Birds In Alaska Research Articles

Latitudinal gradients and sex differences in morphology of the Black Oystercatcher (Haematopus bachmani).

Environment and behavior are widely understood to affect bird morphology, which can lead to differences among subspecies or populations within a wide-ranging species. Several patterns of latitudinal gradients in morphology have been described, though Allen's and Bergmann's rules are the most well-known and have been tested and confirmed across a diversity of taxa and species. These state that individuals at higher latitudes will have larger bodies (Bergmann's Rule) but smaller extremities (Allen's Rule) to conserve heat in colder climates. Migratory behavior also can influence avian morphology, particularly wing shape, where migratory birds tend to have longer, more pointed wings than residents. The Black Oystercatcher (Haematopus bachmani) is a large, partially migratory shorebird species restricted to intertidal habitats and distributed from Alaska to Baja California, spanning about 35° of latitude. A large proportion of Black Oystercatchers that breed in Alaska are migratory, where nearly all individuals breeding in British Columbia through the southern end of their range remain resident through the annual cycle. Their broad latitudinal range and diversity in migratory behavior may drive geographic variation in morphology. Here we evaluate three explanations for geographic variation in morphology of the Black Oystercatcher using data from seven sites across two regions: Alaska and British Columbia. We found evidence consistent with Allen's but not Bergmann's rule; birds in Alaska have shorter bills than those in British Columbia, and these findings held when controlling for body size using wing length. Despite regional differences in migratory behavior, we detected no difference in the wing shape of birds in Alaska and British Columbia. Differences between sexes and among sites suggest that multiple factors drive patterns of morphological variation in the Black Oystercatcher.

The importance of nighttime length to latitudinal variation in avian incubation attentiveness

Avian incubation provides an opportunity to test how parental behavior and ecological conditions interact to shape variation in offspring traits along geographic gradients. In particular, the duration of the incubation period is shorter at higher latitudes, but the degree to which this pattern arises from genetic divergence in rates of growth and development versus from parentally‐mediated variation in egg temperatures is controversial. At higher latitudes parents have higher daytime incubation attentiveness, i.e. they spend a greater proportion of the day on the nest. However, interpreting latitudinal variation in behavior is complicated by latitudinal patterns in ambient temperature and day length. Here, we use 24‐h video recordings to compare the incubation behavior of orange‐crowned warblers Leiothlypis celata in California and Alaska and test how attentiveness varies between populations and as a function of temperature. Birds in Alaska had higher nest attentiveness during the day, despite experiencing similar ambient temperatures. However, when analyzed over 24‐h, the longer nighttime period in California almost entirely canceled out daytime attentiveness differences between populations, and differences in 24‐h attentiveness were small. Our work highlights how incorporating nighttime incubation behavior qualitatively alters latitudinal patterns of attentiveness, and how lower ambient temperatures cannot account for the higher attentiveness in a high latitude population. These populations differ in their incubation period lengths, and differentiating between evolved versus environmentally‐induced variation in offspring growth and development will help understand the fitness consequences of variation in developmental periods.

Effects of climate change and environmental variability on the carrying capacity of Alaskan seabird populations

ABSTRACT Marine birds in Alaska, USA, have been monitored systematically for more than 4 decades, and yet it remains unclear why some populations have increased while others have declined. We analyzed the population dynamics of 5 seabird species—Black-legged (Rissa tridactyla) and Red-legged kittiwakes (R. brevirostris), Common (Uria aalge) and Thick-billed murres (U. lomvia), and Tufted Puffins (Fratercula cirrhata)—across 4 decades in Alaska. We tested hypotheses that each species' carrying capacity varied continuously through time with climate cycles and/or in response to habitat covariates. Using an information-theoretic approach, we evaluated competing candidate stochastic growth models of each species' annual rate of change, incorporating various environmental covariates. The North Pacific Index and Pacific Decadal Oscillation were the most important climatic covariates across the whole of Alaska, where the former generally was negatively related to rates of population change, and the latter positiv...

