The Yellow-billed Cuckoo (Coccyzus americanus) is a rare bird in the western United States, with an estimated population of 475 to 675 pairs by the late 1980s (Laymon and Halterman 1987). Its historic range has contracted dramatically, particularly in the Pacific Northwest, where it disappeared as a breeding bird from British Columbia, Washington, and Oregon between the 1920s and 1950s (Roberson 1980; Gaines and Laymon 1984; Marshall et al. 1996). It is under review for listing as a threatened or endangered species by the U.S. Fish and Wildlife Service, and it is listed as endangered, threatened, or a species of concern by state wildlife agencies in California, Oregon, and Arizona (Hughes 1999).