LONG-EARED OWL (Asio Otus) Kevin Hunting
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II SPECIES ACCOUNTS Andy Birch PDF of Long-eared Owl account from: Shuford, W. D., and Gardali, T., editors. 2008. California Bird Species of Special Concern: A ranked assessment of species, subspecies, and distinct populations of birds of immediate conservation concern in California. Studies of Western Birds 1. Western Field Ornithologists, Camarillo, California, and California Department of Fish and Game, Sacramento. Studies of Western Birds No. 1 LONG-EARED OWL (Asio otus) Kevin Hunting Criteria Scores Population Trend 10 Range Trend 5 Population Size 7.5 Range Size 0 Endemism 0 Population Concentration 0 Threats 10 Current Breeding Range Historic Breeding Range County Boundaries Water Bodies Kilometers 100 50 0 100 Current and historic (ca. 1944) breeding range of the Long-eared Owl in California. Occurs very locally within the mapped range, particularly in the southern deserts and densely forested areas. Essentially extirpated from the entire floor of the Central Valley and locally on the southern coast; numbers have declined at least moderately overall. Occurs more widely in lowland areas of the state during migration and winter. 234 Studies of Western Birds 1:234–241, 2008 Species Accounts California Bird Species of Special Concern SPECIAL CONCERN PRIORITY ft (3200 m) in the White Mountains, Mono County. They considered the species overall to be Currently considered a Bird Species of Special “common” to “abundant locally” and noted cen- Concern (breeding), priority 3. Included on both ters of abundance in the northeastern Great Basin prior special concern lists (Remsen 1978, 2nd region, the central interior valleys, and the San priority; CDFG 1992). Diegan (southern coast) district. They reported an apparent decline in “late years,” which they REEDING IRD URVEY TATISTICS B B S S indicated likely reflected mainly the clearing of FOR CALIFORNIA lowland habitat for farming. Data inadequate for trend assessment (Sauer et Northeastern California. Breeding was con- al. 2005). firmed near Dewitt, Lassen County, and at Mono Lake, Walker Creek, and Convict Creek, Mono GENERAL RANGE AND ABUNDANCE County; records of immatures at Goose Lake, Modoc County, in early June are strongly sug- Distributed broadly throughout the Holarctic. gestive of breeding (Grinnell and Storer 1924, In North America, breeds across central Canada Grinnell and Miller 1944, Gaines 1992, MVZ and south interruptedly through northern Baja specimens and egg sets). California in the West and Virginia in the East Sierra Nevada. Little is known of prior status (Marks et al. 1994). It may winter throughout in the Sierra, though breeding was documented the breeding range, but northernmost popula- at Yosemite Valley, Mariposa County (Grinnell tions usually are migratory; disperses south to the and Storer 1924). A July 1898 observation of the southeastern United States and southern Mexico species at Mt. Tallac, just south of Lake Tahoe, El (Howell and Webb 1995). Nomadism, in response Dorado County (Orr and Moffitt 1971), is sug- to prey availability and abundance, is documented gestive of breeding. in Europe but is not clearly understood in North Central Valley. Historic status in this region America (Voous 1988, Korpimäki 1992, Marks likewise is poorly known. Tyler (1913) reported et al. 1994). No population estimate is available confirmed breeding along the San Joaquin River for North America, but the species is considered and near New Hope school, Fresno County, and “relatively common” in the western United States described this owl as “nowhere . abundant” (Marks et al. 1994). near Fresno in the San Joaquin Valley. Specimens In North America, has been divided into two of adults and immatures collected in June along subspecies, A. o. wilsonianus in the East and A. o. Butte Creek near Chico, Butte County, also sug- tuftsi in the West (AOU 1957), but the validity gest local nesting (MVZ specimens). of this distinction is questioned given the species’ Central and southern coast. Grinnell and highly nomadic nature (Marks et al. 1994, Haas Wythe (1927) described this owl as a sparse 2004). and local resident in coastal portions of the San Francisco Bay region. Willett (1933) character- SEASONAL STATUS IN CALIFORNIA ized it as a “fairly common” resident of the foot- Occurs in the state year round, although seasonal hills and lowlands of coastal southern California. status varies regionally; breeds from February Breeding was confirmed at the Russian River through July (Marks et al. 1994, Haas 2004). near Windsor, Sonoma County; Novato, Marin Grinnell and Miller (1944) noted “markedly County; Alameda, Alameda County; Berryessa irregular wanderings of individuals and groups,” and Betabel, Santa Clara County; Santa Cruz, but it is unclear to what extent this reflects local Santa Cruz County; Paicines and San Juan, San movements in California or influxes from outside Benito County; Hastings Natural History Reserve the state. and near Carmel Valley, Monterey County; Paso Robles and Shandon, San Luis Obispo