By Rex Graham
The Western Yellow-billed Cuckoo, a secretive, avian apparition of streamside woodlands in the western United States is finally getting a moment of fame — and desperately needed habitat protection as its numbers continue to plummet.
The U.S. Fish and Wildlife Service (FWS) on August 14, 2014, formally proposed establishing 546,335 acres of remnant riparian woodlands scattered along streams in nine western states as critical habitat for the western Distinct Population Segment (DPS) of the Yellow-billed Cuckoo. The species is a prized find on dozens of bird festivals and birding tours in Arizona, New Mexico and California.
The proposed rules is coupled to an earlier one listing the western DPS of Yellow-billed Cuckoos as threatened under the Endangered Species Act (ESA).
Stunning and shy
The Yellow-billed Cuckoo is a stunning beauty – a slender, long-tailed bird about 12 inches in length (males are slightly smaller than females) with a yellow lower mandible of its downward-curved bill. The bird is grayish above, white below, and the tail is boldly patterned below in black and white. The cuckoo eats a wide variety of large insects, tree frogs, small liza
rds and other prey found in increasingly rare cottonwood and willow woodlands along streams.
Legal battle to list
The proposal by the FWS comes 16 years after an initial petition by environmental organizations to list the western population as an endangered sub-species. The organizations filed lawsuits to force the FWS to act, however the FWS had more pressing priorities, and the genetic differences between the western and eastern populations of Yellow-billed Cuckoos were ambiguous.
The FWS critical-habitat proposal is to be published Aug. 15 in the Federal Register. Comments will be accepted through October 14, 2014, at http://www.regulations.gov (docket number FWS–R8–ES–2013-0011).
A final determination is expected in 2015. In earlier comments to the FWS, the Center for Biological Diversity said critical habitat designation “is the most straight-forward, effective and appropriate means” to protect the western population of the Yellow-billed Cuckoo from extinction.
The 546,335 acres of riparian habitat is composed of 80 units in Arizona, California, Colorado, Idaho, Nevada, New Mexico, Texas, Utah, and Wyoming. Maps for the 80 units are available online. The Western Yellow-billed Cuckoo (Coccyzus americanus occidentalis) also has historically nested in Montana, Oregon, and Washington, but the bird hasn’t been confirmed breeding there in years.
For most birders in the West, the Yellow-billed Cuckoo (Coccyzus americanus) is seen only in field guides.
Skilled biologists have watched individual adults perch for hours on distant, high limb, and then suddenly dart away and return with a katydid or grasshopper. Such “sit and wait” predators that spend time high in a cottonwood tree are difficult to spot.
Occasionally, those with an educated ear for the low-pitched “kowlp”” calls of the “rain crow” are rewarded. Unmated cuckoos give “cooing” notes day and night. Mated pairs use soft “knocker” notes as a warning near the nest.
Hearing cuckoo calls
The low-pitched calls carry long distances through their preferred habitat of at least 100 acres of unbroken stands of streamside, or riparian, woodland. Researchers have been monitoring those areas for decades, relying primarily on hearing rather than seeing the birds.
Biologists survey riparian woodlands by a set protocol: after arriving at a predetermined spot, they wait a minute, and then broadcast a pre-recorded cuckoo call.
Upon listing, special permits allow them to broadcast the calls in the hopes of eliciting a “call back.”
After playing the first call, biologists remain quiet for another minute, listening for a reply. They repeat the playback-listening sequence for four more cycles before moving on.
There’s a catch with the monitoring technique: mated pairs routinely don’t call back: they prefer to remain silently hidden in the cottonwoods. Very rarely, highly skilled biologists see a cuckoo without hearing it first.
“They’re like a ghost bird,” said Joe Silveira, a wildlife biologist at the Sacramento National Wildlife Refuge Complex, where the cuckoos are declining.
“Every encounter you have with a Yellow-billed Cuckoo is memorable. They have a beautiful gray color and a black tail with white patches. It feels like a fleeting moment when you see one because they are so hard to find.”
