Western Birds Journal

Volume 42, No. 2

Published April 1, 2011

Issue description

Volume 42, number 2 of Western Birds, published 2011

Articles

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    EDWARD R. PANDOLFINO, MARK P. HERZOG, STACIE L. HOOPER, ZACHARY SMITH (Author)

    WINTER HABITAT ASSOCIATIONS OF DIURNAL RAPTORS IN CALIFORNIA’S CENTRAL VALLEY

    The wintering raptors of California’s Central Valley are abundant and diverse. Despite this, little information exists on the habitats used by these birds in winter. We recorded diurnal raptors along 19 roadside survey routes throughout the Central Valley for three consecutive winters between 2007 and 2010. We obtained data sufficient to determine significant positive and negative habitat associations for the White-tailed Kite (Elanus leucurus), Bald Eagle (Haliaeetus leucocephalus), Northern Harrier (Circus cyaneus), Red-tailed Hawk (Buteo jamaicensis), Ferruginous Hawk (Buteo regalis), Rough-legged Hawk (Buteo lagopus), American Kestrel (Falco sparverius), and Prairie Falcon (Falco mexicanus). The Prairie Falcon and Ferruginous and Rough-legged hawks showed expected strong positive associations with grasslands. The Bald Eagle and Northern Harrier were positively associated not only with wetlands but also with rice. The strongest positive association for the White-tailed Kite was with wetlands. The Red-tailed Hawk was positively associated with a variety of habitat types but most strongly with wetlands and rice. The American Kestrel, Northern Harrier, and White-tailed Kite were positively associated with alfalfa. Nearly all species were negatively associated with urbanized landscapes, orchards, and other intensive forms of agriculture. The White-tailed Kite, Northern Harrier, Red-tailed Hawk, Ferruginous Hawk, and American Kestrel showed significant negative associations with oak savanna. Given the rapid conversion of the Central Valley to urban and intensive agricultural uses over the past few decades, these results have important implications for conservation of these wintering raptors in this region.

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    MIKE M. STAKE, KELLY SORENSON (Author)

    TRENDS IN RIPARIAN SONGBIRDS BANDED AT BIG SUR, CENTRAL CALIFORNIA COAST

    We assessed trends in rates of capture of eight riparian songbirds mist-netted over 17 years (1993–2009) at Big Sur, on the central California coast. The Warbling Vireo (Vireo gilvus) and Yellow Warbler (Dendraica petechia) declined significantly, whereas the Swainson’s Thrush (Catharus ustulatus) showed a nearly significant increase. Rates of capture of the Willow Flycatcher (Empidonax traillii), Wilson’s Warbler (Wilsonia pusilla), Common Yellowthroat (Geothlypis trichas), Yellow-breasted Chat (Icteria virens), and Black-headed Grosbeak (Pheucticus melanocephalus) were stable. Negative trends for the Warbling Vireo and Yellow Warbler were particularly strong for hatching-year birds, indicating that factors acting in the breeding season were responsible for declines. We captured high ratios of transients to local adults, and at Big Sur trends for some of these species are associated more with populations breeding in other regions. However, in the Swainson’s Thrush and Wilson’s Warbler, we observed significant increases in local adults and local hatching-year birds, indicating the importance of local riparian habitat for some species at Big Sur.

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    MATTHEW TIMMER, DAVID L. SUDDJIAN, SUSAN LAMBRECHT, SHANNON BROS-SEEMANN (Author)

    NESTING SUCCESS OF THE YELLOW WARBLER IN A DISTURBED RIPARIAN FOREST IN COASTAL CALIFORNIA

    Widespread decline of Yellow Warbler populations in California has led to increased interest in their conservation and management. However, because the species is now rare throughout much of its historic range in the state, there is relatively little demographic information about it. Predation and Brown-headed Cowbird parasitism are cited as causing declines, but their effects are poorly quantified. To address this information need, in 2008 we investigated the reproductive biology of the Yellow Warbler along the Pajaro River in Santa Cruz and Monterey counties, California, where the species is still relatively abundant. We examined predation and parasitism pressures by monitoring nests and recording reproductive success. In this heavily disturbed area, the Yellow Warbler’s nest success was very low (10%), revealing that one of the larger populations of this species remaining in the region may be threatened.

