Recent observations on the birds of the Koolau Forest Reserve, Maui
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Western Birds↗
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Utilizing artificial nesting platforms as a management tool: Enhancing breeding productivity of Western Flycatchers (Empidonax difficilis occidentalis) in southwestern Colorado and southern Arizona, USA
Artificial nesting substrates have been added around the world for many cavity-nesting bird species, but this has not been undertaken as extensively for crevice-nesting birds. The Western Cordilleran Flycatcher ( Empidonax difficilis occidentalis ) is a migratory, crevice-nesting flycatcher that is nest-site limited, breeding in higher elevation riparian habitats throughout intermountain western North America. We tested the effectiveness of multiple artificial nesting platform types that this flycatcher would accept for nesting, and then utilizing the successful design established an experimental array of platforms in southwestern Colorado and southern Arizona. From 2008 to 2022 we documented Cordilleran Flycatcher breeding and the influence of nesting platforms on productivity of young and adult numbers. Breeding behaviors did not differ significantly between natural nest sites and platform nests, except that the nestling period was an average of 16.73 (+/- 0.98) days on platforms as compared to 15.92 (+/- 0.71) on human structures and 15.67 (+/- 0.48) days in natural locations. Platform nests had lower predation rates and greater rates of successful fledging when compared to natural locations. At both study locations platform nests doubled the number of young fledged each year. In Colorado, where Western Cordilleran Flycatchers were initially absent from areas, adult numbers increased following introduction of platforms, but in Arizona adult flycatcher numbers were not affected. Our findings demonstrate that the addition of artificial nesting platforms can enhance productivity and numbers of Western Cordilleran Flycatchers, and we hope that our findings will prove useful for the conservation of other crevice-nesting bird species.
Arizona, Colorado↗
Introduction of Eurasian-origin H8N4 influenza A virus into North America via migratory birds
We identified a Eurasian-origin influenza A(H8N4) virus in North America by sampling wild birds in western Alaska, USA. Evidence for repeated introductions of influenza A viruses into North America by migratory birds suggests that intercontinental dispersal might not be exceedingly rare and that our understanding of viral establishment is incomplete.
Emerging Infectious Diseases↗
Spatial and temporal variation in climate change: A bird’s eye view
Recent changes in global climate have dramatically altered worldwide temperatures and the corresponding timing of seasonal climate conditions. Recognizing the degree to which species respond to changing climates is therefore an area of increasing conservation concern as species that are unable to respond face increased risk of extinction. Here we examine spatial and temporal heterogeneity in the rate of climate change across western North America and discuss the potential for conditions to arise that may limit the ability of western migratory birds to adapt to changing climates. Based on 52 years of climate data, we show that changes in temperature and precipitation differ significantly between spring migration habitats in the desert southwest and breeding habitats throughout western North America. Such differences may ultimately increase costs to individual birds and thereby threaten the long-term population viability of many species.
Climatic Change↗
Population genetics and evaluation of genetic evidence for subspecies in the Semipalmated Sandpiper (Calidris pusilla)
Semipalmated Sandpipers ( Calidris pusilla ) are among the most common North American shorebirds. Breeding in Arctic North America, this species displays regional differences in migratory pathways and possesses longitudinal bill length variation. Previous investigations suggested that genetic structure may occur within Semipalmated Sandpipers and that three subspecies corresponding to western, central, and eastern breeding groups exist. In this study, mitochondrial control region sequences and nuclear microsatellite loci were used to analyze DNA of birds (microsatellites: n = 120; mtDNA: n = 114) sampled from seven North American locations. Analyses designed to quantify genetic structure and diversity patterns, evaluate genetic evidence for population size changes, and determine if genetic data support the existence of Semipalmated Sandpiper subspecies were performed. Genetic structure based only on the mtDNA data was observed, whereas the microsatellite loci provided no evidence of genetic differentiation. Differentiation among locations and regions reflected allele frequency differences rather than separate phylogenetic groups, and similar levels of genetic diversity were noted. Combined, the two data sets provided no evidence to support the existence of subspecies and were not useful for determining migratory connectivity between breeding sites and wintering grounds. Birds from western and central groups displayed signatures of population expansions, whereas the eastern group was more consistent with a stable overall population. Results of this analysis suggest that the eastern group was the source of individuals that colonized the central and western regions currently utilized by Semipalmated Sandpipers.
