Western Birds Journal

Volume 35, No. 3

Published July 1, 2004

Issue description

Volume 35, number 3 of Western Birds, published 2004

Articles

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    LAIRD A. HENKEL (Author)

    SEASONAL ABUNDANCE OF MARINE BIRDS IN NEARSHORE WATERS OF MONTEREY BAY, CALIFORNIA

    Monterey Bay, California, is a site of regional significance for marine birds. I studied the seasonal abundance of marine birds within 1 km of shore in Monterey Bay during 1999 and 2000. Total bird abundance was greatest during spring and fall migration, whereas diversity was greatest during winter. Species assemblages were fairly consistent by season in both years, but three species were more abundant during summer and fall 2000 than during those seasons in 1999. This increased abundance may have been a response to reduced prey availability outside the study area, related to sea-surface temperature in spring 2000 being higher than in spring 1999. The mean density of all species (363 birds/km²) was considerably greater than the density reported for Monterey Bay as a whole, indicating that the nearshore environment should receive unique consideration in studies of the abundance and distribution of marine birds.

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    DOUG FAULKNER (Author)

    GLOSSY IBIS RECORDS FOR COLORADO AND NEIGHBORING STATES

    The Glossy Ibis (Plegadis falcinellus) first arrived in the New World in the early 1800s. During the twentieth century, this species expanded its breeding range rapidly, extending as far west as Louisiana. Vagrants have occurred throughout the Great Plains and even to California. Colorado’s 35 documented Glossy Ibis through 2002 are more than in any neighboring state by at least 40%. These records represent primarily single birds during spring migration; however, recent records include some of multiple birds, as well as one in fall. Timing of these records, the birds’ association with flocks of the White-faced Ibis (P. chihi), and lack of nesting sites in Colorado suggest that the Glossy Ibis is continuing its migration outside of Colorado. The increased number of records, increased number of birds per record, and recent reports of potential hybrids in Oklahoma and Colorado also suggest that the Glossy Ibis may be expanding its breeding range west into the Great Plains.

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    JENNIFER D. WHITE, THOMAS GARDALI (Author)

    LOW INCIDENCE OF COWBIRD PARASITISM ON SWAINSON’S THRUSHES IN CENTRAL COASTAL CALIFORNIA

    We found a low incidence of Brown-headed Cowbird (Molothrus ater) parasitism (4%; 9/224 nests) of Swainson’s Thrush (Catharus ustulatus) in central coastal California despite the high rates (33%) reported here for Wilson’s Warbler (Wilsonia pusilla). Both species nested primarily in blackberry shrubs and ferns in similar proportions and at similar heights. Thrush nests were significantly better concealed than warbler nests. In both the thrush and warbler, however, concealment of parasitized and unparasitized nests did not differ. The number of potential cowbird perches was not significantly greater at warbler nests or at parasitized nests of either species. No cowbirds fledged from thrush nests; in thrush nests cowbird nestlings observed were last seen at ages of 4 to 7 days, whereas thrush nestlings fledged. At our study sites Swainson’s Thrushes fed nestlings a variety of fruit; this partially frugivorous diet may not be suitable for cowbird nestlings, leading to their death. Parasitism significantly reduced the thrushes’ clutch size, number of nestlings, and number of fledglings. In four thrush nests experimentally parasitized with real cowbird eggs we observed no rejection response, suggesting that ejection of cowbird eggs is not responsible for the low rate of parasitism observed at our sites. It is unclear why Swainson’s Thrushes are parasitized infrequently at our sites, but we suggest that nest concealment may be partly responsible. We did not study behavioral differences between Swainson’s Thrush and Wilson’s Warbler, but such differences may contribute to the observed difference in parasitism rates.

