Western Birds, the quarterly journal of Western Field Ornithologists, solicits papers that contribute significantly to the scientific literature and are useful and accessible to both professional and amateur field ornithologists. The journal welcomes contributions from professional and amateur scientists alike. Appropriate topics include distribution, migration, status, identification, geographic variation, conservation, behavior, ecology, population dynamics, habitat requirements, the effects of pollution, and techniques for censusing, sound recording, and photographing birds in the field. Papers of general interest will be considered regardless of their geographic origin, but particularly desired are reports of studies done in or bearing on the Rocky Mountain and Pacific states and provinces, including Alaska and Hawaii, western Texas, northwestern Mexico, and the northeastern Pacific Ocean.
OUTSTANDING MIGRATION AND NESTING RECORDS OF SWAINSON’S HAWKS IN SOUTHERN SONORA, MEXICO
We report multiple sightings of Swainson’s Hawks (Buteo swainsoni) migrating through the Yaqui Valley of Sonora, Mexico, in fall from 2021 to 2023. The hawks occurred in flocks of up to 800, associating with Turkey Vultures (Cathartes aura), Crested Caracaras (Caracara cheriway), and other birds foraging in farmland being plowed and tilled before the sowing of wheat for the fall–winter cropping season. On the basis of seven nests from 2023 to 2025, we also report the first evidence of Swainson’s Hawk nesting in the region, representing a southward expansion of the known breeding range by >250 km into the coastal plain of northwestern Mexico.
Copyright (c) 2026 Western Birds https://creativecommons.org/licenses/by-nc-sa/4.0
LEAST BELL’S VIREO NESTS IN THE SIERRA SAN PEDRO MÁRTIR, BAJA CALIFORNIA
Surveys for the Least Bell’s Vireo (Vireo bellii pusillus) during 18 field trips to four localities near the west base of the Sierra San Pedro Mártir in Baja California, Mexico, yielded detection of 42 individual vireos and 41 nests, 15 in various stages of use and 26 old. Arroyo willow (Salix lasiolepis) was the plant most frequently found supporting these nests, and the big sagebrush (Artemisia tridentata) was second, even though it has not been reported previously as a site of Least Bell’s Vireo nests. Other plants newly identified as supporting nests of this vireo were the single-whorl burrobrush (Ambrosia monogyra), hoary coffeeberry (Frangula californica tomentella), and holly-leaf cherry (Prunus ilicifolia). Rancho Meling, where we found the most vireos, has long been known as a site for the species, but ranchos El Potrero and La Costilla represent newly identified sites. Only one of the 15 active nests had been parasitized by the Brown-headed Cowbird (Molothrus ater).
CHANGES IN BREEDING BIRD ABUNDANCE AFTER THE KINCADE FIRE, SONOMA COUNTY, CALIFORNIA
Birds’ responses to wildfire have been well studied in southern California and the Sierra Nevada, but less attention has been paid to central and northern coastal California, a region with frequent high-intensity fires. Using a combination of data from a structured point-count survey and incidental community-science data (eBird.org), we compare bird species’ abundance three years before and after the Kincade Fire, which burned 314.6 km2, including along Pine Flat Road in Sonoma County, California, in October 2019. The point-count protocol consisted of a 5-minute count at 16 points repeated three times per season in April and May for three years both before and after the fire (except for just a single survey in 2016). Of 42 species modeled, 10 decreased in abundance following the fire, most notably the Band-tailed Pigeon (Patagioenas fasciata; 99% by both methods). The Western Meadowlark (Sturnella neglecta) colonized, and two, the Red-winged Blackbird (Agelaius phoeniceus) and Steller’s Jay (Cyanocitta stelleri), increased according to both methods. As found in many studies of birds’ response to fire, the Lazuli Bunting (Passerina amoena) increased sharply, though this was attested by the point counts only. For two species, the Bushtit (Psaltriparus minimus) and California Thrasher (Toxostoma redivivum), the trend per eBird data was a decline whereas the trend per point-count data was an increase. Trends in the abundances of the remaining 27 species were only weakly related (21 species) or unrelated (5 species) to the fire.
