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 Hawai'i, western Texas, northwestern Mexico, and the northeastern Pacific Ocean.
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.
International Code of Zoological Nomenclature birds
geographic epithets zoological nomenclature
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.
Book Review: Birds of the Pacific States
If you ask almost any birder to name the person who created the first modern field guide to North American birds, one designed to help identify birds in the field, pointing out a few key field marks for each along with descriptions of their sounds—you will be confidently assured that Roger Tory Peterson was that person. It turns out that “almost any birder” would be dead wrong.
FIRST NORTH AMERICAN RECORD OF THE ORIENTAL HONEY-BUZZARD (PERNIS PTILORHYNCHUS)
On 27 May 2024, Pohlen and Benter observed an adult female Oriental Honey-buzzard (Pernis ptilorhynchus) at Eareckson Air Station, Shemya Island, Aleutian Islands, Alaska—a first record for North America. The presence of six prominent primaries, cinnamon underside, and absence of dark carpal patches are diagnostic of this species and exclude the European Honey-buzzard (P. apivorus), a similar-looking congener unknown in North America.
ACTIVITY PATTERNS OF WHITE-THROATED SWIFTS IN CALIFORNIA
We investigated the daily and seasonal activity patterns of the White-throated Swift and related these patterns to seasonal changes in day length and variation in environmental conditions. The time of morning exit from the roost fluctuated more with daily variation in the weather than by season, occurring later after sunrise when temperatures were cool, particularly during winter. Exit time was also delayed if temperatures rapidly exceeded the optimal range for aerial insect activity shortly after sunrise. Exits were further delayed by rain. The evening return of White-throated Swifts to their roost fluctuated more predictably with season, although entry times were also influenced by weather. Entry time was delayed when temperatures were cold and occurred earlier when they were warm or hot, or during rain. The pattern of group entry varied by season. In winter, evening roost entry was clumped, with large numbers of swifts entering together. In spring, entry was more scattered, with smaller groups entering over a longer period. The pattern of morning exit was clumped year-round, with most swifts exiting together as a group.
SECOND RECORD OF THE TROPICAL PARULA IN CALIFORNIA AND THE SPECIES’ STATUS IN THE WESTERN UNITED STATES
A Tropical Parula (Setophaga pitiayumi) photographed and audio-recorded in Big Dalton Canyon, Los Angeles County, 12–14 May 2024 established a second record of the species for California and the first in spring or summer. Another sighting at the Switzer Picnic Area, 30.5 km to west but also within the San Gabriel Mountains, 4 July–26 September 2024, likely represented the same individual. Only the two northernmost subspecies of the Tropical Parula are partially migratory, S. p. nigrilora, which nests in eastern Mexico and north into south Texas, and S. p. pulchra, which is found along the Sierra Madre Occidental. The broad white wingbars, deep orange flanks, and pattern of the song identify the bird in the San Gabriel Mountains as pulchra. Narrower wingbars, paler flanks, and pattern of the song identify California’s previous Tropical Parula, at Huntington Beach, Orange Co., 5 January–14 February 2018, as nigrilora. Despite its relatively sedentary nature, the Tropical Parula has been detected as a vagrant in Colorado, Kansas, northern Texas, New Mexico, Arizona, and now at least twice in California.
WING-STRIPE METRICS FOR IDENTIFYING SUBSPECIES OF THE ROCK SANDPIPER
Identification in formative and basic plumage of two of the three subspecies of the Rock Sandpiper breeding in Alaska—Calidris ptilocnemis tschuktschorum and C. p. couesi—remains problematic, although a difference in the white wing stripe has been reported qualitatively. For all three of Alaska’s breeding subspecies, including C. p. ptilocnemis, I used three criteria to quantify the wing stripe on each of the inner primaries and on the outer and middle secondaries of numerous specimens and birds photographed. The white stripe is significantly more extensive in tschuktschorum than in couesi, and even more extensive in ptilocnemis, but there is overlap, especially near the zones of contact between the subspecies. The combined criteria can support subspecific identification, of at least some Rock Sandpipers, even in the formative and basic plumages.
