Margaret R. Petersen

Prevalence of Influenza A viruses in wild migratory birds in Alaska: Patterns of variation in detection at a crossroads of intercontinental flyways

BackgroundThe global spread of the highly pathogenic avian influenza H5N1 virus has stimulated interest in a better understanding of the mechanisms of H5N1 dispersal, including the potential role of migratory birds as carriers. Although wild birds have been found dead during H5N1 outbreaks, evidence suggests that others have survived natural infections, and recent studies have shown several species of ducks capable of surviving experimental inoculations of H5N1 and shedding virus. To investigate the possibility of migratory birds as a means of H5N1 dispersal into North America, we monitored for the virus in a surveillance program based on the risk that wild birds may carry the virus from Asia.ResultsOf 16,797 birds sampled in Alaska between May 2006 and March 2007, low pathogenic avian influenza viruses were detected in 1.7% by rRT-PCR but no highly pathogenic viruses were found. Our data suggest that prevalence varied among sampling locations, species (highest in waterfowl, lowest in passerines), ages (juveniles higher than adults), sexes (males higher than females), date (highest in autumn), and analytical technique (rRT-PCR prevalence = 1.7%; virus isolation prevalence = 1.5%).ConclusionThe prevalence of low pathogenic avian influenza viruses isolated from wild birds depends on biological, temporal, and geographical factors, as well as testing methods. Future studies should control for, or sample across, these sources of variation to allow direct comparison of prevalence rates.

At-sea distribution of spectacled eiders : A 120-year-old mystery resolved

The at-sea distribution of the threatened Spectacled Eider (Somateriafischeri) has remained largely undocumented. We identified migration corridors, staging and molting areas, and wintering areas of adult Spectacled Eiders using implanted satellite transmitters in birds from each of the three extant breeding grounds (North Slope and Yukon-Kuskokwim Delta in Alaska and arctic Russia). Based on transmitter locations, we conducted aerial sur- veys to provide visual confirmation of eider flocks and to estimate numbers of birds. We identified two principal molting and staging areas off coastal Alaska (Ledyard Bay and east- ern Norton Sound) and two off coastal Russia (Mechigmenskiy Bay on the eastern Chukotka Peninsula, and the area between the Indigirka and Kolyma deltas in the Republic of Sakha). We estimated that >10,000 birds molt and stage in monospecific flocks at Mechigmenskiy and Ledyard bays, and several thousand molt and stage in eastern Norton Sound. We further identified eastern Norton Sound as the principal molting and staging area for females nest- ing on the Yukon-Kuskokwim Delta, and Ledyard Bay and Mechigmenskiy Bay as the prin- cipal molting and staging areas for females nesting on the North Slope. Males marked at all three breeding grounds molt and stage in Mechigmenskiy Bay, Ledyard Bay, and the Indi- girka-Kolyma delta region. Males from the Yukon-Kuskokwim Delta molt and stage mainly at Mechigmenskiy Bay. Equal numbers of males from the North Slope molt and stage at all three areas, and most males from arctic Russia molt and stage at the Indigirka-Kolyma delta region. Postbreeding migration corridors were offshore in the Bering, Chukchi, and Beaufort seas. In winter, eiders were in the Bering Sea south of St. Lawrence Island. Our estimates from surveys in late winter and early spring suggest that at least 333,000 birds winter in

Relative effects of survival and reproduction on the population dynamics of emperor geese

Populations of emperor geese (Chen canagica) in Alaska declined sometime between the mid1960s and the mid-1980s and have increased little since. To promote recovery of this species to former levels, managers need to know how much their perturbations of survival and/or reproduction would affect population growth rate (X). We constructed an individual-based population model to evaluate the relative effect of altering mean values of various survival and reproductive parameters on X and fall age structure (AS, defined as the proportion of juv), assuming additive rather than compensatory relations among parameters. Altering survival of adults had markedly greater relative effects on A than did equally proportionate changes in either juvenile survival or reproductive parameters. We found the opposite pattern for relative effects on AS. Due to concerns about bias in the initial parameter estimates used in our model, we used 5 additional sets of parameter estimates with this model structure. We found that estimates of survival based on aerial survey data gathered each fall resulted in models that corresponded more closely to independent estimates of A than did models that used mark-recapture estimates of survival. This disparity suggests that mark-recapture estimates of survival are biased low. To further explore how parameter estimates affected estimates of X, we used values of survival and reproduction found in other goose species, and we examined the effect of an hypothesized correlation between an individuals clutch size and the subsequent survival of her young. The rank order of parameters in their relative effects on A was consistent for all 6 parameter sets we examined. The observed variation in relative effects on A among the 6 parameter sets is indicative of how relative effects on A may vary among goose populations. With this knowledge of the relative effects of survival and reproductive parameters on A, managers can make more informed decisions about which parameters to influence through management or to target for future study. J. WILDL. MANAGE. 61(1):191-201

