The Yellow-billed Cuckoo in Northwestern California

Prior to 2000, the Yellow-billed Cuckoo (Coccyzus americanus) had been recorded in northwestern California (defined here as Humboldt, Del Norte, Trinity, northern Mendocino, and western Siskiyou counties) on six occasions, all in Humboldt County. To better understand the species’ status within this region, we surveyed for it during the breeding season in 20 of the 24 years from 2000 to 2023, primarily along the lower Eel River in Humboldt County and in suitable habitat elsewhere in Humboldt and Del Norte counties. We found the species to occur more frequently than previously known, detecting 1–3 individuals in 9 of the survey’s 20 years. Also, we evaluated the 23 incidental Yellow-billed Cuckoo observations during the same period; these include the first known records for Del Norte County. Most detections were within riparian scrub or riparian forest dominated by willows (Salix spp.) and Red Alders (Alnus rubra), often with scattered Black Cottonwoods (Populus trichocarpa). Although no nests have been confirmed to date, observations imply occasional breeding in Humboldt County.