FEATURED PHOTO: DIET AND FEEDING ACTIVITY AT A FLAMMULATED OWL NEST IN IDAHO
The Flammulated Owl (Otus flammeolus) is a small, cavity-nesting species that feeds on a wide variety of nocturnal arthropods (Marshall 1957, Johnson and Russell 1962, Ross 1969). Various studies throughout western North America during the breeding season have found species in the order Lepidoptera (moths and their larvae) and/or Orthoptera (crickets and grasshoppers) to constitute the majority of this owl’s diet, with Coleoptera (beetles), Dermaptera (earwigs), Araneae (spiders), Chilopoda (centipedes), and miscellaneous insects making up a smaller percentage (Goggans 1986, Reynolds and Linkhart 1987, Powers et al. 1996).
CHIP CALLS IN THE WESTERN AND EASTERN WOOD-PEWEES
The chip call of the Eastern Wood-Pewee (Contopus virens) is a frequently cited feature of that species’ vocal repertoire, but similar calls of the Western Wood-Pewee (C. sordidulus) are usually overlooked. Differences in this call between the two species would aid in field identification of migrants, which rarely sing their diagnostic songs. Cross-correlations of audiospectrograms, comparisons of three audiospectrographic measures, and qualitative analysis of spectrograms show that most chip calls of the Eastern Wood-Pewee are not distinguishable from those of the Western Wood-Pewee, and Eastern chip calls are generally more variable than those of the Western. These analyses also show that the two wood-pewees are more similar to each other than they are to their respective sister taxa. This similarity raises questions about the role of chip calls in the behavior of Contopus species, especially as it relates to potentially shared functions and sources of selection in their nonbreeding ranges.
BOOK REVIEW: Birds of Oregon : A General Reference
This highly anticipated publication (hereafter BOGR) is not your usual state bird book for a couple of reasons. The first can be detected in the subtitle—it is more than just “status and distribution.” The second is indicated in the listing of three editors; not only were there an additional four principal contributors, but the actual species accounts were authored by about 100 volunteers recruited from among the state’s birders, biologists, and researchers. Given the total number of contributors, this book probably also stands out as being more eagerly awaited than any other state bird book.
A REVIEW OF LIFE-STAGE-SPECIFIC PREDATORS OF FOUR ENDEMIC HAWAIIAN WATERBIRDS
Hawaiian wetlands provide habitat for seven indigenous waterbirds. Of the six endemic to Hawai‘i, the U.S. Fish and Wildlife Service has designated five as endangered and one as threatened; maintaining their populations requires control of introduced species of predators. Their susceptibility to depredation varies by life stage, and they should be managed strategically to offset vulnerabilities specific to each life stage. A review of the literature for life-stage-specific predators of the eggs, chicks, and adults of the endemic Hawaiian Duck (Anas wyvilliana, koloa maoli), Hawaiian Coot (Fulica alai, ‘alae ke‘oke‘o), Hawaiian Gallinule (Gallinula galeata sandvicensis, ‘alae ‘ula), and Hawaiian Stilt (Himantopus mexicanus knudseni, ae‘o) yielded 99 sources and identified 17 predators, encompassing birds, mammals, reptiles, amphibians, and fish. Eleven species of predators took eggs or chicks; only four took adults. Although some predators may have been reported taking only one of the waterbirds, it is likely they pose at least some risk to all four taxa. However, variation in behavior and habitat among the four waterbirds may lead to slightly different predation pressures. Aquatic predators likely have a propensity for the more aquatic duck, coot, and gallinule chicks. Managers of Hawaiian waterbirds will require many tools and resources to combat predators that occupy land, air, and water, but control should focus on the most devastating taxa—nonnative birds and mammals.
Hawaiian Stilt (Himantopus mexicanus knudseni)
NESTING OF WESTERN GULLS IN BAHIA DE SANTA MARIA-LA REFORMA, SINALOA, MEXICO
The Western Gull breeds on islands along the Pacific coast of North America from southern Washington to southern Baja California but, before the observations we report here, had never been reported breeding in the Gulf of California (American Ornithologists’ Union 1998; Everett and Anderson 1994; Howell and Webb 1995; Pierotti and Annett 1995; Wilbur 1987). Non-breeding individuals, mostly immature, range into the Gulf of California as far north as Puerto Peñasco and as far south as Bahía Guásimas (Russell and Monson 1998). They are frequently found among Yellow-footed Gulls (Larus livens).