Striking difference in response to expanding brood parasites by birds in western and eastern Beringia

Two species of obligate brood-parasitic Cuculus cuckoos are expanding their ranges in Beringia. Both now breed on the Asian side, close to the Bering Strait, and are found in Alaska during the breeding season. From May to July 2017, we used painted 3D-printed model eggs of two cuckoo host-races breeding in northeastern Siberia to test behavioral responses of native songbirds on both sides of the Bering Strait, with particular attention to species that are known cuckoo hosts in their Siberian range. Each host nest was tested after the second egg was laid and, if possible, again 4 days later with a model of a different type. Although our Siberian study site was also outside the known breeding ranges of the cuckoos, we found that Siberian birds had strong anti-parasite responses, with 14 of 22 models rejected. In contrast, birds in Alaska had virtually no detectable anti-parasite behaviors, with only one of 96 models rejected; the rejecters were Red-throated Pipits (Anthus cervinus). Such differences suggest that the cuckoos might successfully parasitize naive hosts and become established in North America whether or not their historic host species are widely available. (Less)

Reassortment ofInfluenza A Virusesin Wild Birds in Alaskabefore H5 Clade 2.3.4.4 Outbreaks.

Sampling of mallards in Alaska during September 2014–April 2015 identified low pathogenic avian influenza A virus (subtypes H5N2 and H1N1) that shared ancestry with highly pathogenic reassortant H5N2 and H5N1 viruses. Molecular dating indicated reassortment soon after interhemispheric movement of H5N8 clade 2.3.4.4, suggesting genetic exchange in Alaska or surrounds before outbreaks.

Novel Picornavirus Associated with Avian Keratin Disorder in Alaskan Birds.

ABSTRACTAvian keratin disorder (AKD), characterized by debilitating overgrowth of the avian beak, was first documented in black-capped chickadees (Poecile atricapillus) in Alaska. Subsequently, similar deformities have appeared in numerous species across continents. Despite the widespread distribution of this emerging pathology, the cause of AKD remains elusive. As a result, it is unknown whether suspected cases of AKD in the afflicted species are causally linked, and the impacts of this pathology at the population and community levels are difficult to evaluate. We applied unbiased, metagenomic next-generation sequencing to search for candidate pathogens in birds affected with AKD. We identified and sequenced the complete coding region of a novel picornavirus, which we are calling poecivirus. Subsequent screening of 19 AKD-affected black-capped chickadees and 9 control individuals for the presence of poecivirus revealed that 19/19 (100%) AKD-affected individuals were positive, while only 2/9 (22%) control individuals were infected with poecivirus. Two northwestern crows (Corvus caurinus) and two red-breasted nuthatches (Sitta canadensis) with AKD-consistent pathology also tested positive for poecivirus. We suggest that poecivirus is a candidate etiological agent of AKD.

Elements in Whole Blood of Northwestern Crows (Corvus caurinus) in Alaska, USA: No Evidence for an Association with Beak Deformities

A recent outbreak of beak deformities among resident birds in Alaska, US, has raised concern about environmental contamination as a possible underlying factor. We measured whole blood concentrations of 30 essential and nonessential elements to determine whether any were associated with beak deformities in Northwestern Crows ( Corvus caurinus ). We tested for differences between 1) adults with versus those without beak deformities and 2) unaffected adults versus juveniles. Crows with beak deformities had slightly higher levels of barium, molybdenum, and vanadium (all P<0.05), but concentrations were generally low and within the range of values reported from other apparently healthy wild birds. Concentrations of several elements, including selenium, were higher in birds without versus birds with beak deformities (all P<0.05), a difference that may be explained in part by compromised foraging ability associated with the deformities. Adult crows had higher concentrations of cadmium, silicon, and zinc than juveniles (all P<0.05), although differences were relatively small and values were similar to those from other wild birds. Our results suggest that neither selenium nor other tested elements are likely to be causing beak deformities in Alaskan crows. We also provide the first data on elemental concentrations in Northwestern Crows. Levels of selenium far exceeded those typically found in passerine birds and were similar to those in marine-associated waterfowl, suggesting that background levels should be interpreted relative to a species' environment.

Evidence for intercontinental parasite exchange through molecular detection and characterization of haematozoa in northern pintails (Anas acuta) sampled throughout the North Pacific Basin.

