Southern Sierra Research Station

...conserving biological diversity through research

Current Research

Breeding Biology and Population Dynamics of Yellow-billed Cuckoos

The Yellow-billed Cuckoo (Coccyzus americanus) is a neotropical migrant that historically bred in riparian habitats throughout much of North America. Since the late 1800's many of the forests that cuckoos depended upon, particularly in the West, have been destroyed or degraded by human activity. As a result, both the range and numbers of breeding cuckoos have decreased dramatically and the western subspecies is currently a candidate for Federal Endangered Species status.

Our research focuses on documenting the reproductive biology of this poorly known species and developing survey techniques that reliably estimate numbers of breeding birds in an area. We conduct our research in the Kern Valley in CA and along the Lower Colorado River from Lake Mead south to the US Mexico border. These are arguably the two largest remnant western Yellow-billed Cuckoo populations within their entire range.

Breeding Biology and Population Dynamics of Southwestern Willow Flycatchers

We have monitored a population of endangered Southwestern Willow Flycatchers (Empidonax traillii extimus) on the South Fork Kern River since 1989. We have been particularly interested in understanding the consequences of Brown-headed Cowbird (Molothrus ater) parasitism for flycatcher reproductive success and population dynamics. Despite control efforts that have effectively reduced parasitism rates and increased reproductive success, the Southwestern Willow Flycatcher population in the Kern River Valley has yet to increase in size. We are currently investigating the roles that habitat quality, food abundance, and geographic isolation play in limiting population growth.

Distribution and Ecology of Wintering Willow Flycatchers

We are increasingly interested in the distribution and ecology of wintering Willow Flycatchers. We have traveled to Central America (Costa Rica, Panama, El Salvador, Guatemala, and Mexico) and parts of South America (Ecuador) to determine whether Willow Flycatchers are present in areas where, historically, they were known to winter. On these trips, we capture birds and mark them with bands to estimate survival and winter site fidelity between years. In collaboration with other researchers, we collect small samples of DNA to determine the sex and subspecies of captured individuals and pluck single feathers for stable isotope analysis that will allow us to link wintering and breeding populations of flycatchers.

Southern Sierra Flammulated Owl Presence/Absence Surveys

Flammulated Owls are small, nocturnal, neotropical migrants that vocalize quietly and are rarely seen. They primarily inhabit mid-elevation montane forests, in particular ponderosa pine (Pinus ponderosa), Jeffrey pine (Pinus jeffreyi) mixed conifer and fir (Abies sp.) habitats. Historically, these diminutive owls have been missed in most nocturnal owl surveys because they do not arrive on their breeding grounds until late April to mid-May. Thus, relatively little is known about their distribution or abundance. To obtain more information about their distribution and abundance, in 2011 we began a monitoring program conducted Flammulated Owl surveys in Sequoia National Forest. These surveys were part of a coordinated effort by the Partners in Flight Western Working Group (PIFWWG) to conduct Flammulated Owl surveys throughout their western range. The data gathered from this research will be used to aid in the development of a long-term Flammulated Owl monitoring strategy and to contribute to more detailed studies of Flammulated Owl demography.

Management Efforts

Removal of non-native Vegetation

Each year we survey the South Fork Kern River for non-native plant species such as Purple Loosestrife, Salt Cedar, and Russian Olive. These invasive species can dramatically alter the hydrology of wetlands and riparian areas and destroy specialized ecological interactions among native species if left unchecked.