The museum is currently working on six southern California field projects. The study areas are all in Ventura County, on the Santa Clara River (SC River), The Channel Islands National Park, and in the Santa Monica Mountains National Recreation Area. The SC River is a focal point of the WFVZ’s current research

The SC River watershed drains a biologically rich region at the junction of 5 of California’s 10 identified Bioregions, and contains a particularly strong representation of the biodiversity in the South and Central Coast Bioregions. It is one of the few major river systems in the State which still retains much of its natural hydrology. The river provides the ecosystem functions necessary to support many federally listed species and many California State Species of Special Concern, including three endangered bird species, the Least Bells’ Vireo, Southwestern Willow Flycatcher, and Yellow-billed Cuckoo. The river basin also sustains some of the most valuable agricultural resources in the world. It provides water resources for surrounding urban populations, and provides diverse outdoor recreational opportunities.

scriver1  scriver3

The first WFVZ project is on Least Bells’ Vireo (LBVI) nesting on the SC River. This project is in partnership with the U.S. Fish and Wildlife Service, California State University Channel Islands, the U.S. Geological Survey (USGS), and The Nature Conservancy (TNC). Here, the WFVZ is trying to understand the dynamics of LBVI breeding on the river. 

According to the USFWS, the LBVI is an obligate riparian species during the breeding season and is characterized as preferring early successional habitat. Historically, the LBVI was widespread and abundant, ranging from northern California down to Baja California, Mexico. Numbers of pairs of the subspecies have increased on the SC River in the past 20 years, but questions about the impacts of Brown-headed Cowbird parasitism and natural predation still exist for our region. So, the WFVZ has been monitoring nesting pairs on the SCR since 2015.

The data from this project are being used in the development of a model that will be used by the USFWS to predict population sizes and sensitivities to different factors over the next 50 years. The second project on the SC River is a 2-year experiment evaluating alternative methods for controlling cowbird parasitism of LBVI nests. The WFVZ is in partnership with TNC on this project. Extensive breeding habitat loss and brood parasitism by the cowbird contributed to the initial range-wide declines of the subspecies. However, current levels of parasitism of LBVI nests are not high on the SC River, so strategies for addressing parasitism in the future are being tested.

The third WFVZ project on the river is the Bird Counting Project. Since 2010 the WFVZ has partnered with the Friends of the SC River on the Hedrick Ranch Nature Area (HRNA) to monitor birds by point counts, and in 2011, Dr. Hall began counting birds on all TNC properties on the river. As of 2017, this research is now being conducted on 18 of TNC’s proper- all TNC properties on the river. Data on trends in bird numbers are extremely important for managing habitat and other resources for birds, and this project has provided population trend information for more than and other resources for birds, and this project has provided population trend information for more than 100 bird species since it started. 100 bird species since it started.

LBVI banding
Banding a Least Bell's Vireo (Vireo bellii pusillus) at HRNA

The fourth project, which started in September 2017, is in partnership with the California Department Fish and Wildlife (CDFW), USFWS, Stillwater Sciences, Restoration Science, U.C. Santa Barbara and the USGS. In this project, the WFVZ will survey for two years for the Southwestern Willow Flycatcher (SWFL) and Yellow-billed Cuckoo (YBCU) on the SC River, and then model the habitat suitability of the river for future possible expansion of the species.

According to the USFWS, SWFL was federally listed as Endangered in 1995.  SWFL breed in dense riparian habitats where surface water is present or soil moisture is high enough to maintain the appropriate vegetation characteristics. The YBCU was listed as Endangered in 2014. Halterman and others have summarized that even by the 1940s it was observed that YBCU were declining in California, due to habitat loss and alteration. In California, habitat often consists of willows mixed with cottonwoods.  The present project will further identify the characteristics of the riparian vegetation used by cuckoos and Southwestern Willow Flycatchers in southern California, as well as more thoroughly determine how many of these birds are actually breeding on the SC River.

Read more about Santa Clara River conservation here 

Yellow-billed Cuckoo
Yellow-billed Cuckoo (Coccyzus americanus) spotted on
 SC River.
©Adam Searcy