Use of implanted satellite transmitters to locate spectacled eiders at-sea

Population estimates of Spectacled Eiders (Somateria fischeri) on the Yukon-Kuskokwim Delta (YKD), Alaska, suggest that by 1992 the number of birds nesting on this major nesting area had declined to 1,721 pairs, 4% of that estimated in the 1970s (Stehn et al. 1993). Consequently, Spectacled Eiders were listed as threatened under the Endangered Species Act. As nesting habitats for this species are believed to have changed little over the past 100 years, hypotheses concerning the cause of this decline include factors away from nesting areas. The non-nesting distribution of this eider is unknown, but birds are believed to molt and winter in the Bering and Chukchi seas (Dau and Kistchinski 1977). Systematic aerial surveys to locate areas where birds concentrate are expensive because of the vast area to be surveyed and dangerous because of restricted daylight and extreme weather conditions. Surveys from ships along the ice margin in the Bering Sea failed to locate concentrations of birds (Irving et al. 1968, Everett et al. 1989). We initiated a study to determine if at-sea areas used by Spectacled Eiders could be identified using satellite telemetry.

Yolk formation in some Charadriiform birds

By counting and measuring the major ova of breeding birds at autopsy and combining these data with time intervals between ovipositions, rough estimates have been made of the time required to form yolk in some non-captive birds (King 1973). Direct studies have been made in domestic fowl (Gallus gallus var. domesticus; Gilbert 1972), turkeys (Meleagris gallopavo; Bacon and Cherms 1968), and Common Quail (Coturnix coturnix; Bacon and Koontz 1971), by feeding the birds a capsule containing dye each day, and counting dye rings in the yolks after the eggs have been hardcooked. Recently developed methods of fixing and staining eggs have revealed differences in yolk deposited during day and night, thus permitting another estimation of the number of days during which yolk was deposited, and without direct contact with the female (Grau 1976). In eggs from chickens and quail that had been fed dyes, yolk that stained darkly with dichromate was shown to be deposited during the active daytime feeding periods, while pale-staining yolk was deposited during the night. Thus, pairs of light and dark rings, which together take a day to be deposited, may be counted to estimate time of yolk formation. In the present study we have applied the yolk ring method of estimating the number of days during which the bulk of the yolk is deposited around the central white core (Grau 1976) to the eggs of some shorebirds, gulls, terns and alcids.

Annual survival and site fidelity of Steller's eiders molting along the Alaska Peninsula

Populations of Stellers eiders (Polysticta stelleri) molting and wintering along the Alaska Peninsula have decliued since the 1960s. We captured and marked a large sample of Stellers eiders molting in 2 lagoons along the Alaska Peninsula between 1975-97. We used mark-recapture analysis techniques to estimate annual survival and movement probabilitics within and among lagoons for male and female eiders. Estimates of annual survival (±SE) were 0.899 = 0.032 for females and 0.765 = 0.044 for males. Both sexes showed high rates of fidelity to specific molting locations (>95%) within lagoons: yet we found no evidence that aunual probability of survival differed among groups molting in different locations either within or among lagoons. We found weak evidence that annual survival decreased between the periods 1975-81 and 1991-97. The lower survival of males compared to females is unusual for waterfowl and may result in a female-biased sex ratio. We conclude that a decrease in adult survival may have mitiated the long-term population decline. Further, a shortage of males may be limiting reproductive potential.

Effect of lead poisoning on spectacled eider survival rates

Spectacled eider (Somateria fischeri) populations on the Yukon-Kuskokwim Delta (Y-K Delta), Alaska, declined rapidly through the 1980s, and low adult female survival was suggested as the likely cause of the decline. We used mark-resighting techniques to study annual survival rates of adult female spectacled eiders at 2 sites on the Y-K Delta during 1993-96. Our data suggest survival rates may differ among sites. However, a model fit to a subset of data on females for which we knew lead levels in blood suggests lead exposure influences survival. Adult females exposed to lead prior to hatching their eggs survived at a much lower rate (0.44 ± 0.10) each year than females not exposed to lead before hatch (0.78 ± 0.05). We suggest most mortality from lead exposure occurs over winter, and the related reduction in adult survival may be impeding recovery of local populations. We encourage managers to curtail input of lead shot into the environment.

