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

Wohner, PJ, SA Laymon, JE Stanek, SL King, RJ Cooper. 2021. Challenging our understanding of western Yellow-billed Cuckoo habitat needs and accepted management practices. Restoration Ecology 29(3): e13331.


Riparian restoration in the southwestern United States frequently involves planting cottonwood (Populus spp.) and willow (Salix spp.) cuttings or seedlings. In the absence of flooding and gap-forming disturbance, planted forests often senesce without further young tree recruitment. This has largely been the case in riparian systems in California that historically supported state endangered western Yellow-billed Cuckoo (Coccyzus americanus; Cuckoo). Associated with riparian forest maturation has been around an 85% decline in Cuckoo population numbers in approximately the past thirty years. Other riparian species of concern show a concomitant decline, indicating the problem is not specific to Cuckoo. Although varying hypotheses exist for the recent decline, alternative management practices have not been sufficiently explored to rule out breeding ground habitat quality as a major contributing factor. Few intensive Cuckoo datasets currently exist to test hypotheses about breeding habitat quality due to extremely low populations in the remaining occupied sites. We used a historical (1986–1996) spot mapping dataset from the South Fork Kern River Valley, California to identify vegetation characteristics related to Cuckoo and five other sensitive riparian bird territory densities. We found Cuckoo densities were positively associated with increased vertical vegetative structure 1–5 m above ground with a threshold for mean tree height. Sensitive species densities were also related to vertical structure and started to decline with stand height greater than 6–8 m. Low and mid canopy vertical structure started declining after about age eight. Naturally regenerated sites had higher densities of most sensitive bird species than planted sites. We provide ideas for restoring mature forest with little low to mid canopy vertical structure.