I am working under the premise that successional riparian habitat is the key that is missing for the continued successful reproduction of riparian obligate species and specifically the Western Yellow-billed Cuckoo. As I read through papers, I am wondering if this has been quantified before?
Isabella Reservoir has been drawn down for several years prior to the drought and now 9,000 acres of lake bottom have been laid bare. The primary stage of new riparian forest in the reservoir inundation zone is developing well and may provide excellent habitat for the cuckoo as it is replicating the meanders of the old river quite nicely.
Does anyone have any information to confirm my suspicions or correlative data?
Conference Paper Riparian habitat dynamics of the western yellow-billed cucko...
I do not have data that confirm your suspicions, however your premise: 'successional riparian habitat is the key that is missing for the continued successful reproduction of riparian obligate species and specifically the Western Yellow-billed Cuckoo' may be weak, and the subsequent one: 'the primary stage of new riparian forest in the reservoir inundation zone is developing well and may provide excellent habitat for the cuckoo as it is replicating the meanders of the old river quite nicely' even weaker.
An obligate organism complete whole or parts of its life cycle in a suitable host or habitat. So I would assume that you have some evidence which suggest that obligate species completed whole or parts of their life cycles in hitherto undegraded tertiary riparian habitat without opportunity and alternative habitats in which same can be completed. This evidence would clearly define the extent of changes from tertiary state in primary state (again some prior evidence of which ought to be available) which may or may not adequately support significant populations of obligate species to consolidate main and secondary premise.
complete its life cycle
I have found data backing up my hypothesis. Surveys conducted in 2009 showed that 84% of the cuckoo detections were in the location where the river braids in the wildlife area (Henneman 2010). Only 16% of the 69 cuckoos detected during the field season were found upstream of the South Fork Bridge on Sierra Way, where the forest has become decadent along the single river channel corralled by three bridges. Due to legal restrictions that maintained the Isabella reservoir peak at 350,00 acre feet or below for 10 years, the mid-successional forest recorded an almost 80% increase in the number of cuckoos from 14 individuals in the 1985-87 season to 69 individuals in 2009 (Laymon and Halterman 1989), (Henneman 2010).
Thank you for your observation. I am not inferring that the primary successional stage is where the nesting strata would be found but that without succession the habitat degradation at climax stage is no longer conducive to successful rearing of young. As the forest ages from primary to mid-age succession is where I surmise the best nesting strata would be found (cottonwood-willow mid-succession ~8-20 years of growth.) It is my hypothesis that alteration of natural meandering streamcourses to controlled waterways is where the problem begins for riparian systems that are limited by trees with a short life span.
Based on our work under the Lower Colorado River Multi-Species Conservation Program (www.lcrmscp.gov) since 2008, the answer to your question is yes. We have been intensively nest-searching (for cuckoo nests) in all cottonwood-willow (CW) plantings at least 2 years old, including radio-tracking over 100 adults, and have found a preference for nesting in 2-4-year-old CW plantings, including higher nesting densities. It could be argued that we don't find all nests and may miss more nests in older trees; their nests can be hard to find due to the secretive nature of cuckoos. But the use of telemetry reduces bias and makes our results more compelling. Additionally, we have significantly more survey detections in the young phases. We suspect this may be related to more insects being in young CW trees, young Salicaceae leaves having more water, and young trees having more young leaves and continuing to produce new leaves through July - the peak nesting period - unlike older trees that stop producing new leaves by late June. All our reports from 2008-2015 can be found on the website, http://www.lcrmscp.gov/steer_committee/technical_reports_species.html, under yellow-billed cuckoo, D7. These contain references to the above, but I can provide them for you if you don't want to wade through hundreds of pages of technical reports!