By any monitoring measure, Western Yellow-billed Cuckoos are vanishing from riparian habitats in the West. Biologists like Silveira and others with the FWS, U.S. Geological Survey (UCGS) and other federal and state agencies, environmental organizations and universities are deeply concerned about the bird’s rapid decline.
While loss of breeding habitat is a top concern, the loss of wintering habitat and pesticide use in breeding and wintering grounds could also be hurting cuckoos.
In 1998 the Southwest Center for Biological Diversity and a coalition of 23 groups filed a petition with the Interior Department to list the Yellow-billed Cuckoo or the western subspecies under the Endangered Species Act.
The department had higher priorities at the time. It didn’t act until October 3, 2013, by proposing to list the western DPS of the yellow-billed cuckoo as a threatened species in the western United States, Canada, and Mexico. The comment period for that proposal closed on December 2, 2013.
The western and eastern races of Yellow-billed Cuckoos nest in separate, non-overlapping breeding territories.
The breeding season of the western is four to eight weeks later than the eastern. Western cuckoos are larger with proportionately larger bills and grayer above than the eastern cuckoos, which are more brown than gray.
Despite the differences, scientists have disagreed over whether the two populations are separate subspecies.
In 2014, a genetic analysis of a single gene shared by western and eastern cuckoos found “slight, insignificant differentiation between the two subspecies.” The study published in BioONE, recommended sequencing the entire genomes of the two races to determine if separate taxonomic designation as two subspecies was warranted. However, the BioONE findings are controversial.
“They tested areas of the genome that are highly conserved and won’t show a difference,” said Steven Laymon, a wildlife biologist with the FWS office in Sacramento, Calif. “The definitive genetic analysis hasn’t been done yet.”
The Endangered Species Act provides threatened or endangered listing if one population is discrete and separate from another “due to physical, physiological, ecological, or behavioral factors.”
Death of many cuts
What is unequivocal about the western population of Yellow-billed Cuckoos is that more than 90 percent of their native riparian woodland habitat of cottonwood and willow has suffered an ecological near-death from multiple cuts.
The death blows have been in the form of deforestation for agricultural, dams and river flow management, stream bank protection, livestock overgrazing, human recreation, and invasion of the Tamarisk shrub, which crowds out cottonwoods and other native trees, shrubs and other plants.
Only a tiny fraction of the U.S. land mass is still classified as riparian habitat. Unfortunately, the threatened cuckoos and dozens of other species of migratory birds, including many listed as threatened or endangered, require the vanishing habitat.
Wildlife and water
Ecologists warn that climate stress, increased water withdrawals from rivers, and more human uses for the land may push riparian ecosystems – and the species that require them – toward collapse.
Approximately 350,000 acres of riparian habitat proposed for federal protection for cuckoos is owned by private landowners. The remaining 200,000 acres are federal or state property.
More than 193,000 acres are excluded in the FWS proposal from critical habitat designation because conservation actions in those areas already manage for and protect the Western Yellow-billed Cuckoo and its habitat.
“Most of the 550,000 acres of designated critical habitat are in flood plains, which couldn’t be developed even if cuckoos were not there,” Laymon said. “Only 2,000 to 3,000 acres have possible development potential, so we don’t expect a lot of opposition to the plan.”
Biologists have used scant funding available to study the Western Yellow-billed Cuckoo for decades. There are only an estimated 345 breeding pairs of Western Yellow-billed Cuckoos in the entire American Southwest, mostly in Arizona, New Mexico and California. There are an additional 430 pairs in northwest Mexico, according to the FWS.
The model of optimal cuckoo habitat will serve as a template for how critical habitat areas will be maintained and improved. However, if you build it, cuckoos won’t necessarily come.
Good habitat, no cuckoos
The San Joaquin River northeast of San Francisco, Calif., and the Columbia River in Oregon and Washington have what appears to be ideal cuckoo habitat, but cuckoos don’t use it.
There are a few bright spots. The birds are found in stable numbers along the San Pedro River east of Tucson, Ariz. The San Pedro is one of the only undammed rivers in the West, and as a result has prime riparian habitat.