LACK OF SPATIAL GENETIC STRUCTURE AMONG NESTING AND WINTERING KING EIDERS

Abstract The King Eider (Somateria spectabilis) has been delineated into two broadly distributed breeding populations in North America (the western and eastern Arctic) on the basis of banding data and their use of widely separated Pacific and Atlantic wintering areas. Little is known about the level of gene flow between these two populations. Also unknown is whether behavioral patterns common among migratory waterfowl, such as site fidelity to wintering areas and pair formation at these sites, have existed for sufficient time to create a population structure defined by philopatry to wintering rather than to nesting locations. We used six nuclear microsatellite DNA loci and cytochrome b mitochondrial DNA sequence data to estimate the extent of spatial genetic differentiation among nesting and wintering areas of King Eiders across North America and adjacent regions. Estimates of interpopulation variance in microsatellite allele and mtDNA haplotype frequency were both low and nonsignificant based on samples from three wintering and four nesting areas. Results from nested clade analysis, mismatch distributions, and coalescent-based analyses suggest historical population growth and gene flow that collectively may have homogenized gene frequencies. The presence of several unique mtDNA haplotypes among birds wintering near Greenland suggests that gene flow may now be more limited between the western and eastern Arctic, which is consistent with banding data. Ausencia de Estructura Genética Espacial entre Áreas de Nidificación e Invernada en Somateria spectabilis Resumen. Con base en datos de anillamiento y en el uso de áreas de invernada separadas en el Pacífico y el Atlántico, la especie Somateria spectabilis ha sido separada en dos poblaciones reproductivas de amplia distribución en Norte América (las del Ártico este y oeste). Se conoce poco sobre los niveles de flujo génico entre estas dos poblaciones. También se desconoce si patrones de comportamiento comunes entre aves acuáticas migratorias, como la fidelidad a los sitios de invernada y la formación de parejas en dichos sitios, han existido por suficiente tiempo como para crear estructura poblacional definida por la filopatría a las áreas de invernada en lugar de a las áreas de nidificación. Utilizamos seis loci nucleares de ADN microsatelital y secuencias del gen mitocondrial citocromo b para estimar el grado de diferenciación genética espacial entre áreas de nidificación e invernada de S. spectabilis a través de Norte América y regiones adyacentes. Los estimados de la varianza interpoblacional en la frecuencia de alelos de microsatélites y de haplotipos de ADNmt fueron bajos y no significativos con base en muestras de tres áreas de invernada y cuatro de nidificación. Los resultados de un análisis de clados anidados, de las distribuciones “mismatch” y de análisis basados en coalescencia sugieren la existencia de crecimiento poblacional histórico y flujo génico, eventos que colectivamente podrían haber homogeneizado las frecuencias génicas. La presencia de varios haplotipos exclusivos entre aves que invernan cerca de Groenlandia sugiere que el flujo génico podría ser ahora más limitado entre el Ártico oeste y este, lo que es consistente con los datos de anillamiento.

Populations, Feeding Ecology and Molt of Steller's Eiders

-This study considers the temporal and spatial distribution of Stellers Eiders (Polysticta stelleri) during molt along the north side of the Alaska Peninsula from Port Heiden to Bechevin Bay. Subadult eiders molted primarily at Nelson Lagoon, adult males at Nelson Lagoon and Izembek Bay, and adult females primarily at Izembek Bay. Only a few eiders used Bechevin Bay, Seal Islands, and Port Heiden. Although the flightless period overlapped among different age and sex classes, subadults were flightless first, then adult males, and last, adult females. Eiders maintained spatial and temporal separation during the flightless period, thereby reducing competition for food

POPULATION STRUCTURE OF PACIFIC COMMON EIDERS BREEDING IN ALASKA

Abstract We used satellite telemetry to study the migration routes and wintering areas of two allopatric breeding populations of Pacific Common Eiders (Somateria mollissima v-nigrum) in Alaska: the Yukon-Kuskokwim Delta, and the western Beaufort Sea coast. Only 6% (2 of 36) of females wintered within the wintering area of the other breeding population. Both breeding populations wintered in the closest available ice-free habitat, perhaps to minimize migratory distance. Two Beaufort Sea females wintered in areas used by Yukon-Kuskokwim Delta females, implying potential gene flow among breeding areas. Yet, we conclude that these two populations are largely geographically isolated throughout the annual cycle and the environmental factors influencing survival and reproduction likely differ between these groups of birds. Thus, regardless of the potential gene flow among breeding populations, we suggest that birds from these two breeding areas should be managed as separate populations. Estructura Poblacional Reproductiva de Somateria mollissima v-nigrum en Alaska Resumen. Usamos telemetría satelital para estudiar las rutas de migración y áreas de invernada de dos poblaciones alopáticas reproductivas de Somateria mollissima v-nigrum en Alaska: la del Delta Yukon-Kuskokwim, y la de la costa oeste del Mar de Beaufort. Solo el 6% (2 de 36) de las hembras invernaron dentro del área de invernada de la otra población reproductiva. Las dos poblaciones invernaron en el hábitat libre de hielo más cercano, tal vez para minimizar la distancia de migración. Dos hembras del Mar de Beaufort invernaron en áreas usadas por hembras del Delta de Yukon-Kuskokwim, implicando un potencial flujo génico entre las áreas de reproducción. Sin embargo, concluimos que estas dos poblaciones están aisladas geográficamente a lo largo del ciclo anual y que los factores ambientales que afectan la supervivencia y reproducción son probablemente diferentes entre estos grupos de aves. Por lo tanto, a pesar del flujo génico potencial entre las poblaciones reproductivas, sugerimos que las aves de estas dos áreas de reproducción deben ser manejadas como poblaciones separadas.