PHENOLOGY OF THE FIRST REPORTED CASE OF SAME-SEASON NEST REUSE IN ANNA’S HUMMINGBIRD
Natural history observations of rare events can provide invaluable data about the range of variation in a trait or behavior. In birds, these fortuitous observations can help supplement scientific understanding of the timing and location of nesting behavior, events which are often difficult to observe. Reuse of cup nests is thought to be rare, but incidental reports document nest reuse both within and across breeding seasons. A chance instance of a female Anna’s Hummingbird (Calypte anna) initiating a nest on our balcony in California was an opportunity to make detailed observations of nesting phenology with photos and videos. After successful fledging of this first nest, the same female immediately initiated a second nesting attempt in the same nest. To our knowledge, this is the first documented case of a female Anna’s Hummingbird reusing a nest in the same season, and only the second case confirmed through direct observations in any hummingbird species.
OCCURRENCES OF THREE SPECIES OF GNATCATCHERS IN THE SAN GORGONIO PASS, CALIFORNIA
The San Gorgonio Pass is an important zone of interchange between desert and coastal flora and fauna in southern California. We report multiple recent observations of California Gnatcatchers (Polioptila californica) within the pass, apparently persisting since their first documentation in 1908. While the Blue-gray Gnatcatcher (P. caerulea) has been documented here for more than a century, the occurrence of the California Gnatcatcher in this area is not widely known and not included in recent distribution maps for this threatened species. We also report the expansion of the Black-tailed Gnatcatcher (P. melanura) into the pass in recent decades, forming one of the few zones of overlap between these two species. With its elevational gradients, vegetation mosaics, and shifting species ranges the San Gorgonio Pass serves as a potential refugium from various anthropogenic stressors including climate change. The pass is currently subject to piecemeal development and lacks any significant conservation areas. It deserves more comprehensive conservation planning attention.
THE 50TH ANNUAL REPORT OF THE CALIFORNIA BIRD RECORDS COMMITTEE: 2024 RECORDS
From its last report through 2024, the California Bird Records Committee reached decisions on 208 records involving 179 individuals of 70 species and one species pair, endorsing 178 records of 167 individuals. The first accepted records for California of the Stejneger’s Scoter (Melanitta stejnegeri), White-tailed Eagle (Haliaeetus albicilla), Blue Rock-thrush (Monticola solitarius), Song Thrush (Turdus philomelos), Siberian Pipit (Anthus japonicus), and Slate-throated Redstart (Myioborus miniatus) are outlined in this report. These additions bring the California list to 691 species. Other especially notable records detailed in this report include those of California’s second Xantus’s Hummingbird (Basilinna xantusii), second Jouanin’s Petrel (Bulweria fallax), second Oriental Greenfinch (Chloris sinica), second Tropical Parula (Setophaga pitiayumi), second and third Band-rumped Storm-Petrels (Hydrobates castro), third American Woodcock (Scolopax minor), and third and fourth Swallow-tailed Kites (Elanoides forficatus).
Index for Western Birds Volume 54.
Copyright (c) 2023 Western Birds https://creativecommons.org/licenses/by-nc-sa/4.0
IN MEMORIAM: THOMAS S. HEINDEL, 1936-2023
Thomas (Tom) Scott Heindel was born on 30 June 1936 in York, Pennsylvania, where he spent the early years of childhood.
FIRST REPORT OF INTENTIONAL SEED-EATING BY BLACK PHOEBES
The Black Phoebe (Sayornis nigricans) occurs year-round through most of its range in California and commonly breeds from March through June. Typically, it feeds almost exclusively on insects. While this may generally be true, I describe here repeated observations of Black Phoebes intentionally consuming seeds from a backyard bird feeder near Sacramento, California.