The Rio Grande south of Albuquerque and immediately north of the Elephant Butte Reservoir is another stronghold. In 2012, the U.S. Interior Department’s Bureau of Reclamation detected 121 Western Yellow-billed Cuckoo breeding territories in the Middle Rio Grande Basin, an increase of 27 percent over a 2009 survey conducted in the same area.
‘No take’ land
The Center for Biological Diversity, in an earlier comment to the FWS, said, “Habitat destruction in the case of the Western Yellow-billed Cuckoo is a greater threat than direct take” of the birds themselves.
Under the “illegal take” provisions of the new FWS proposed rule, streams running through 546,335 acres of habitat would be protected from channelization, impoundment, bank stabilization, water extractions, diversions, channel clearing and other actions that alter the hydrology of the habitat.
Extreme breeding behavior
Large home ranges provide optimal opportunity for cuckoos to avoid the hawks and find their preferred prey: sphinx moth larvae, cicadas, tree frogs, lizards, gypsy moths, toxic hairy and spiny caterpillars, katydids and other large insects and small vertebrates.
The Western Yellow-billed Cuckoo breeds in surprising ways that are both finely tuned to its environment and among the most extreme of all birds.
Rather than migrating north in early spring with other Neotropical migrants, cuckoos reach their breeding territories in the West in June. By that time, large insects have fattened up.
Rainfall is crucial to the large-insect prey cuckoos prefer, but in the Southwest, spring and summer rains are hit-or-miss. In satellite images, the West is a patchwork of brown and green. Cuckoos gravitate to the greener areas.
A difficult species
“It’s a difficult species to understand because it works on a different geographical scale than ornithologists are used to conceptualizing,” said Charles van Riper III, an ecologist with the USGS Sonoran Desert Research Station in Tucson, Ariz. “We tracked one cuckoo that was nesting along the Rio Grande in Albuquerque fly to Denver for the afternoon and then flew back.
“It’s a different bird than most people are used to working with,” van Riper said.
Cuckoos build rudimentary nests, placing the bare platforms of twigs on horizontal branches. There’s no soft lining. In years when cicadas or caterpillars are bountiful, cuckoos lay as many as five eggs.
All eggs hatch after an 11-day incubation and chicks leave the nest at 5 to 6 days later. “The species has the shortest period between egg laying and fledging of any known species of passerine [perching] bird,” said Laymon. “When the fledglings leave the nest they can’t fly – they hide in the foliage.”
Laymon and van Riper said parents and sometimes one or two adult “helpers” feed the chicks about 10 times a day. The low number of intraday feedings is thought to minimize attention from hawks and other predators.
For hungry chicks, one big caterpillar is a nutritious, calorie-rich meal. A fly fisher in Arizona hooked a Yellow-billed Cuckoo with a cicada lure he had cast over a stream, Laymon said.
By mid-September, most Western Yellow-billed Cuckoos have headed back south to Central and South America, but even their migration routes are mostly mystery.
When Bureau of Reclamation biologists attached lightweight geo-locator tracking devices to one cuckoo that had nested in New Mexico along the Middle Rio Grande, it flew south in September to Mexico City, and then flew to Costa Rica, Panama and Peru. It spent most of the winter in the Amazon area, including Paraguay and northern Argentina, and then zig-zagged north to Venezuela, Cuba, Mexico’s Yucatan Peninsula, northwest through the Sonoran Desert and ended up at the same cottonwood tree in Albuquerque.
Van Riper is quick to point out that tracking one bird isn’t nearly enough information to understand a species that continually adapts to environmental conditions.
Other biologists who monitored the cuckoo’s numbers and nests in 2011 and 2012 never actually saw the birds. In the field, they would hear the ubiquitous chirps of hummingbirds and scrapes of cottonwood leaves in the breeze, but very rarely the kowlp call of a cuckoo.
“They are very difficult to study,” said Matthew Johnson, an ecologist and director of Northern Arizona University’s Colorado Plateau Research Station in Flagstaff, Ariz. “I’ve been studying this species for 20 years and places like the San Pedro River east of Tucson you will see fairly constant numbers of cuckoos, but other places you see them one year, but not another.”