Waterbirds↗
Use of a nesting platform by Gull-billed Terns and Black Skimmers at the Salton Sea, California
In 2006, we constructed an elevated nesting platform at the Salton Sea, California, and monitored its use by Gull-billed Terns and Black Skimmers over three subsequent breeding seasons. Black Skimmers were the first to colonize the platform with a total of five nests in 2006. In 2007 Gull-billed Terns colonized the platform with a total of 28 nests and the number of Black Skimmer nests increased to 20. Neither species nested on the platform in 2008. Low success for both species was probably influenced by at least two factors. First, when both species nested on the platform, nest densities were higher than is typical of their colonies on larger, earthen islands, and colony success may have been reduced by overcrowding. Second, lack of access to water may have reduced chicks' ability to thermoregulate effectively in the hot environment of the Salton Sea. Refinements to the size, design, and location of artificial nesting habitats are necessary to enhance productivity of colonial groundnesting birds at the Salton Sea successfully.
Western Birds↗
Dispersal of H9N2 influenza A viruses between East Asia and North America by wild birds
Samples were collected from wild birds in western Alaska to assess dispersal of influenza A viruses between East Asia and North America. Two isolates shared nearly identical nucleotide identity at eight genomic segments with H9N2 viruses isolated from China and South Korea providing evidence for intercontinental dispersal by migratory birds.
Virology↗
Reproductive biology of the band-tailed pigeon in Colorado and New Mexico
Band-tailed pigeons ( Columba fasciata ) occur in two major populations in western North America, a coastal population ( C. f. monilis ) and an interior population ( C. f. fasciata ) (A.O.U. 1957). The interior population inhabits portions of Colorado, New Mexico, Arizona, Utah, Texas, and the highlands of Mexico. This pigeon is one of several species of birds in western North America that show unseasonal and variable nesting periods (see Ligon 1971). Active nests have been found in some portion of the species' range in every month of the year (Swarth 1900, Thayer 1909, Stephens 1913, Lamb 1926, Abbott 1927, Vorhies 1928, Neff 1947, MacGregor and Smith 1955). Although several studies of the breeding biology of the Band-tailed Pigeon have been made on the Pacific coast population (Glover 1953, MacGregor and Smith 1955, Houston 1963, March and Sadleir 1970, Zeigler 1971) few studies have been done of the interior population (Fitzhugh 1970). The breeding cycle of the interior population is poorly understood, although many observations of individual nests have been reported (Neff 1947, Fitzhugh 1970). The purpose of this study was to document the gonadal cycles of free-living Band-tailed Pigeons in Colorado and New Mexico and to study the species' photoperiod responses. From this information we have attempted to explain the normal breeding cycle of the pigeon and to explain its occasional unseasonal breeding.
The Auk↗
Evidence that life history characteristics of wild birds influence infection rates and exposure to influenza A viruses
We report on life history characteristics, temporal, and age-related effects influencing the frequency of occurrence of avian influenza (AI) viruses in four species of migratory geese breeding on the Yukon-Kuskokwim Delta, Alaska. Emperor geese ( Chen canagica ), cackling geese ( Branta hutchinsii ), greater white-fronted geese ( Anser albifrons ), and black brant ( Branta bernicla ), were all tested for active infection of AI viruses upon arrival in early May, during nesting in June, and while molting in July and August, 2006–2010 ( n = 14,323). Additionally, prior exposure to AI viruses was assessed via prevalence of antibodies from sera samples collected during late summer in 2009 and 2010. Results suggest that geese are uncommonly infected by low pathogenic AI viruses while in Alaska. The percent of birds actively shedding AI viruses varied annually, and was highest in 2006 and 2010 (1–3%) and lowest in 2007, 2008, and 2009 (<0.70%). Contrary to findings in ducks, the highest incidence of infected birds was in late spring when birds first arrived from staging and wintering areas. Despite low prevalence, most geese were previously exposed to AI viruses, as indicated by high levels of seroprevalence during late summer (47%–96% across species; n = 541 ). Seroprevalence was >95% for emperor geese, a species that spends part of its life cycle in Asia and is endemic to Alaska and the Bering Sea region, compared to 40–60% for the other three species, whose entire life cycles are within the western hemisphere. Birds <45 days of age showed little past exposure to AI viruses, although antibodies were detected in samples from 5-week old birds in 2009. Seroprevalence of known age black brant revealed that no birds <4 years old had seroconverted, compared to 49% of birds ≥4 years of age.