Empirical evidence supports wild birds as playing a role in the interhemispheric exchange of bacteria and viruses; however, data supporting the redistribution of parasites among continents are limited. In this study, the hypothesis that migratory birds contribute to the redistribution of parasites between continents was tested by sampling northern pintails (Anas acuta) at locations throughout the North Pacific Basin in North America and East Asia for haemosporidian infections and assessing the genetic evidence for parasite exchange. Of 878 samples collected from birds in Alaska (USA), California (USA), and Hokkaido (Japan) during August 2011-May 2012 and screened for parasitic infections using molecular techniques, Leucocytozoon, Haemoproteus, and Plasmodium parasites were detected in 555 (63%), 44 (5%), and 52 (6%) samples, respectively. Using an occupancy modeling approach, the probability of detecting parasites via replicate genetic tests was estimated to be high (ρ > 0.95). Multi-model inference supported variation of Leucocytozoon parasite prevalence by northern pintail age class and geographic location of sampling in contrast to Haemoproteus and Plasmodium parasites for which there was only support for variation in parasite prevalence by sampling location. Thirty-one unique mitochondrial DNA haplotypes were detected among haematozoa infecting northern pintails including seven lineages shared between samples from North America and Japan. The finding of identical parasite haplotypes at widely distributed geographic locations and general lack of genetic structuring by continent in phylogenies for Leucocytozoon and Plasmodium provides evidence for intercontinental genetic exchange of haemosporidian parasites. Results suggest that migratory birds, including waterfowl, could therefore facilitate the introduction of avian malaria and other haemosporidia to novel hosts and spatially distant regions.

Conservation genetics of high-arctic Gull species at risk: II. Diversity in the mtDNA control region of Threatened Ross’s Gull (Rhodostethia rosea)

Ross’s Gull (Rhodostethia rosea) is the rarest of Canadian high-arctic gulls, and is listed as Threatened under Canada’s Species-At-Risk Act. The large majority of birds breed in Siberia: the origins and affinities of four extremely small breeding colonies observed since 1978 in the Canadian high arctic are unknown. We compared a 515-bp region of the mtDNA Control Region amplified from material in museum collections taken from non-breeding birds in Canada (n = 8) and Alaska (n = 6), the latter passage migrants from the Siberian populations. The Alaskan birds all have distinct haplotypes that differ by as many as six SNPs: Canadian birds taken in the vicinity of the breeding colonies show only two of these. We hypothesize the origins of the Canadian breeding colonies as recent founder events by small numbers of passage migrants from Siberia via Alaska. Ross’s Gull maintains a very tenuous breeding presence in the Canadian high Arctic.

Conservation genetics of high-arctic Gull species at risk: I. Diversity in the mtDNA control region of circumpolar populations of the Endangered Ivory Gull (Pagophila eburnea)

The high-arctic Ivory Gull (Pagophila eburnea) has recently undergone a sharp decline in numbers, and in Canada it is listed as “Endangered” under the Species-At-Risk Act. To test for circumpolar genetic distinctiveness, we examined 264 bp of the mtDNA Control Region Domain I from 127 museum specimens collected during the breeding season from northern Canada, Greenland, and Norway, and during the non-breeding season from adjacent overwintering grounds in Canada, Greenland, and a disjunct area in Alaska adjacent to the Bering Sea. Partition of genetic variance according to various phylogeographic and breeding ground models indicates no strong population structure, except that Alaska birds are consistently differentiated from other locations, and there are significant temporal shifts in haplotype frequencies. The evidence suggests that Ivory Gulls in Canada, Greenland, and Norway are a single genetic entity, in contrast to Alaska birds, which may represent a distinctive Siberian population.