PREY SIZE DETERMINES HANDLING AND CAPTURE TACTICS IN THE WESTERN GREBE
To investigate the feeding behavior of the Western Grebe (Aechmophorous occidentalis), I observed the actions of one kept in a laboratory pool and fed fish of various sizes and in varying numbers during four trials per day. The grebe consumed fish under 4 cm in length underwater but brought all fish longer that 5 cm to the surface so they could be oriented for swallowing headfirst. The Western Grebe is likely gape-limited in its choice of fish and can only ingest prey that can be swallowed easily.
FIRST RECORD OF A SIBERIAN RUBYTHROAT (CALLIOPE CALLIOPE) IN THE CONTERMINOUS UNITED STATES
The first Siberian Rubythroat (Calliope calliope) recorded in the conterminous United States occurred in Santa Clara County, California, on 19 November 2022. The detection was made by a motion-activated trail camera, and the bird was not recorded thereafter.
RECENT INCREASE IN THE YELLOW-BILLED MAGPIE POPULATION IN SACRAMENTO AND ITS POSSIBLE CAUSES
The Yellow-billed Magpie (Pica nuttalli) declined substantially throughout its range after the West Nile virus arrived in California in the 2000s, and neither development of disease resistance nor population recovery have been reported. After surveying 8 occupied sites in 2020 and 22 occupied sites in 2021 for a study of the magpie’s habitat use in urban Sacramento, I continued surveying 15 urban parks in 2022 and 2023 to evaluate population trends over 4 years. The Sacramento magpie population increased consistently by 3–7% per year, suggesting a localized recovery. Since the extent of foraging habitat remained stable, other factors, possibly including development of resistance to the virus (as seen in other species of birds), may be promoting a population increase. These results, however, are local and relatively short term. More work is needed to determine if resistance is developing and to understand longer-term population and disease trends in other parts of the Yellow-billed Magpie’s range.
SEVENTH REPORT OF THE NEW MEXICO BIRD RECORDS COMMITTEE
During the period November 2010 through December 2022, the New Mexico Bird Records Committee reached final decisions on 1188 records involving 154 species plus three species groups, accepting 1051 records. Twenty species were added to the New Mexico state list, including one new to North America north of Mexico, the Rufous-necked Wood-Rail (Aramides axillaris), bringing the state list of species confirmed by specimen, photograph, or audio recording to 552 through 31 December 2022.
SITE USE AND SITE FIDELITY OF POST-BREEDING SWAINSON’S THRUSHES IN SOUTHERN OREGON
Because the relative threats to survival during each stage of the life cycle remain uncertain, understanding all aspects of the full annual cycle has become a priority for bird conservation. The time between the end of breeding and the onset of fall migration is poorly known in most neotropical migrants and may be fraught with peril as birds move away from accustomed breeding areas to find food sufficient to prepare for migration. Therefore, we explored the use by post-breeding adult Swainson’s Thrushes (Catharus ustulatus) of two bird-banding stations in southwestern Oregon over a combined total of 31 years. Though the stations are within the species’ breeding range it nests at neither. Of 547 nonbreeding adults captured, 15.5% (85) were molting flight feathers during at least one capture. On average, these molters arrived and left earlier (2 August–29 September) and stayed longer (18.5 days) than nonmolters (30 August–21 October; 7 days). Molters’ probability of being recaptured at the same site in subsequent years was higher. The estimated fidelity of molters was 0.35; that of nonmolters was 0.15. We infer that both categories represent short-distance movements of birds nesting nearby.
THE OREGON DARK-EYED JUNCO SHOULD BE CALLED JUNCO HYEMALIS OREGANA
John Kirk Townsend introduced the Oregon Junco to science as Fringilla oregana, but since 1856 it has been classified in the genus Junco as Junco oreganus, Junco oregonus, Junco hyemalis oreganus, or Junco hyemalis oregonus. The change of spelling to oregonus is not justified under the current International Code of Zoological Nomenclature, and since 1901 oreganus has been used universally. Under the code’s articles 31 and 34 adjectival species-group names (both species and subspecies) must agree in grammatical gender with the genus with which they are combined. Under Article 30, Junco is masculine, whereas Fringilla is feminine. If oregana is an adjective, as it has generally been construed, it needed to be changed to oreganus to agree with Junco. But the termination “-a” is ambiguous, and in ambiguous cases the code prescribes that the word be construed as a noun in apposition that remains unchanged regardless of the gender of the genus in which the species or subspecies is classified. This case parallels other similar examples that have been treated inconsistently in recent literature. A comprehensive review of such cases at the level of both species and subspecies is needed.
