YOLO COUNTY BIRD SPECIES WATCHLIST (PDF of species listed, and their status, available here)
Yellow-billed Magpie (Pica nuttalli)
Endemic resident of California in the Sacramento and San Joaquin valleys (from Shasta County south to Kern County), and in valleys of the coast ranges from San Francisco Bay south to Santa Barbara County; year-round resident of Yolo County. Forages primarily in open oak woodland interspersed with grasslands or cultivated lands, open riparian woodland, and savanna. Gregarious nester. Although not listed under state or federal ESA, there is conservation concern for this species owing to its high susceptibility to West Nile Virus, and the species has been identified by the National Audubon Society as a "yellow list" species owing to its endemic status and relatively small population size, and because of the threat of habitat loss from development in its preferred habitats. Population monitoring efforts are underway. No other current conservation measures are recommended at the present time.
Oak Titmouse (Baeolophus inornatus)
A resident, endemic species intimately linked to acorns and oak-containing habitats, this species has declined in abundance, apparently because of reductions in suitable habitat area. A cavity-nesting species that does not excavate, these birds are associated with oak woodlands having relatively dense canopy cover, and tree removals for firewood or range improvement may render habitat unsuitable. Conservation concerns for this species may be addressed by maintaining or restoring moderately high canopy densities in oak woodlands; maintaining trees, snags, or dead limbs on woodlands, especially those with excavated or natural cavities; by protecting the oak woodland landscapes from disturbance and fragmentation in order to assure adequate recruitment of new oaks; and by managing oak woodland habitats to sustain populations of cavity excavators (woodpeckers).
Burrowing Owl (Athene cunicularia hypugaea)
The Burrowing Owl is a California Species of Special Concern and an Audubon Society Blue List species, indicating it is undergoing non-cyclic population declines and extreme habitat loss. The breeding range of the western subspecies extends south from southern Canada into the western half of the United States and down into Baja California, Mexico, and central Mexico, and it is a year-round resident of Yolo County. Habitats include dry open rolling hills, grasslands, fallow fields, sparsely vegetated desert scrub with gullies, washes, arroyos, and human-disturbed lands (golf courses, road embankments, airports, cemeteries, etc.) where there is sufficient friable soil for a nesting burrow. The Burrowing Owl is threatened by habitat loss and degradation from rapid urbanization of farmland , particularly in the Central and Imperial valleys. Control and extermination of burrowing mammals pose a risk to the species, as do certain farming practices, such as discing and road and ditch maintenance. The maintenance of large tracts of open grassland and implementation of best management practices are necessary to ensure the long-term viability of the species.
Horned Lark (Eremophila alpestris)
An endemic and non-migratory subspecies (Ruddy Horned Lark, E.a. rubea) found only in the Sacramento Valley, is a rare but regular breeder in Yolo County. They are joined in winter by other subspecies from the north. These birds prefer open country with sparse vegetation, including pasture and fallow fields. Nesting occurs at both the Davis Wetlands and the Yolo Bypass Wildlife Area, as well as other locations on the Valley floor and in the Dunnigan Hills. They seem to avoid locations near orchards, vineyards, trees, power lines, and even fences for nesting. They are threatened by conversion of open land into vineyards and other development, but have benefited from restoration projects, especially those involving large tracts of open country.
Yellow-billed Cuckoo (Coccyzus americanu)
A state listed endangered species, found primarily in riparian habitat. These birds require large unbroken tracts of riparian cottonwoods and willows for nesting, typically a minimum of a mile long and over a hundred meters wide. They are thought to avoid riparian areas with oaks. Due to the loss of this habitat throughout the state, there are now fewer than 100 pairs remaining statewide. They have been extirpated as breeders in Yolo County (and much of the Central Valley) for decades. They occur locally only as passage migrants, but are rarely observed. Restoration projects and riparian forest recovery along the Sacramento River and Cache Creek (including the Cache Creek Settling Basin) on the valley floor offer some hope of restoring this species.
Bell’s Vireo (Vireo bellii)
A state and federally listed endangered subspecies (Least Bell’s Vireo, V.b. pusillus), it is found primarily in riparian habitat. These birds are dependent on riparian cottonwoods and willows for nesting. Due to habitat loss and cowbird parasitism, their population fell to approximately 300 pairs statewide in the 1980s, largely confined to southern California. Since then, they have expanded somewhat. A nesting pair at a restoration project site at the San Joaquin River National Wildlife Refuge in 2005 was the first Central Valley nest record in over 60 years. They have been extirpated from Yolo County for decades and there are no documented records since 1925. However, riparian restoration projects, particularly involving large contiguous tracts of willows along the Sacramento River and Cache Creek (including the Cache Creek Settling Basin) on the valley floor, offer some hope of restoring this species.