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    SCOTT JENNINGS, RENÉE L. CORMIER, THOMAS GARDALI, DAVID PRESS, WILLIAM W. MERKLE (Author)

    STATUS AND DISTRIBUTION OF THE BARRED OWL IN MARIN COUNTY, CALIFORNIA

    Marine County, California, is the southern limit of the range of the Northern Spotted Owl (Strix occidentalis caurina), listed as threatened by the U.S. Fish and Wildlife Service. The density of the Marine population of the Northern Spotted Owl is unusually high, the population breeds in unique habitat associations, and it is genetically isolated from other Spotted Owl populations. Unlike elsewhere in the Northern Spotted Owl’s range, habitat loss to logging is not an issue in Marine County. The Barred Owl (Strix varia) has been detected in Marine County only since 2002 and may pose a threat to the Northern Spotted Owl through competition and/or interbreeding. We amassed information on the distribution and abundance of the Barred Owl in Marine County via published literature, by consulting local birders, and primarily through data we obtained during our monitoring of the Northern Spotted Owl in Marine County. Monitoring, continuous since 1996, provides an opportunity for an evaluation of the effect of the Barred Owl invasion on the Northern Spotted Owl there. We estimate the county’s current population of the Barred Owl at four to seven individuals, including one territorial pair and a single territorial male. We documented two nestings, with four young fledged. Two pairs of the Northern Spotted Owl have been displaced from territories. These results are of concern for an otherwise stable population of the Northern Spotted Owl.

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    DANIEL S. COOPER (Author)

    TWO RECENT RECORDS OF THE CLAPPER RAIL FROM THE BALLONA WETLANDS, LOS ANGELES COUNTY, CALIFORNIA

    I report on two recent records of the Clapper Rail (Rallus longirostris) from the Ballona Wetlands at Playa del Rey in Los Angeles County, including the first well-documented report in the county over 40 years, from a site where a population persisted into the 1950s. On 25 August 2008, two biological consultants (A. Gutierrez and R. Woodfield, with Merkel and Associates, San Diego) sampling fish in a tidal channel at the Ballona Wetlands just south of Ballona Creek spotted a bird they suspected was a Clapper Rail. On 21 January 2010 Gutierrez wrote to me, “on August 25, 2008 a Light-footed Clapper Rail was observed foraging along the eastern waterline of a channel in the pickleweed of the Ballona Wetlands. The observation occurred at 11:30 A.M. on a clear day, with no wind, a temperature of 70 °F, and during a low tide of 3.2 ft mean lower low water. Although it was a low tide, the water level was fairly high due to the tide being subject to muting and lag from the presence of tide gates at the Ballona Wetland. The Clapper Rail walked the edge of the high waterline from south to north and then back to the south, weaving through the pickleweed. After approximately 5 minutes, the Clapper Rail flew to the west shore of the channel and proceeded out of sight into the dense pickleweed.”

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    JACK J. WITHROW, DAVID W. SONNEBORN (Author)

    IMPORTANT RECENT BIRD RECORDS FROM ATTU ISLAND, ALASKA

    During recent field work for the University of Alaska Museum on Attu Island, Aleutian Islands, Alaska, we obtained important specimens of three species: North America’s first of the Chinese Pond-Heron (Ardeola bacchus), first of the Solitary Snipe (Gallinago solitaria), and third of the Pin-tailed Snipe (G. stenura). These records expand our knowledge of the diverse Asian avifauna that passes through the western Aleutians in spring.

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    PETER PYLE (Author)

    BOOK REVIEW: Paseriformes del Occidente de México: Morfometría, Datación y Sexado

    Molt is a difficult topic for most ornithologists to comprehend, yet it is a vital component of almost all aspects of avian natural history. Conservation of birds will necessitate protecting locations and habitats for molt, but because birds become very retiring while molting we have almost no understanding of their requirements for this process on a species-specific basis. Our ability to determine the age and sex of birds, essential to tracking population demography, also depends almost entirely on an understanding of molt. In North America and Europe we are slowly making progress on this subject, but for the Neotropical Region we are still in the dark. For the 2006 North American Ornithological Congress in Veracruz, Mexico, I reviewed the literature and my unpublished notes and calculated that we had some (but often very little) information on molt for only 24% of 934 species of resident neotropical landbirds, and for only 8% of the species did we have information on both extent and timing of molts.

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    DOUGLAS E. WEIDEMANN, FLOYD E. HAYES (Author)

    FEATURED PHOTO: ATTRACTION OF BIRDS TO HUMAN FOOD IN YOSEMITE NATIONAL PARK, CALIFORNIA

    We studied the attraction of birds to human food at 50 picnic sites in Yosemite National Park, California, during summer 2009. At each site we made two 10-minute point counts, one in the morning, when human food was never present, and one at midday, when human food was always present. Eight of 26 species fed on human food. We found fewer individuals and species during counts with human food at high-elevation sites and more individuals and species during counts with human food at low-elevation sites. Significantly more Steller’s Jays (Cyanocitta stelleri) and significantly fewer Mountain Chickadees (Poecile gambeli) occurred during counts with human food.