Yellow-billed Cuckoo (Coccyzus americanus): A Technical Conservation Assessment

In western North America, yellow-billed cuckoos (Coccyzus americanus) have undergone catastrophic declines; the eastern subspecies has undergone less rapid declines in most areas since approximately 1980. Direct loss and degradation of low-elevation riparian woodland habitats have been cited as the primary causes for the declines in yellow-billed cuckoos in the western portion of the range. Factors contributing to habitat loss and degradation include alteration of flow schemes in rivers and streams; diversion of water for agricultural and municipal purposes; urban expansion; livestock grazing, which affects understory vegetation and cottonwood/willow recruitment; and pesticide applications which decrease local food supplies and potentially induce toxic accumulations in cuckoos. In the east, the reasons for the now widespread declines are less clear. One potential factor contributing to declines across this species’ range in North America is the loss of forested habitat on its wintering grounds in South America. However, little is known of its ecology or distribution in South America, and this remains an area in need of further research.

David A. Wiggins, USDA Forest Service, Rocky Mountain Region