not as likely to be attracted to and collide with towers that are lit with only red flashing lights or white flashing lights.
"In addition to working with farmers and ranchers, we urge that a financial incentive program be adopted to change the tower lighting known to reduce deaths," Holmer said.
The public comment period on the proposed listing ended Dec. 2. A critical habitat map and economic impact study is expected to be released in early 2014.