CHRISTMAS BIRD COUNT DATA CONFIRM NORTHWARD CONTRACTION OF THE NONBREEDING RANGE OF THE WHITE-WINGED SCOTER
Analysis of 50 years (1974/75–2023/24) of 123 Christmas Bird Counts along the east and west coasts of North America and in the Great Lakes region reveals a substantial decline of the White-winged Scoter (Melanitta deglandi) along the more southern segments of its winter range. All 16 of the California count circles examined showed a decline, which from Sonoma County south averaged 8.5% per year over the 50 years. The segment from Washington to northwestern California saw a smaller but still significant decline of 2.2% per year, while on counts in British Columbia and Alaska White-winged Scoter numbers increased slightly, at rate of 1.4% per year. On the east coast, from New Jersey south to Florida, White-winged Scoter numbers declined 5.8% per year, as well as in 18 of the 22 count circles in that segment. The northern and central segments of the east coast showed smaller but significant declines of 1.4 and 0.6% per year, respectively. The Great Lakes host fewer wintering White-winged Scoters than does either coast; Christmas Bird Count data from that region showed no clear trend. It is unclear whether our findings reflect a decline in the White-winged Scoter’s population rangewide, a northward shift in the coastal nonbreeding range into areas not well surveyed by Christmas Bird Counts, or combination of the two. The increase in sea-surface temperatures on both coasts of approximately 1o C since the 1970s may be a factor.
White-winged Scoter (Melanitta deglandi)
Christmas Bird Count (CBC) long-term trends
Waterfowl population decline North America
Climate change effects on seabirds (sea-surface temperature)
HISTORICAL AND CURRENT BREEDING STATUS OF THE PEREGRINE FALCON IN THE EASTERN SIERRA OF MONO AND INYO COUNTIES, CALIFORNIA
Historical data suggest that over 100 pairs of the Peregrine Falcon (Falco peregrinus) were nesting in California prior to the mid-1940s. Because of the deleterious effects of DDE, a sharp decline began in the 1950s, and by 1970 only about 5% of the population remained. Following pesticide restrictions and aggressive management and recovery efforts using captive-bred Peregrines, the population rebounded rapidly and continues to increase into the 21st century. Although information necessary to enable the species’ conservation was circulated, few details on its historical and recent breeding status at either the statewide or regional level have been published. Here we report available details for breeding Peregrines in the eastern Sierra Nevada of Mono and Inyo counties. Data on seven suspected historical breeding locations are sparse. Since 2005, breeding has been verified or suspected at 14 locations, 11 spanning the length of Mono County and 3 at dispersed locations in Inyo County. Of these, four were newly identified in 2025. Despite the dramatic comeback, vigilance and monitoring are needed. Notably, Peregrine mortality from highly pathogenic avian influenza may be an important cause of population decline in many regions of North America, including California, since 2022. Although the effects appear to have been greatest in coastal areas, where the falcons depend heavily on shorebirds and waterfowl (known to carry avian flu), problems have surfaced inland, including possibly at the base of the eastern Sierra where these prey concentrate in spring and summer at saline lakes and freshwater reservoirs.
Peregrine Falcon breeding ecology California
Falco peregrinus population recovery Sierra Nevada
Eastern Sierra Nevada raptor nesting distribution
Mono and Inyo counties bird conservation
Habitat use and nesting sites Peregrine Falcon
EXTENSION OF THE NORTHERNMOST BREEDING RANGE OF THE WHITE-COLLARED SWIFT IN WESTERN MEXICO
The White-collared Swift (Streptoprogne zonaris) ranges from Argentina and Bolivia in the south to the West Indies and Mexico in the north (Howell and Webb 1995, American Ornithologists’ Union 1998). Howell and Webb (1995) described the species as an uncommon nonbreeding transient, vagrant, or winter visitor in the west-central part of Mexico and suggested that birds from Jalisco and Colima might belong to the subspecies albicincta from southern Central America. Edwards (1972) reported the swift without details from Nayarit, and a few northerly vagrants have been reported in the United States (Hardy and Clench 1982, Lasley 1984, Erickson et al. 1989, American Ornithologists’ Union 1998). The northernmost breeding population in western Mexico is reported for the state of Guerrero (Rowley and Orr 1962, Howell and Webb 1995).