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    T. WILL RICHARDSON (Author)

    NOTES: EXPANSION OF THE BREEDING RANGE OF THE BUFFLEHEAD IN CALIFORNIA

    Historically, the Bufflehead (Bucephala albeola) has maintained a small, isolated breeding population in extreme northeastern California, restricted to parts of Butte, Lassen, Modoc, Plumas, Shasta, and Tehama counties (Figure 1, inset). Prior to 1996, there were no known breeding records from California south of Lake Almanor, Plumas County (San Miguel 1998). However, the Bufflehead occasionally breeds outside of its principal range, and extralimital records to the south have been recorded recently in Colorado (Ringelman and Kehmeier 1990), Minnesota (Mattsson 1986), South Dakota (Whitt 1999), and California (San Miguel 1998, Patten et al. 2003). San Miguel (1998) described three cases of extralimital breeding in California from 1996, and Patten et al. (2003) reported a brood found on the Salton Sea in 1999. These successful breeding efforts were discovered in a variety of habitats in Inyo, Los Angeles, Riverside, and Tulare counties, up to 850 km south of the species’ traditional breeding range (San Miguel 1998).

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    MARK E. SEAMANS, JEFFERY CORCORAN, ANGELA REX (Author)

    NOTES: SOUTHERNMOST RECORD OF A SPOTTED OWL × BARRED OWL HYBRID IN THE SIERRA NEVADA

    In the summer of 2003, we located a territorial hybrid between the Spotted Owl (Strix occidentalis) and the Barred Owl (S. varia) in the Rubicon River watershed, Placer County, in the Sierra Nevada (latitude 38° 57′ N, longitude 120° 29′ W). The individual was located in the same general area on six occasions, and it may have displaced a pair of Spotted Owls from this area. We trapped Spotted Owls and color-banded them in this area each year from 1993 to 2002. We found the pair of Spotted Owls that occupied this area in 2002 defending a different area 4.5 km to the southwest in 2003. On four occasions, we found the hybrid owl roosting in a natural cavity in a Black Oak (Quercus kelloggii). This cavity had been used as a nest site by Spotted Owls in 3 of the past 10 years.

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    PHILIP UNITT (Author)

    NOTES: THE SOUTHERN LIMIT IN CALIFORNIA OF THE NORTHERN PYGMY-OWL

    In northern and central California, the Northern Pygmy-Owl (Glaucidium gnoma) is widespread in both the Coast Ranges and Sierra Nevada. In southern California it occurs in the Transverse Ranges from Santa Barbara County (Lehman 1994) east through the San Gabriel and San Bernardino mountains. In the Peninsular Ranges of Riverside, Orange, and San Diego counties, however, evidence for the species is tenuous at best. Intensive study of San Diego County 1997–2002, toward a bird atlas for that area, failed to find the species and suggests that the few past reports were in error.

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    Jeff .N. Davis (Author)

    BOOK REVIEW: Important Bird Areas of California: by Daniel S. Cooper. 2004. Audubon California. 286 pages, 3 tables, 8 maps, 3 appendixes. Paperback. Available for $19.99 + $5.00 shipping and handling through Audubon California, 11340 Olympic Blvd., Suite 209, Los Angeles, CA 90064.

    California is one of the richest and most threatened reservoirs of biodiversity on earth (Conservation International 2004: www.biodiversityhotspots.org/xp/Hotspots/california_floristic/ So it should come as no surprise that on a global scale the state itself may be viewed as an important bird area, if not for its wealth and diversity of bird species and subspecies, many of which are in jeopardy, then for its high level of endemism (Stattersfield et al. 1998). Inevitably, some areas within the state are more important for birds than others—but only recently has there been a focused effort to identify and describe these areas, let alone protect them.

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    BRUCE DEUEL (Author)

    FEATURED PHOTO: PRELIMINARY NOTES ON THE IDENTIFICATION OF CACKLING AND CANADA GEESE

    Now that the American Ornithologists Union (A.O.U.) has split the Canada Goose (Branta canadensis) into two species (Banks et al. 2004) field birders are faced with the not inconsiderable problem of telling the two apart. This identification issue is especially challenging for birders in the West, where a number of races of both species occur. Of the four subspecies that now constitute the Cackling Goose (Branta hutchinsii), the nominate Richardson’s Cackling Goose (B. h. hutchinsii) is almost unknown west of the Rocky Mountains (A.O.U. 1957), while the diminutive and very dark Cackling Goose proper (B. h. minima) is unlikely to be mistaken for any form of the Canada Goose. The Aleutian Cackling Goose (B. h. leucopareia) has features, such as a complete white ring at the base of the black neck, that make identification of most individuals straightforward.