County; HISTORIC RANGE AND ABUNDANCE Goleta and Aliso Canyon, Santa Barbara County; near Redlands and Yucaipe Valley, San Bernardino IN CALIFORNIA County; near Santa Paula, Santa Clara River, Grinnell and Miller (1944) described the Long- Sherwood Lake, and Nordhoff, Ventura County; eared Owl as breeding the length and breadth of Pasadena, Placerita Canyon near Newhall, San the state east of the northern humid coastal region Fernando Valley, and Santa Catalina Island, Los and from sea level to 7000 ft (2134m), but noted Angeles County; Pedley and Beaumont, Riverside an exceptionally high elevation record of 10,500 County; Alamitos and near La Habra, Orange Long-eared Owl 235 Studies of Western Birds No. 1 County; and San Luis Rey River near Bonsall, and Fitton (1998) described the Long-eared Owl Escondido, and Lakeside, San Diego County as a “widespread breeder” recorded in 33 (45%) (Grinnell and Wythe 1927; Willett 1912, 1933; of 74 atlas blocks in the Glass Mountain area of Grinnell and Miller 1944; Sibley 1952; Bloom Mono County. To the east and south, the species 1994; Lehman 1994; Burridge 1995; Roberson is an “uncommon” resident in the White-Inyo 2002; CAS, MVZ, and WFVZ egg sets). Birds col- Range; nesting has been documented in the lected in June on Mount Pinos, Ventura County, White Mountains as high at 9500 ft (2896 m) and in July (including immatures) at Round Valley at Cottonwood Creek, Mono County (Johnson in the San Jacinto Mountains, Riverside County, and Cicero 1986), and an individual was seen in likely reflect breeding in the higher mountains of July at 10,400 ft (3170 m) in Silver Canyon, Inyo southern California (MVZ specimens). County (T. & J. Heindel in litt.). Southern deserts. This owl was documented Cascade Range and Sierra Nevada. This owl has breeding at Bishop, Inyo County, and Victorville, been recorded in summer at Cutter Butte, Shasta San Bernardino County; May–June records County, in the Cascades (J. Winter in litt.). Siegel from Walker Creek near Olancha and the Argus and DeSante (1999) considered this species a Mountains, Inyo County, and from Essex, San “rare” resident and breeder on the west slope of the Bernardino County, also suggest local breeding in Sierra and a locally “uncommon” summer resident this region (Grinnell and Miller 1944, MVZ and on the east slope. Nesting was confirmed (young WFVZ specimens or egg sets). calling) in the northern Sierra near Blakeless Creek, Plumas County, in 1984, and owls were RECENT RANGE AND ABUNDANCE recorded at Duncan Peak Lookout, Placer County; Gerle Creek Campground, El Dorado County; IN CALIFORNIA and Charity Valley, Alpine County (J. Winter in Limited historical information on the Long-eared litt.). In the Yosemite area, Gaines (1992) reported Owl, particularly for the Central Valley, Sierra confirmed breeding on the west slope at Ackerson Nevada, and southern deserts, makes it difficult Meadow, Tuolumne County, and pairs during to characterize subsequent population trends. the breeding season at Swamp Lake, Tuolumne The range has retracted locally on the southern County, and Henness Ridge, Mariposa County. coast and apparently more broadly in the Central There also are summer records of birds at Crane Valley. The substantial loss of riparian habitat in Flat and Peregoy Meadow, Mariposa County (J. the Central Valley (87%; GIC 2003) and coastal Winter and J. Davis in litt.). This owl is a sum- southern California (95%–97%; Faber et al. mer resident along the South Fork Kern River, 1989) has almost certainly resulted in popula- Kern County, at the base of the southern Sierra (J. tion declines. Recent breeding season records for Sterling pers. comm.) Humboldt County and expanded knowledge of Central Valley. Limited available information the range in the Mojave and Colorado deserts suggests this owl today is a very scarce and likely reflect increased observer coverage rather irregular breeder in the Central Valley. Records than true range expansions (see map). for the Sacramento Valley include one of a nest Northwestern California. Surveys for the with young in the Yolo Bypass, Yolo County, in Humboldt County breeding bird atlas found 1961 (Yolo Audubon Society 2004) and ones for Long-eared Owls in 11 scattered blocks in the Sacramento County of a nest with young in an southern half of the county, mainly in the interior orchard in Rio Linda in 1974 (fide T. Manolis (Hunter et al. 2005). Prior records for the region and C. Conard), of an adult hit by a car near representing possible breeding birds extend from Folsom Dam in July 1979 (fide T. Manolis and Bald Hills, Humboldt County, south to Willets, C. Conard), and of a nest in an Interior Live Mendocino County (Harris 2005). Oak (Quercus wislizenii) at Goethe Park on the Northeastern California. This region currently American River Parkway in 2002 (S. Flannery fide is perhaps the center of abundance for this species C. Conard). in California. It nests in the Honey Lake Valley, Just west of the San Joaquin Valley, nests Lassen County, but appears to have declined were found in 2005 in a juniper (Juniperus sp.) in numbers in recent years (T.