ARCHIVED REPORTS_1993_1 - Laserfiche WebLink

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u Li u 11 L Burrowing Owl Background. The burrowing owl is identified as a state species of special concern; nesting owls also are protected under Section 3503.5 of the California Fish and Game Code (50 CFR, Part 21 and 50 CFR, Part 100) and the federal Migratory Bird Treaty Act (16 USC 703). Burrowing owls were formerly a common, permanent resident throughout much of California, but population declines were noticeable by the 1940s (Grinnell and Miller 1944) and have continued to the present (DeSante pers. comm.). Burrowing owls prefer open, dry, and nearly level grassland habitat where they feed on insects, small mammals, and reptiles. The owl lives and breeds in burrows, typically in abandoned ground squirrel colonies. The breeding season usually extends from late February through August. Burrowing owls often nest in roadside embankments, on levees, and along irrigation canals. They are more diurnal than most owls and can often be observed during the day standing outside the entrance to their burrows. Ground squirrel control measures and the conversion of grasslands to agriculture are the primary factors responsible for the species' decline (Zarn 1974). Status in the Project Area. Surveys for burrowing owls were combined with kit fox den surveys because both species generally occur in similar habitats. Biologists looked for signs of owl presence, such as feather, pellets, or whitewash, at burrows and elsewhere on the site. No burrowing owls or signs of their activity were observed at the project site. A burrowing owl was observed during the February survey in a grainfield approximately 1 mile southwest of the project site. Although burrowing owls are not currently using the project site, the annual grasslands are considered suitable foraging and denning habitat. California Horned Lark Background. The California horned lark is one of eight subspecies that breed in California and is resident along a large area of the California Coast Range and the San Joaquin Valley, from Humboldt County, south to Baja California (Behle 1942). The California horned lark is an abundant species in grassland habitats throughout San Joaquin County and nearby Contra Costa County. Horned larks nest in dry grasslands and rangelands that have low, sparse cover and feed on seeds of grains, forbs, and grasses and on small insects (Bent 1942). California horned lark populations have declined in certain areas due to habitat loss to urban and agricultural development. Declines in coastal breeding populations of this subspecies are of particular concern (Rorabaugh pers. comm.). Status in the Project Area. Several horned larks were observed in annual grasslands at the project site in February 1993. Annual grasslands at the project site provide foraging and nesting habitat for the California horned lark. Loggerhead Shrike Background. The loggerhead shrike is a widespread breeding species in North America (American Ornithologists Union 1957). Shrike populations in the western United States fluctuated between 1955 and 1979 but now appear stable (Morrison 1979, Fraser and Luukkonen 1986). The species is common in open grasslands throughout the Central Valley. The shrike inhabits grasslands, agricultural lands, open shrublands, and open woodlands (Bent 1950). Shrikes nest in low trees, dense shrubs, and vines and feed on insects, small reptiles, and small mammals. i ER -93-1 -39- (9-27-93)