Yellow Warbler (Dendroica petechia)
A riparian-dependent species that likely bred historically in Yolo County along rivers and streams. They are currently extirpated as breeders, largely due to habitat loss. Isolated observations of singing males in June suggest recovery is possible, given habitat improvements. They continue to nest in small numbers in the northern Sacramento Valley, and they occur in Yolo County as common spring and fall passage migrants. Restoration projects and riparian forest recovery along the Sacramento River and Cache Creek (including the Cache Creek Settling Basin) on the valley floor offer hope of restoring this species.
Little Willow Flycatcher (Empidonax traillii brewsteri)
It is listed as a Threatened species under the California Endangered Species Act. It is also a Yellow List Species on Audubon’s WatchList 2007, indicating that the species is rare or declining over all or a significant portions of its range. The Little Willow Flycatcher is one of five recognized subspecies of Willow Flycatcher, three of which occur in California. The Little Willow Flycatcher is a rare to locally uncommon summer resident in California from Tulare County north along the western side of the Sierra Nevada and Cascade Range at elevations between 2,000 and 8,000 feet. The species generally nests in riparian sites that are moist, shrubby riparian areas with standing or running water and dominated by willows, cottonwoods, and alders. There is one presumed breeding record at the Wood Duck Ponds in 2003. The greatest threat to Little Willow Flycatcher populations is habitat destruction, degradation, and fragmentation. Projects that reduce or eliminate stream flows may affect the species because it is not known if the species will attempt nesting in the absence of flowing water. Brood parasitism by the Brown-headed Cowbird negatively affects nesting success. Maintenance and restoration of riparian shrub habitats, control of livestock grazing, management of recreational activities affecting local hydrologic conditions, and Brown-headed Cowbird control may be necessary to ensure the long-term viability of the species.
Willow Flycatcher (Empidonax traillii)
A riparian-dependent species that likely bred historically in Yolo County along rivers and streams. In this area, the local subspecies (E.t. brewsteri) has suffered declines similar to that of the Southwestern Willow Flycatcher (E.t. extimus), a state and federally listed endangered subspecies. These birds are dependent on riparian cottonwoods and willows for nesting and likely bred historically in Yolo County. They are currently extirpated as breeders, largely due to habitat loss. Birds that breed farther north (from northern California thru southern British Columbia) occur in Yolo County as rare spring and common fall passage migrants. Restoration projects and riparian forest recovery along the Sacramento River and Cache Creek (including the Cache Creek Settling Basin) on the valley floor offer some hope of restoring this species.
Downy Woodpecker (Picoides pubescens)
A species of low-elevation riparian woodlands (formerly known as the Willow Woodpecker), these resident birds are widespread but not numerous in riparian habitat, where they forage on trees and shrubs by shallow excavation and surface gleaning. Excavates cavities for nests that are subsequently used by other species. Conservation concerns are related to reductions in riparian habitat area and the loss of soft-wooded riparian trees and snags. These concerns can be addressed by increasing riparian corridors or buffers along streams, particularly when the riparian corridors can be linked throughout the region; and through restoring or enhancing the numbers of larger willows, cottonwoods, and other soft-wooded species in riparian habitat.
Western Bluebird (Sialia mexicana)
This species is a non-excavating cavity-nesting species that occurs in a number of woodland and forested habitat types, although it favors oak woodlands and savannas (though not cultivated fields). These birds are severely affected by nest-site competition from introduced European Starlings, which thrive in agricultural landscapes, and bluebird numbers have declined significantly. A preferred food for this species is mistletoe berries; the elimination of mistletoe or the larger and older oaks that contain that parasitic plant can eliminate this species from a region, and this is a significant conservation concern for the species.
Acorn Woodpecker (Melanerpes formicivorus)
A California endemic subspecies intimately linked to oak-containing habitats. These birds live in groups of related individuals, and the birds in each group store acorns in a few granary trees. Conservation concerns for this species can be addressed by maintaining large tracts of land that include a high abundance of oaks and a natural diversity of oak species, maintenance of all trees used as granaries and the inclusion of soft-wooded trees that will serve as replacement granaries, and protection of the oak woodland landscapes in order to assure adequate recruitment of new oaks.
White-breasted Nuthatch (Sitta carolinensis)
This species is permanently resident in oak woodlands and oak-containing riparian corridors, where it forages by gleaning from trunk and limb surfaces, as well as through acorn consumption. As a cavity-nesting species that does not excavate, conservation concerns for this species may be addressed through retaining dead limbs and snags from the habitats in which it occurs; through protecting oak woodland landscapes from disturbance and fragmentation in order to assure adequate recruitment of new oaks and other trees; and through restoring riparian habitats and increasing the presence of oaks and other large trees, particularly when these corridors can be linked throughout the region.