Alaska↗
Additions to the avifauna of St Matthew Island, Bering Sea
St. Matthew Island (60°24' N, 172 ° 42' W) is located in the north-central Bering Sea and is renowned for its distinctive Beringian flora and fauna. Because of its central position between the coasts of Russia and Alaska, St. Matthew Island and its nearby satellites, Hall and Pinnacle islands, support a mixture of Palearctic and Nearctic avifaunas. Of special interest to North American ornithologists are the numerous Eurasian bird species that visit the islands each spring and fall. Winker et al. (2002) published the first comprehensive summary of bird records for the 125 species detected on St. Matthew Island from 1899 to 1997. Because of its remote location, however, St. Matthew Island is seldom visited, and the island's avifauna remains poorly described. As part of an island-wide systematic survey for Rock Sandpipers ( Calidris ptilocnemis ) and McKay's Buntings ( Plectrophenax hyperboreus ), our crew of five ornithologists was present on St. Matthew Island from 25 May to 9 July 2003. In this paper we provide information for 11 bird species seen for the first time on St. Matthew Island. Phylogenetic sequence and nomenclature follow the American Ornithologists' Union (1998, 2000) and Banks et al. (2002, 2003, 2004). An annotated species list with details of observation is on file at the University of Alaska Museum, Fairbank.
Alaska↗
Further information on the avifauna of St. Matthew and Hall Islands, Bering Sea, Alaska
In June and July 2018 and July 2019 we surveyed birds on St. Matthew and Hall islands, isolated in the central Bering Sea. Our surveys were focused on the McKay’s Bunting (Plectrophenax hyperboreus), Rock Sandpiper (Calidris ptilocnemis ptilocnemis), and Pelagic Cormorant (Phalacrocorax pelagicus) but encompassed all birds and yielded 13 species and four subspecies new to the islands’ avifaunal list, and new details and documentation of breeding for eight species. Especially notable discoveries include a mixed pair of Bewick’s (Cygnus columbianus bewickii) and Whistling (C. c. columbianus) Swans, a mixed pair of the Glaucous-winged (Larus glaucescens) and an Asian subspecies of the Herring Gull (L. argentatus vegae), and discovery of a colony of ~100 pairs of the Red-legged Kittiwake (Rissa brevirostris). Also, contrary to many previous expeditions, we found the Gray-crowned Rosy-Finch (Leucosticte tephrocotis umbrina) to be common and conclude that it may be resident.
Alaska↗
Severe bill deformity of an American Kestrel wintering in California
During a recent survey for West Nile virus in wild birds around the Sonny Bono Salton Sea National Wildlife Refuge, Imperial County, California (Dusek et al. 2010), we captured a female American Kestrel ( Falco sparverius ) with a severe bill deformity (Figure 1). The kestrel was captured on 9 March 2006, at 08:45, approximately 0.25 km south of the intersection of Wiest and Lindsey roads (33° 08' 42' N, 115° 26' 59' W) and 6 km east-northeast of Calipatria. It was caught on a bal-chatri trap baited with a domestic mouse (Berger and Mueller 1959), as were all the 208 kestrels captured during this study. The bird was initially perched on a high transmission line running along Wiest Road and was caught within 10 minutes of our setting the trap. In examining the bird, we observed that the maxilla beyond the cere was missing. The upper bill structure from the palatine process, which included part of the maxilla, the entire premaxilla, and the external rhamphotheca (the hardened keratin layer cover ing the premaxilla) was missing rostral to the bird's cere and nares (Threlfall 1968, Lucas and Stettenheim 1972, Proctor and Lynch 1993). The epidermal layer of the cere appeared to have fused over the remaining area between the nares where the upper bill normally would have been. The deformation did not appear to be recent or related to our trapping, as there were no obvious abrasions or open wounds in the region surrounding the nares and oropharynx or signs of recent trauma surrounding the oropharynx area. Both nares were clearly defined, and the tongue protruded from the open oropharynx area. After completing the physical examination, measurements, and obtaining a blood sample for testing for West Nile virus, we released the kestrel at the location of capture. After its release, we monitored the kestrel's behavior for approximately 30 minutes but did not observe any additional hunting.
California↗
Winter habitat associations of diurnal raptors in Californias 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, Redtailed 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.
