Yellow-billed Cuckoo Breeding Phenology and General Nest Site Characteristics in Western Colorado
Adam Petry1*
1Western Biology, LLC, P.O. Box 482, Hotchkiss, Colorado, U.S.
Inventory and monitoring efforts for the elusive Yellow-billed Cuckoo (Coccyzus americanus, YBCU) have been historically limited and inconsistent in western Colorado and many questions persist about the species’ population status, breeding phenology, and habitat use in the region despite a significant recent increase in habitat management and vegetation removal projects. Although YBCU are rare and exhibit low solicited and unsolicited vocalization rates, existing data show a direct correlation between increased YBCU survey efforts and increased YBCU detections. In 2022, we conducted the first comprehensive spatially-balanced inventory for the species in western Colorado, which identified two surprising breeding hotspots located in fallow agricultural habitat dominated by Russian Olive (Elaeagnus angustifolia) and disconnected from traditional riparian corridors long-associated with species presence. In 2023, we discovered the latest known YBCU nest (August 5-24 in a Russian Olive fencerow) and site occupancy (September 20) in state history and subsequently performed a historical records review of probable and confirmed YBCU breeding attempts in western Colorado. Preliminary data indicate that YBCU incubation in western Colorado may peak between August 1-15 and fledging between August 15-30 and that both nest phases may occur later than previously anticipated. Preliminary data also demonstrate that YBCU continue to select for and potentially prefer Russian Olive for nesting in both riparian as well as agricultural and xeroriparian land use types. We propose Russian Olive may provide increasingly important surrogate, successional, and edge habitat for a variety of avifauna, especially as the health of riparian cottonwood galleries continues to decline across much of the Colorado Plateau. We recommend additional surveys and research to improve understanding of YBCU ecology and inform habitat management guidelines. We also recommend habitat management projects account for the intrinsic wildlife value of Russian Olive by protecting mature shrubs and monotypic stands as refuges for imperiled birds, at least until habitat restoration and replacement sites can ensure adequate long-term care and maintenance, water security, and viability of native plantings.