Hutton’s Vireo (Vireo huttoni)
A resident species in this region, which appears to expand it geographical and habitat range outside of the breeding season, these insectivorous birds prefer woodlands with evergreen trees, such as live oaks, and riparian corridors. This species generally nests in mountainous regions west (and east) of the Central Valley floor. Conservation concerns may be addressed by maintaining the abundance of evergreen tree species in woodlands and forests, as well as through restoring or enhancing the coverage and abundance of these trees.
GRASSLAND AND PRAIRIE
SHRUBLAND AND CHAPARRAL
Wrentit (Chamaea fasciata)
Considered a Yellow List Species on Audubon’s WatchList 2007, indicating that the species is rare or declining over all or a significant portion of its range. The Wrentit’s distribution is limited to the west coast of North America. In Yolo County, the Wrentit is considered a common year-round resident of chaparral and riparian habitats, found mostly in the northwestern corner of the county in the Coast Range foothills. This species requires a somewhat dense shrub understory for breeding habitat. Wrentit populations may be negatively impacted by isolation and fragmentation of shrublands due to human development, prescribed fires causing mortality and introduced plants and animals that decrease available nest habitat and increase nest predation. Maintenance and protection of large undisturbed tracts of chaparral and riparian scrub habitat with dense vegetative cover may be necessary to ensure the long-term viability of this species.
California Thrasher (Toxsostoma redivivum)
Considered a Yellow List Species on Audubon’s WatchList 2007, indicating that the species is rare or declining over all or a significant portion of its range. Breeding Bird Survey Data show a decrease in California Thrasher populations over the past 25 years. These data are mirrored by parallel declines noted from BBS data for Mountain Quail and Wrentits, birds that also are dependent on large tracts of dense undisturbed chaparral habitat. The California Thrasher is endemic to California and is found primarily in chaparral and riparian habitats of the coastal and foothills regions. The California Thrasher is a breeder and uncommon permanent resident of chaparral and riparian habitats of the Coast Range foothills in the northwestern corner of Yolo County. Habitat fragmentation, modification and loss are the primary threats to California Thrasher populations. Maintenance and protection of large undisturbed tracts of chaparral and riparian scrub habitat with dense vegetative cover may be necessary to ensure the long-term viability of this species.
Sage Sparrow (Amphispiza belli)
The coastal subspecies, Bell’s Sage Sparrow (Amphispiza belli belli), is considered a Yellow List Species on Audubon’s WatchList 2007, indicating that this subspecies is rare or declining over all or a significant portion of its range. The Bell’s Sage Sparrow has also been listed as a Species of Special Concern in California. This bird is an uncommon primarily non-migratory resident of coastal scrub and dry chaparral habitats in the Coast Ranges of California. In Yolo County, sage sparrows are breeding residents in chaparral habitats of the coastal foothills in the northwestern portion of the county. The Bell’s Sage Sparrow is threatened by habitat fragmentation and loss, habitat conversion, and disturbance around the nest sites. This is due primarily to livestock grazing, fire suppression, off-road vehicle use and human development. Maintenance and protection of large undisturbed tracts of chaparral and scrub habitat with dense vegetative cover may be necessary to ensure the long-term viability of this species.
Mountain Quail (Oreortyx pictus)
Considered a Yellow List Species on Audubon’s WatchList 2007, indicating that the species is rare or declining over all or a significant portion of its range. The Mountain Quail is an uncommon year-round resident of chaparral and scrub habitats of the Cascades, Coast Ranges and Sierra Nevada. It occurs primarily at elevations of 700 – 3000 meters. The Mountain Quail is found locally in the Coast Range foothills of northwestern Yolo County. The greatest threat to Mountain Quail populations appears to be habitat destruction due to human development. Conversion of chaparral and scrub habitats leads to habitat fragmentation and loss. In addition, grazing and agriculture may damage or destroy habitat. Maintenance and protection of large undisturbed tracts of chaparral and scrub habitat with dense vegetative cover may be necessary to ensure the long-term viability of this species.
Conservation Corner - January 2017
To many people, conservation issues are best appreciated for their local significance. Changes in the abundance of birds can provide such meaning. Yolo Audubon Society’s Christmas Bird Count, centered on Putah Creek, provides forty-six consecutive years of records of bird numbers, which Steve Hampton has compiled onto a spreadsheet. This article will point to trends for several species from the Christmas Count results, and relate them to conservation issues.