Western Birds↗
Identification of CD3+ T lymphocytes in the green turtle Chelonia mydas
To understand the role of the immune system with respect to disease in reptiles, there is the need to develop tools to assess the host's immune response. An important tool is the development of molecular markers to identify immune cells, and these are limited for reptiles. We developed a technique for the cryopreservation of peripheral blood mononuclear cells and showed that a commercially available anti-CD3 epsilon chain antibody detects a subpopulation of CD3 positive peripheral blood lymphocytes in the marine turtle Chelonia mydas . In the thymus and in skin inoculated with phytohemagglutinin, the same antibody showed the classical staining pattern observed in mammals and birds. For Western blot, the anti-CD3 antibodies identified a 17.6 kDa band in membrane proteins of peripheral blood mononuclear cell compatible in weight to previously described CD3 molecules. This is the first demostration of CD3+ cells in reptiles using specific antibodies.
Quintana Roo↗
Timing of autumn bird migration under climate change: advances in long–distance migrants, delays in short–distance migrants
As a response to increasing spring temperature in temperate regions in recent years, populations of many plant and animal species, including migratory birds, have advanced the seasonal start of their reproduction or growth. However, the effects of climate changes on subsequent events of the annual cycle remain poorly understood. We investigated long–term changes in the timing of autumn migration in birds, a key event in the annual cycle limiting the reproductive period. Using data spanning a 42–year period, we analysed long–term changes in the passage of 65 species of migratory birds through Western Europe. The autumn passage of migrants wintering south of the Sahara has advanced in recent years, presumably as a result of selection pressure to cross the Sahel before its seasonal dry period. In contrast, migrants wintering north of the Sahara have delayed autumn passage. In addition, species with a variable rather than a fixed number of broods per year have delayed passage, possibly because they are free to attempt more broods. Recent climate changes seem to have a simple unidirectional effect on the seasonal onset of reproduction, but complex and opposing effects on the timing of subsequent events in the annual cycle, depending on the ecology and life history of a species. This complicates predictions of overall effects of global warming on avian communities.
Proceedings of the Royal Society B: Biological Sci↗
Changes in the abundance and distribution of waterfowl wintering in the Central Valley of California, 1973–2000
The Central Valley of California is one of the most important areas for wintering waterfowl in the world and the focus of extensive conservation efforts to mitigate for historical losses and counter continuing stressors to habitats. To guide conservation, we analyzed trends in the abundance and distribution (spatiotemporal abundance patterns) of waterfowl and their habitats in the Central Valley and its major subregions (Sacramento Valley, Suisun Marsh, Delta, San Joaquin Valley), from 1973 through 2000. We used existing databases, satellite imagery, and aerial photography to measure habitat area, and aerial surveys and radio telemetry to track the abundance and distribution of wintering waterfowl. Wetlands increased throughout the Central Valley, but agricultural fields flooded after harvest increased greatly to the north in the Sacramento Valley and decreased to the south in the San Joaquin Valley, resulting in an overall increase in the relative availability of winter habitat in the former region. Reflecting the continental decline of the most abundant wintering species (Northern Pintail, Anas acuta ), the overall abundance of wintering waterfowl in the Central Valley declined during our study. By contrast, numbers of the American Wigeon ( A. americana ), Mallard ( A. platyrhynchos ), and Northern Shoveler ( A. clypeata ) were stable, and numbers of the Green-winged Teal ( A. crecca ), Gadwall ( A. strepera ), diving ducks, and geese increased from 1973–1982 to 1998–2000. The areas of greatest abundance of wintering waterfowl within the Central Valley shifted northward as many species responded to changes in the distribution of habitats. Wintering waterfowl migrated earlier in fall and winter from the San Joaquin Valley, Suisun Marsh, and Delta to the Sacramento Valley, and fewer waterfowl emigrated from the Sacramento Valley to other parts of the Central Valley. Because changes in waterfowl distribution were primarily a response to the increase of a beneficial agricultural practice (i.e., the flooding of rice after harvest) in the Sacramento Valley, changing agro-economics, reduction of water supplies, or other factors that reduce this practice could change the abundance and distribution of wintering waterfowl in the Central Valley rapidly. Thus to maintain abundant suitable habitat and restore the historical distribution of wintering waterfowl, our results suggest a continuing need for the conservation of wetlands and other waterfowl habitats with secure water supplies throughout the Central Valley. Despite our findings, achieving goals for winter waterfowl populations in the Central Valley likely will depend on a combination of factors including some acting in breeding ranges farther north or elsewhere outside of the valley.
California↗
Flammulated Owls (Otus flammeolus) on Santa Barbara Island: First Records for the California Channel Islands
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Western Birds↗