Geographic variation in migration chronology and winter distribution of midcontinent greater white-fronted geese

We evaluated spatial and temporal differences in migratory behavior among different breeding groups of midcontinent greater white-fronted geese (Anser albifrons) using band-recovery data and observations of neck collared geese during migration and winter. Birds from different breeding areas were initially delineated by geographic distance into 6 banding reference areas (BRAs): 1) interior Alaska, 2) North Slope of Alaska, 3) western Northwest Territories (NWT), 4) western Nunavut, 5) central Nunavut, and 6) eastern Nunavut. The banding groups also differed by breeding habitat, with geese from interior Alaska nesting in the boreal forest (taiga), and all other groups breeding in tundra habitats. Geese from interior Alaska migrated earlier during autumn, and were more likely to winter farther south (in Mexico) than geese from other breeding areas. Geese banded in central and eastern Nunavut (Queen Maud Gulf and Inglis River) wintered farther east (in Louisiana) than geese from other breeding areas. Small-scale (within-state) geographic segregation of wintering flocks was evidenced by the recent (post-1990) nearly exclusive use of a new wintering area in north central Texas by geese from interior Alaska. Segregation among BRAs was also apparent in Mexico, where taiga geese were found predominantly in the central Highlands (states of Zacatecas and Durango), whereas tundra geese mostly used states along the Gulf Coast (primarily Tamaulipas). Interior Alaska birds initiated spring migration earlier than geese from other areas, and were more likely than others to stop in the Rainwater Basin of Nebraska, a region where cholera outbreaks periodically kill thousands of geese. Geese from interior Alaska were the first to arrive at spring staging areas in prairie Canada where BRAs exhibited spatial delineation (a longitudinal cline) in relation to breeding areas. Our results show significant geographic and temporal variation among taiga and tundra breeding cohorts during autumn, winter, and spring. Temporal and spatial differences in migratory behavior may allow management practices that accommodate potential demographic differences between taiga and tundra populations. © 2013 The Wildlife Society.

Genetic diversity and mutation of avian paramyxovirus serotype 1 (Newcastle disease virus) in wild birds and evidence for intercontinental spread

Avian paramyxovirus serotype 1 (APMV-1), or Newcastle disease virus, is the causative agent of Newcastle disease, one of the most economically important diseases for poultry production worldwide and a cause of periodic epizootics in wild birds in North America. In this study, we examined the genetic diversity of APMV-1 isolated from migratory birds sampled in Alaska, Japan, and Russia and assessed the evidence for intercontinental virus spread using phylogenetic methods. Additionally, we predicted viral virulence using deduced amino acid residues for the fusion protein cleavage site and estimated mutation rates for the fusion gene of class I and class II migratory bird isolates. All 73 isolates sequenced as part of this study were most closely related to virus genotypes previously reported for wild birds; however, five class II genotype I isolates formed a monophyletic clade exhibiting previously unreported genetic diversity, which met criteria for the designation of a new sub-genotype. Phylogenetic analysis of wild-bird isolates provided evidence for intercontinental virus spread, specifically viral lineages of APMV-1 class II genotype I sub-genotypes Ib and Ic. This result supports migratory bird movement as a possible mechanism for the redistribution of APMV-1. None of the predicted deduced amino acid motifs for the fusion protein cleavage site of APMV-1 strains isolated from migratory birds in Alaska, Japan, and Russia were consistent with those of previously identified virulent viruses. These data therefore provide no support for these strains contributing to the emergence of avian pathogens. The estimated mutation rates for fusion genes of class I and class II wild-bird isolates were faster than those reported previously for non-virulent APMV-1 strains. Collectively, these findings provide new insight into the diversity, spread, and evolution of APMV-1 in wild birds.

Macroscopic, Histologic, and Ultrastructural Lesions Associated With Avian Keratin Disorder in Black-Capped Chickadees (Poecile atricapillus)

An epizootic of beak abnormalities (avian keratin disorder) was recently detected among wild birds in Alaska. Here we describe the gross, histologic, and ultrastructural features of the disease in 30 affected adult black-capped chickadees (Poecile atricapillus). Grossly, there was elongation of the rhamphotheca, with varying degrees of lateral deviation, crossing, and gapping between the upper and lower beak. Not uncommonly, the claws were overgrown, and there was alopecia, scaling, and crusting of the skin. The most prominent histopathologic features in the beak included epidermal hyperplasia, hyperkeratosis, and core-like intrusions of necrotic debris. In affected birds, particularly those with moderate to severe beak overgrowth, there was remodeling of premaxillary and mandibular bones and various dermal lesions. Lesions analogous to those found in beaks were present in affected claws, indicating that this disorder may target both of these similar tissues. Mild to moderate hyperkeratosis occurred in other keratinized tissues, including skin, feather follicles, and, occasionally, sinus epithelium, but typically only in the presence of microbes. We did not find consistent evidence of a bacterial, fungal, or viral etiology for the beak lesions. The changes observed in affected birds did not correspond with any known avian diseases, suggesting a potentially novel hyperkeratotic disorder in wild birds.

