Western Birds Journal

Volume 51, No. 1

Published January 1, 2020

Issue description

Volume 51, number 1 of Western Birds, published 2020

Articles

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    DANIEL S. SINGER, THOMAS A. BENSON, GUY McCASKIE, JUSTYN STAHL (Author)

    THE 43RD ANNUAL REPORT OF THE CALIFORNIA BIRD RECORDS COMMITTEE: 2017 RECORDS

     From its last report through 2017 the California Bird Records Committee reached decisions on 178 records involving 176 individuals of 71 species and two species groups, endorsing 154 records of 153 individuals. Th fist accepted state records of Band-rumped Storm-Petrel (Hydrobates castro), Kermadec Petrel (Pterodroma neglecta), Eurasian Wryneck (Jynx torquilla), and Citrine Wagtail (Motacilla citreola) are outlined in this report. Thse additions plus additions in 2018 bring California’s total list of accepted species to 673, of which 11 represent established introductions. Other notable records detailed in this report include the state’s second Ross’s Gull (Rhodostethia rosea) and third Swallow-tailed Gull (Creagrus furcatus).

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    JEANNE TINSMAN, MARTIN MEYERS (Author)

    NEVADA BIRD RECORDS COMMITTEE REPORT FOR 2018

     In 2018, the Nevada Bird Records Committee reviewed 56 reports from the period 23 May 1981–23 July 2018; 46 were endorsed. No new species were added to the state list, which stands at 489 species. Th review list underwent a major revision in August 2018, reducing the number of full species requiring review from 141 to 108; two additional subspecies remain on the list.

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    ROBERTO CARMONA, GERARDO MARRÓN, SERGIO ÁGUILA, ABIGAIL RIVAS, SERGIO FLORES RAMÍREZ, HÉCTOR REYES BONILLA (Author)

    POPULATION ASSESSMENT OF BELDING’S YELLOWTHROAT (GEOTHLYPIS BELDINGI) AT SAN IGNACIO OASIS, BAJA CALIFORNIA SUR, MEXICO

     Belding’s yellowthroat (Geothlypis beldingi) is an endangered species endemic to the southern half of the Baja California Peninsula. Thre are no current estimates of the species’ population, crucial to scientifially based management for its conservation. Threfore, we assessed the species’ population at one of its major sites, the oasis of San ignacio. during the reproductive season, the density of birds reached around 17 individuals per hectare, representing an estimated total population of about 250 birds. Previous estimates of the abundance of Belding’s yellowthroat are inconsistent, emphasizing the need for a re-evaluation with more robust methods. in addition, we recorded a signifiant decrease in the number of males of the species immediately aftr the reproductive season, which suggests that these birds may disperse immediately aftr the breeding season, possibly to avoid competition with their conspecifis. if so, this has important implications for this bird’s spatial population structure.

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    MYRNA PEARMAN, LEO DE GROOT, GEOFFREY L. HOLROYD, STEPHANIE THUNBERG (Author)

    EARLIER SPRING ARRIVAL OF THE MOUNTAIN BLUEBIRD IN CENTRAL ALBERTA, CANADA

     Much attention has been given to the topic of bird phenology in response to climate change. While strong evidence supports a general pattern of advancement in spring migrants’ arrival dates with warming temperatures, the mechanisms underlying these changes are not clearly understood. We summarize the spring arrival of the Mountain Bluebird (Sialia currucoides) in central alberta from 58 years of data and examine the inflence of temperature and snow cover on the patterns of arrival. We hypothesized that a signifiant advance in the Mountain Bluebird’s fist arrival date was related to weather variables. in central alberta, March temperatures increased, and fist arrival dates for the Mountain Bluebird advanced
    0.33 days per year from 1961 to 2018 or 19 days over the 58 years. However, temperatures on the date of arrival have cooled slightly (2.8 °C) over the study period, and snow depth on the date of arrival decreased slightly (1.5 cm) over the study period, which may inflence early migrants’ opportunities for foraging. although Mountain Bluebirds have arrived at our central alberta study area considerably earlier over the past decades, temperatures and snow depth have been highly variable, suggesting that the species is likely responding to multiple cues that inflence its arrival dates. Given the Mountain Bluebird’s migratory nature, environmental and behavioral stimuli en route to breeding areas likely exert considerable inflence on arrival dates.

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    PHILIP UNITT, LORI HARGROVE, KEVIN B. CLARK (Author)

    OVERLAP OF MOLT AND FALL MIGRATION OF THE WESTERN TANAGER AND WARBLING VIREO IN SOUTHERN CALIFORNIA

     It is an axiom of ornithology that the energy-demanding phases of a small bird’s life cycle, such as molt and migration, are segregated temporally (e.g., Newton 2008). Ths principle applies so widely that exceptions to it may be instructive. Here we report apparent exceptions in two species, the Warbling Vireo (Vireo gilvus) and Western Tanager (Piranga ludoviciana), on the basis of recent specimens from southern California.

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    MITCHEL D. BOSMA, HAYLEY H. ROSS, ROBERT B. DOUGLAS (Author)

    NORTHERN PYGMY-OWL PREDATION ON AN ADULT CALIFORNIA QUAIL

    The Northern Pygmy-Owl (Glaucidium gnoma) opportunistically hunts and feeds on songbirds, small mammals, reptiles, and insects (Merrill 1888, Holman 1926, Brock 1958, Bull et al. 1987). Diet studies indicate that although pygmy-owls feed primarily on species smaller than themselves, they also take species with body masses similar to or slightly larger than themselves (70–100 g; Giese and Forsman 2003). Occasionally they take even larger prey (i.e. ≥ twice body mass, such as the Northern Flicker (Colaptes auratus; Holt and Leroux 1996).

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    DESMOND E. SIEBURTH (Author)

    A REVIEW OF WESTERN BIRD RECORDS COMMITTEE WEBSITES

     Every state and most provinces in the western United States and Canada have a bird records committee (BRC). Th committees receive thousands of reports of rare birds from the birding community each year. Th goals of each committee are to assess the identifiation, origin, date, and location of the rare birds reported, as well as to maintain the checklist for each state. In addition, each committee communicates records of rare bird sightings to the public through publications in journals and through the committee’s website. Th wealth of information found on each website can be used by researchers and birders alike. Ths review focuses on the websites of the eleven bird records committees in the western states and provinces and discusses how each website allows observers to submit documentation of rare birds and how effctively it conveys these records.

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    STEVE HAMPTON (Author)

    THE 2018 FLIGHT OF THE BUFF-BREASTED SANDPIPER

     For the Buffbreasted Sandpiper (Calidris subrufiollis), fall migration along the west coast of North America in 2018 was exceptional, with 70 individuals reported, fie to ten times the norm. Th one at Morro Strand State Beach, San Luis Obispo County, California, shown on this issue’s back cover, was representative.

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    THANK YOU TO OUR SUPPORTERS

     Th board of Western Field Ornithologists and the editorial team ofWestern Birds thank the following contributors for their fiancial support in 2019. Th growth of our youth scholarship program and of our publications have been possible only because of the remarkable generosity of our members.