THE BIRDS OF GAMBELL AND ST. LAWRENCE ISLAND, ALASKA: NEW RECORDS AND OTHER UPDATES, 2019–2025
Much noteworthy avian information has accrued since the publication of The Birds of Gambell and St. Lawrence Island, Alaska (Lehman 2019). These include first-time records as well as many new early arrival and late departure dates, high counts, and additional records of rare and casual species. From 2019 to 2025, 14 new species were recorded on St. Lawrence Island. Two, Pallas’s Grasshopper Warbler (Helopsaltes certhiola) and the Icterine Warbler (Hippolais icterina), were also firsts for North America. Another two species were new at the village of Gambell but had previously been recorded elsewhere on the island. In addition, the taxonomic splits of the Vega Gull (Larus vegae) and American Herring Gull (L. smithsonianus) from the Herring Gull (L. argentatus) and of the Siberian Pipit (Anthus japonicus) from the American Pipit (A. rubescens) were accompanied by the merging of Common Redpoll (Acanthis flammea) and Hoary Redpoll (A. hornemanni) into a single species. These discoveries and reclassifications bring the species total at Gambell to 303 and on St. Lawrence Island to 307.
VARIABILITY IN COMMON CALL NOTES OF THE WINTER AND PACIFIC WRENS
We analyzed 175 calls of 91 individual Winter (Troglodytes hiemalis) and Pacific (Troglodytes pacificus) wrens by measuring characteristics such as peak frequency, frequency range, and complexity. We found considerable overlap in most measurements, but metrics such as peak frequency and trace shape are useful for distinguishing the two species. With these results, we recommend a standard for acceptance of extralimital Winter and Pacific wrens through evaluation of spectrograms quantifying the call’s peak frequency (higher in the Pacific, lower in the Winter), the shape and symmetry of the trace at the lowest frequency (more symmetrical in the Winter), and whether the lowest-frequency trace is tightly coupled with a second trace (favoring the Pacific).
AN ANALYSIS OF PLUMAGE CHARACTERISTICS OF THE WINTER AND PACIFIC WRENS
The Winter Wren (Troglodytes hiemalis Vieillot, 1819) and Pacific Wren (T. pacificus Baird, 1864) are closely related species occurring primarily in eastern and western North America, respectively. Recent literature on the identification of these cryptic species has focused on vocal cues, but subtle differences in plumage have also been proposed since Spencer F. Baird’s original description of the Pacific Wren in 1864. The nature and consistency of these differences need quantification for plumage to be useful in identification. We analyzed 11 prospective characters, finding strong differentiation in 6: Winter Wrens show stronger pale markings on the chest, neck, mantle, and alula, and feature a paler throat and supercilium, on average, than Pacific Wrens. Two variables, relative width of pale and dark bars on the primaries and number of pale tips on the upperwing coverts, are moderately informative, whereas we found three variables—relative tone of pale barring on primaries and on secondaries, relative throat color, and crown color—to show no consistent differences. Although differences in plumage between Winter and Pacific wrens are subtle, consideration of the six informative characters should be of material use in identifying many individuals to species.
Compiled by Philip Unitt
FEATURED PHOTO: A VAGRANT BELL'S SPARROW IN BAJA CALIFORNIA SUR
Although at least seven Sage Sparrow subspecies have been described, the species has generally been regarded as comprising five distinct subspecies (AOU 1957). Nominate belli is resident in chaparral from the inner northern Coast Ranges of California south to the coast in Marin County, and south along the coast and foothills through northern Baja California, west of the Sierra Juárez and Sierra San Pedro Mártir, to Santa Catarina Landing at 29°30′ N. Isolated populations occur in the western Sierra Nevada from El Dorado County south to Mariposa County (Grinnell and Miller 1944).