Endogenous control of migratory behavior in Alaskan Northern Wheatears Oenanthe oenanthe

We tested endogenous migratory fuelling and nocturnal migratory restlessness in juvenile Northern Wheatears (Oenanthe oenanthe) from Alaska kept in captivity indoors. The birds showed a spontaneous seasonal, and biologically relevant, pattern of body mass development and nocturnal migratory restlessness. These data were compared to similar data of Northern Wheatears from Iceland. The Alaskan birds showed much higher restlessness but lower fuelling, which is consistent with their much longer journey but different ecological encounters.

Cross-hemisphere migration of a 25 g songbird

The northern wheatear (Oenanthe oenanthe) is a small (approx. 25 g), insectivorous migrant with one of the largest ranges of any songbird in the world, breeding from the eastern Canadian Arctic across Greenland, Eurasia and into Alaska (AK). However, there is no evidence that breeding populations in the New World have established overwintering sites in the Western Hemisphere. Using light-level geolocators, we demonstrate that individuals from these New World regions overwinter in northern sub-Sahara Africa, with Alaskan birds travelling approximately 14 500 km each way and an eastern Canadian Arctic bird crossing a wide stretch of the North Atlantic (approx. 3500 km). These remarkable journeys, particularly for a bird of this size, last between one to three months depending on breeding location and season (autumn/spring) and result in mean overall migration speeds of up to 290 km d(-1). Stable-hydrogen isotope analysis of winter-grown feathers sampled from breeding birds generally support the notion that Alaskan birds overwinter primarily in eastern Africa and eastern Canadian Arctic birds overwinter mainly in western Africa. Our results provide the first evidence of a migratory songbird capable of linking African ecosystems of the Old World with Arctic regions of the New World.

Contour-feather moult of Bar-tailed Godwits (Limosa lapponica baueri) in New Zealand and the northern hemisphere reveals multiple strategies by sex and breeding region

The extreme long-distance migration of Alaskan breeding Bar-tailed Godwits (Limosa lapponica baueri) may present severe constraints on annual moult, and high individual variation in plumage and migration timing suggests that multiple strategies by sex and breeding region may exist. We used digital photography of free-living Bar-tailed Godwits to describe the timing and extent of pre-basic and pre-breeding contour-feather moults in New Zealand, and used plumage of breeding birds in Alaska to infer the proportion of moults occurring in Alaska and Asia. These data demonstrated that: (1) Godwits conducted overlapping pre-alternate and pre-supplemental moults; (2) pre-basic and pre-breeding moults were scheduled differently in relation to southbound and northbound migration respectively; (3) northern and southern Alaskan breeding Godwits of each sex were distinguishable by plumage differences throughout the non-breeding season; and (4) males and northern breeders achieved more extensive breeding plumage by spending longer in pre-breeding moult in New Zealand, rather than through faster moult rates or greater investment in moult during migratory stopover in Asia. The existence of a ventral pre-supplemental moult implies that contemporary selection for red breeding plumage overrides older selection for barred alternate plumage. Our use of individual-based data revealed a continuum of annual moult strategies within the population, which may reflect individual differences in any combination of sex, size, migration distance or breeding location. Even within the highly constrained annual cycle of extreme long-distance migrants, differential selection influences how individuals manage trade-offs among non-breeding activities such as moult, fuelling and migration.

Microanatomy of passerine hard‐cornified tissues: Beak and claw structure of the black‐capped chickadee (Poecile atricapillus)

The microanatomy of healthy beaks and claws in passerine birds has not been well described in the literature, despite the importance of these structures in avian life. Histological processing of hard-cornified tissues is notoriously challenging and only a few reports on effective techniques have been published. An emerging epizootic of beak deformities among wild birds in Alaska and the Pacific Northwest region of North America recently highlighted the need for additional baseline information about avian hard-cornified structures. In this study, we examine the beak and claw of the Black-capped Chickadee (Poecile atricapillus), a common North American passerine that is affected by what has been described as "avian keratin disorder." We use light and scanning electron microscopy and high-magnification radiography to document the healthy microanatomy of these tissues and identify features of functional importance. We also describe detailed methods for histological processing of avian hard-cornified structures and discuss the utility of special stains. Results from this study will assist in future research on the functional anatomy and pathology of hard-cornified structures and will provide a necessary reference for ongoing investigations of avian keratin disorder in Black-capped Chickadees and other wild passerine species.

