Cooperative Fish and Wildlife Research Units Program: Arizona
Education, Research and Technical Assistance for Managing Our Natural Resources

Goal: 1) assess evidence of reduced genetic diversity or increased inbreeding levels in western yellow-billed cuckoos within isolated breeding sites, 2) measure genetic structuring between eastern and western cuckoos. Due to the extensive loss and fragmentation of western riparian forest, yellow-billed cuckoos (Coccyzus americanus, ‘cuckoos’) have suffered range-wide declines and in the western United States are now restricted to small, isolated breeding sites. Conflicting evidence exists both for local interbreeding within isolated sites, and for strong dispersal capabilities in this long-distance Neotropical migrant. It is unclear if the current small acreage and isolation of western riparian forest is unfavorable to dispersal and population growth, further reducing genetic diversity in this threatened population. Analysis of microsatellites (simple DNA sequence repeats) from individuals representing geographically distinct breeding sites of varying size and level of isolation may inform the recovery of this threatened population, such as recommending minimum breeding patch sizes and levels of spatial connectivity. This study also provides further insight into the nature of genetic differentiation between eastern and western cuckoos.