This addition to the growing series of identification guides to bird families treats only the 18 species of pipits and 9 of wagtails recognized by the authors as occurring in the Holarctic biogeographic region (ostensibly Eurasia and North America). The title is thus misleading, in that the book does not treat about half of the world's species of the Motacillidae. This approach, however, has advantages over the more common one of including all of the world's species in a given family, despite an author's lack of familiarity with many species. And the authors of Pipits and Wagtails have spent many years studying this group of birds, rather than deciding one day that they would simply like to write a book. As a consequence, Pipits and Wagtails stands virtually alone in this recent series: it is authoritative, well written, and full of literature citations. It should be a model for any future works in this genre.
BOOK REVIEWS: Raptors of Western North America,
Even in the brave new world of in-depth family monographs, Brian Wheeler's two volumes tread where few have wandered before. North America has long lacked a guide comparable to Dick Forsman's brilliant The Raptors of Europe and the Middle East, and Wheeler is the first to attempt to remedy this situation. The result is monumental, staggering in its scope, and, quite frankly, a mixed bag. If nothing else, these books break new ground in the world of raptor identification: there are a lot of ideas that go beyond what has been suggested before, many of which need to be tested in the field—some that may become standard in the future, others that will fall by the wayside. In two books with such detail, there is a tremendous amount of material to review. And while there are many errors, omissions, or nit-picky details to quibble over, it must be said that this is a highly commendable, deeply personal, and intensely scholarly effort on Wheeler's part. All North American birders and raptor specialists have much to learn from these books.
PURPLE MARTIN POPULATION STATUS, NESTING HABITAT CHARACTERISTICS, AND MANAGEMENT IN SACRAMENTO, CALIFORNIA
The Purple Martin (Progne subis) has been eliminated from most of California’s Central Valley. The last known population nests in elevated roadways (“bridges”) in the city of Sacramento. We reviewed bird records (1949–1990), conducted surveys to assess population size and trend (1991–2002), and evaluated management actions to protect and increase populations. Martins ceased nesting in buildings in Sacramento in the 1960s and 1970s as the European Starling (Sturnus vulgaris) population expanded, but adoption of vertical weep holes for nesting beneath bridges in the 1960s has allowed martins to persist. The known Sacramento population increased from four to seven colonies and from approximately 105 to 135 nesting pairs from 1992 to 2002. Martin colonies are located in longer (>85 m) bridge sections that provide at least 6 m of unobstructed airspace beneath the colonies. Management has included a pilot project to insert wire “nest guards” in weep holes to increase survival of young and protection of nesting colonies during construction activities near nests. Initial results indicate that nest guards reduce mortality of young falling from nests and do not result in increased competition for nest sites by starlings and other species. Exclusion of martins from nesting at a large colony to prevent disturbance from a construction project reduced nesting use of the site; such exclusion is not considered necessary to protect nesting birds. Martin recovery may require substantial management, including protecting and enhancing existing colonies, encouraging colonization of other elevated road sites, establishing martin use of artificial nest structures in unoccupied regions, and enlisting public adoption of management responsibility.
DECLINES IN THE BREEDING POPULATION OF VAUX'S SWIFTS IN NORTHEASTERN OREGON
I investigated trends in the breeding population of Vaux’s Swift (Chaetura vauxi) in northeastern Oregon by revisiting in 2003 39 stands of trees that contained swifts in 1991. In 2003, the number of swifts in these stands was significantly fewer, with only 46% of the stands still containing swifts. Only 29% of the 58 nest and roost trees the swifts were using from 1989 to 1997 were still suitable for nesting in 2003; the remainder had fallen over, broken off, or become filled with cavities. Factors that may be affecting the population include tree mortality caused by insect outbreaks and disease, tree harvesting, wildfire, climatic shifts, and habitat changes in the winter range.
