Southern Sierra Research Station

...conserving biological diversity through research

Lower Colorado River Yellow-billed Cuckoo Research

The Lower Colorado River (LCR) Multi-Species Conservation Program (MSCP) is a coordinated, comprehensive, long-term, multi-agency effort, with goals including habitat conservation, recovering threatened and endangered species, and preventing the listing of additional species (LCR MSCP 2004). The MSCP encompasses the historical floodplain of the Colorado River from Lake Mead to the United States-Mexico Southerly International Boundary, a distance of about 400 river miles. The program aims to create more than 3,278 ha (8,100 acres) of riparian, marsh, and backwater habitat for six listed species and 21 other species native to the lower Colorado River, including at least 1,639 ha (4,050 acres) of habitat for the riparian obligate Yellow-billed Cuckoo (LCR MSCP 2004).

Yellow-billed Cuckoos are one of twenty-six Focal Species included in the MSCP. Our project objectives are to 1) conduct comprehensive, repeatable Yellow-billed Cuckoo surveys in all potentially suitable habitat types within the MSCP boundary, 2) determine breeding habitat selection and preferences in the study area, and 3) evaluate the effectiveness of the current breeding season survey methodology, refining it to use over the term of the MSCP.

The goals behind these objectives are to identify the key elements required for successful cuckoo reproduction and successful Yellow-billed Cuckoo habitat restoration projects. From the identification of successful restoration areas we will recommend sites for future restoration efforts based on their probability of successfully attracting cuckoos, and provide guidelines to evaluate the success of future habitat restoration projects. Overall, the information obtained from this research will improve our capacity to manage this species.

    Some preliminary results:
  • The analysis of annual survey data has enabled us to identify the cuckoo's response to maturing restoration habita. For example, in 2001, we recorded greater occupancy of restored habitat compared to natural habitat(63% vs. 49%), stressing the importance of habitat restoration for cuckoo recovery in this region.
  • Yellow-billed Cuckoos select nest sites at cooler and more humid locations which may improve nest success. Although microclimate cannot be manipulated directly, providing a site with suitable nesting microclimates can be achieved indirectly through changes in vegetation characteristics and possibly soil moisture. Ensuring that restoration sites have areas of dense canopy and high humidity may ensure the availability of suitable nesting locations for Yellow-billed Cuckoos.
  • Cuckoo breeding and cicada abundance are correlated in natural systems, but does not hold true at restoration sites. Less is known about prey base at the restoration sites.
  • Creating multi-structured habitats by establishing native small trees spaced randomly apart and encouraging large native tree growth will increase preferred nesting and foraging areas for cuckoos as well as possibly increase cicada abundances.
  • Through intensive nest searching we have discovered large increases in breeding territories at MSCP restoration sites, and this year we witnessed nest parasitism by cuckoos for the first time in the study area. We also noted an apparently hight nest failure rate at restoration sites compared to Bill Williams River nests. Over the past four years of color-banding and resighting banded LCR cuckoos, we have begun to gather valuable data on dispersal, including evidence of strong natal and breeding site fidelity.
  • Radio telemetry of cuckoos over the past three seasons has revealed important behavioral information that would not be possible through other means of study. For example, from 2009 - 2011, we have consistently obtained mean home range estimates close to 20 ha, for both breeding and transient cuckoos, which we can now use as a basis for habitat occupancy analyses at an appropriate spatial scale of sample unit.

References

Lower Colorado River Multi-Species Conservation Program. 2004. Lower Colorado River Multi-Species Conservation Program, Volume III: Biological Assessment. Final December 17. (J&S 00450.00.) Sacramento, CA.

More information about our LCR MSCP research can be found at the MSCP Technical Reports web page (under the Yellow-billed Cuckoo section; D-7: Yellow-billed Cuckoo Presence/Absence Surveys).