DDT Threatens Cuckoos

WASHINGTON (CN) - With only 1,000 breeding pairs remaining, the yellow-billed cuckoo in the western U.S., Canada and Mexico has been proposed for Endangered Species Act protection as a threatened species, according to a U.S. Fish and Wildlife's recent action.

The listing proposal is due to a 2011 settlement between the USFWS and the Center for Biological Diversity (CBD) that resulted in a court-approved five-year work plan to fast-track listing decisions for hundreds of species across the country.

The western distinct population segment (DPS) of the yellow-billed cuckoo is threatened by habitat destruction from dams, agriculture, utility towers and wires, and non-native species. Climate change is expected to worsen these threats.

"The yellow-billed cuckoo, often called the 'rain crow' for its habit of singing right before storms, breeds in streamside gallery forests of cottonwood and willow that once thrived along nearly every water body in the West," the CBD noted in its press release.

The cuckoo winters in South America and breeds in North America. It is about a foot long and weighs a mere 2 ounces. Because it travels and feeds outside the United States, it is susceptible to the pesticide DDT, which is banned in the U.S. but still used in other countries. "Yellow-billed cuckoos are exposed to the effects of pesticides on their wintering grounds, as evidenced by DDT found in their eggs and eggshell thinning in the United States," according to the action.

Much of the species' habitat is near agricultural sites, so there is a potential for direct and indirect effects to a large segment of the cuckoo's population from the use of DDT through the birds' health and availability of prey. These changes can affect reproductive success, and ultimately, shrink their occupied range, the action noted.

The cuckoo lives in riparian, or streamside, habitat and is therefore affected by the construction of dams and other artificial alterations of waterways such as channelization. The changes to the natural waterways in an area also contribute to increases in wildfires, loss of native vegetation and the increase of invasive non-native species. Vast tracts of natural riparian habitat are chopped up by these changes and others, including developments, agriculture and infrastructure such as utility towers.

Breeding pairs of cuckoos require large "patches" of unfragmented riparian habitat and are currently found only in the least-fragmented areas. "This observed preferential use of large patches strongly suggests that the DPS is sensitive to fragmentation and reductions in habitat patch size. Moreover, patch-size reduction combined with the scarcity of larger patches keeps the yellow-billed cuckoo breeding population size depressed. Such effects prevent the western yellow-billed cuckoo from reversing its long-term decline in population and range," the agency said.

The agency estimates that the number of total breeding pairs is between 680 and 1,025, and acknowledges that the breeding population may actually be lower than these estimates, and that the population is continuing to decline. However, since the geographic extent of the cuckoo's range remains widespread, and because various conservation projects are in the planning stage to help the birds, the agency determined that this DPS of the cuckoo best meets the definition of a threatened species, rather than an endangered one.

"The petition to protect yellow-billed cuckoos was the first I ever worked on, back in 1998. I had no idea then that getting protection for this severely imperiled songbird would take 15 years, but I'm glad it finally has a great chance of recovering," Noah Greewald, the CBD's endangered species director was quoted as saying in the group's press release.

Comments and information are due Dec. 2.

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