CHARACTERISTICS OF TREES USED BY NESTING AND ROOSTING VAUX'S SWIFTS IN NORTHWESTERN CALIFORNIA
Given the limited information available on trees used by Vaux’s Swifts (Chaetura vauxi) in the coast redwood (Sequoia sempervirens) zone of California, we gathered information regarding site, tree, and nest characteristics of nest and roost trees found opportunistically by various observers. All 14 nest trees and four roost trees were redwoods. Twelve of the nests were found in basal hollows in large live trees (mean diameter at breast height [dbh] 306 cm); one was in a cavity formed at the base of two small live trees (dbh about 50 cm) that had grown together, and one was in a stump (height 1.3 m, dbh 128 cm). Three of the four roost trees were dead with broken tops; their mean height and dbh were 20.0 m and 229 cm, respectively. The fourth was a live tree 33.9 m in height and 297 cm in dbh. These trees were in areas experiencing varying levels of human activity. All nests were located well away from cavity entrances. Our findings suggest that fire plays an important role in the creation of suitable nest and roost trees and that the swifts’ tradition of using specific suitable trees lasts for many years.
MOLT, PLUMAGE, BODY MASS, AND MORPHOMETRICS OF A POPULATION OF THE WHITE-THROATED SWIFT IN SOUTHERN CALIFORNIA
Over a 10-year period, I examined molt patterns, plumage, and body-mass changes in a population of White-throated Swifts in the Mecca Hills, Riverside County, California, by sampling birds at regular roosts each month from February through November. The swifts used the roosts year-round, but numbers declined in March, then increased in June and July after breeding. As a result of plumage wear, the juvenal plumage can be categorized into three “phases”: prior to fledging, after fledging, and prior to the first prebasic molt. I found no sexual dimorphism in wingspan, wing length, tarsus length, tail length, culmen length, or body mass. I found an average difference between the sexes in the depth of the tail fork, but because of much overlap, it cannot be used to determine the sex of individuals. The maximum difference between highest and lowest body mass was 28.7%, less than reported for other species. Testis size began to increase in March, reaching a peak in April. Primary molt lasted 6–7 months, from May through November. Tail molt lasted about 2.5–3 months, from June through August. Breeding began at this desert site one to two months earlier than at a coastal site. The overlap of breeding and molt in this desert population appears to be less than reported for other species of swifts.
DIET OF BREEDING WHITE-THROATED AND BLACK SWIFTS IN SOUTHERN CALIFORNIA
We analyzed the diet of nestling White-throated (Aeronautes saxatalis) and Black Swifts (Cypseloides niger) in southern California. White-throated Swifts fed their nestlings boluses of insects that were more taxonomically diverse, on average (over 50 arthropod families represented), than those fed by Black Swifts (seven arthropod families, primarily ants). In some cases, White-throated Swift boluses contained primarily one species, while other boluses showed more variation. In contrast, all Black Swift samples contained high numbers of winged ants with few individuals of other taxa. Our results provide new information on the White-throated Swift’s diet and support previous studies of the Black Swift.
SOCIAL BEHAVIOR OF WHITE-THROATED SWIFTS
The social behavior of the White-throated Swift includes Chases Without Contact, Chases With Contact, and Courtship Falls. These behaviors show a strong seasonal pattern. Chases Without Contact were the most common interaction and occurred most frequently during the winter and spring. Chases With Contact and Courtship Falls occurred less frequently and peaked during spring prior to breeding. White-throated Swifts also exhibit social behaviors that may be termed the Raised-Wing display, Screaming Party, and Silent Dread.
SEASONAL POPULATION FLUCTUATION OF WHITE-THROATED SWIFTS AT ROOST SITES IN SOUTHERN CALIFORNIA
In southern California, White-throated Swift (Aeronautes saxatalis) roosts contain many more individuals during the winter months than during the breeding season. Dates of the high and low counts at these roosts fluctuate from site to site and from year to year. Evidence suggests that some individuals remain and nest at or near the roost; whether others migrate north to breeding areas remains unknown.
IN MEMORIAM: ALAN MACKENZIE CRAIG, 1935–2025 FOUNDING, SAVING, AND NURTURING WFO
I first recall meeting Alan Craig on 30 September 1967 in San Diego. I was 13.