Prevalence of Hematozoa Infections Among Breeding and Wintering Rusty Blackbirds

Abstract. The Rusty Blackbird (Euphagus carolinus) has declined precipitously over the past several decades, and stressors on both the breeding and wintering grounds are suspected causes. Over 3 years, we collected blood samples from breeding birds in Alaska and Maine and from wintering birds in Mississippi and Arkansas to determine the prevalence of hematozoan infections at different times of the year. The prevalence of hematozoa (percent of birds infected) in Alaska was 44% of 43 birds, lower than previously reported from Newfoundland and Ontario (83% of 23 birds). Blood parasites were found among 67% of 12 Rusty Blackbirds sampled in Maine, not different from the prevalence in Newfoundland and Ontario. Leucocytozoon was the most common parasite; few breeding birds were infected with Plasmodium or Trypanosoma sp. During the winter in Mississippi and Arkansas, the overall prevalence of hematozoa was 49% over three years. In winter as in summer, Leucocytozoon was the most commonly encountered parasite (n ...

Epizootic of Beak Deformities Among Wild Birds in Alaska: An Emerging Disease in North America?

ABSTRACT. The sudden appearance of a large cluster of animals with gross abnormalities may signal a significant change in an ecosystem. We describe an unusual concentration of beak deformities that appear to have arisen rapidly within Alaska and now extend southward along the Pacific Coast. In Alaska we have documented 2,160 Black-capped Chickadees (Poecile atricapillus) and 435 individuals of 29 other species of birds, primarily during the past decade, with grossly overgrown and often crossed beaks. The annual prevalence of beak abnormalities among adult Black-capped Chickadees in south-central Alaska varied from 3.6% to 9.7% and averaged 6.5 ± 0.5% between 1999 and 2008. Only 0.05 ± 0.05% of nestlings and 0.3 ± 0.2% of juveniles <6 months old had abnormal beaks, which suggests that this is either a latent developmental or an acquired condition. We documented 80 cases in which a Black-capped Chickadee captured with an apparently normal beak was subsequently recaptured with a beak abnormality and 8 cases ...

Seasonal and population variation in male testosterone levels in breeding orange-crowned warblers ( Vermivora celata)

Comparative hormone studies can reveal how physiology underlies life history variation. Here, we examined seasonal variation in plasma testosterone concentration between populations of male orange-crowned warblers ( Vermivora celata) breeding in Fairbanks, Alaska ( V. c. celata) and on Santa Catalina Island, California ( V. c. sordida). These populations face different ecological constraints and exhibit different life histories. Alaska birds have a short breeding season, low annual adult survival, and high reproductive rates. In contrast, Catalina Island birds exhibit high adult survival and low reproductive rates despite having a long breeding season. We examined seasonal variation in male testosterone concentrations as a potential mechanism underlying differences in male reproductive strategies between populations. From 2006 to 2008, we sampled males during the pre-incubation, incubation, and nestling stages. Alaska males exhibited a seasonal testosterone pattern typical of northern passerines: testosterone levels were high during pre-incubation and declined during incubation to low levels during nestling provisioning. Testosterone concentrations in Catalina Island males, however, did not vary consistently with breeding stage, remained elevated throughout the breeding season, and were higher than in Alaska males during the nestling stage. We hypothesize that in Alaska, where short seasons and high adult mortality limit breeding opportunities, the seasonal testosterone pattern facilitates high mating effort prior to incubation, but high parental investment during the nestling stage. On Catalina Island, elevated testosterone levels may reflect the extended mating opportunities and high population density facing males in this population. Our results suggest that population variation in seasonal testosterone patterns in orange-crowned warblers may be a function of differences in life history strategy and the social environment.