Paul L. Flint

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.

Genetic evidence of intercontinental movement of avian influenza in a migratory bird: the northern pintail (Anas acuta)

The role of migratory birds in the movement of the highly pathogenic (HP) avian influenza H5N1 remains a subject of debate. Testing hypotheses regarding intercontinental movement of low pathogenic avian influenza (LPAI) viruses will help evaluate the potential that wild birds could carry Asian‐origin strains of HP avian influenza to North America during migration. Previous North American assessments of LPAI genetic variation have found few Asian reassortment events. Here, we present results from whole‐genome analyses of LPAI isolates collected in Alaska from the northern pintail (Anas acuta), a species that migrates between North America and Asia. Phylogenetic analyses confirmed the genetic divergence between Asian and North American strains of LPAI, but also suggested inter‐continental virus exchange and at a higher frequency than previously documented. In 38 isolates from Alaska, nearly half (44.7%) had at least one gene segment more closely related to Asian than to North American strains of LPAI. Additionally, sequences of several Asian LPAI isolates from GenBank clustered more closely with North American northern pintail isolates than with other Asian origin viruses. Our data support the role of wild birds in the intercontinental transfer of influenza viruses, and reveal a higher degree of transfer in Alaska than elsewhere in North America.

Estimating prefledging survival: allowing for brood mixing and dependence among brood mates

Estimates of juvenile survival from hatch to fledging provide important information on waterfowl productivity. We develop a model for estimating survival of young waterfowl from hatch to fledging. Our model enables interchange of individuals among broods and relaxes the assumption that individuals within broods have independent survival probabilities. The model requires repeated observations of individually identifiable adults and their offspring that are not individually identifiable. A modified Kaplan-Meier procedure (Pollock et al. 1989a,b) and a modified Mayfield procedure (Mayfield 1961, 1975; Johnson 1979) can be used under this general modeling framework, and survival rates and corresponding variances of the point estimators can be determined.

Reproductive implications of egg-size variation in the black brant

-We analyzed variation in egg size of Black Brant (Branta bernicla nigricans) in relation to clutch size, laying date, female age, year, and position in the laying sequence. A total of 3,478 eggs was measured over three years. Egg size increased with clutch size and female age, and decreased with laying date, year, and position in the laying sequence. We did not detect a negative phenotypic correlation between clutch size and egg size. However, overlap in total clutch volumes for clutches of different sizes indicated trade offs occurred among individuals with comparable investments in their clutches. Received 1 October 1991, accepted 30 March 1992. THE COMBINATION of clutch size and egg size determines the total energetic investment in clutch formation by a laying female. Egg size may affect female fitness through its effects on initial size, early growth and survivorship of hatchlings (Cole 1979, Ankney 1980, Thomas and Brown 1988, Sedinger and Flint 1991), whereas clutch size is related to fitness via its effect on the potential number of offspring produced (Lessells 1986). Arctic-nesting geese rely heavily on stored lipid and protein reserves for egg production and incubation (Ankney and MacInnes 1978, Raveling 1979, Ankney 1984). Thus, nutrients available for a clutch are limited and at least partially predetermined when geese arrive on the breeding grounds. This limitation on reproductive investment, combined with the fitness advantages of both large clutches and large eggs, creates the potential for both ultimate and proximate trade offs between clutch size and

Avian influenza at both ends of a migratory flyway: characterizing viral genomic diversity to optimize surveillance plans for North America

Although continental populations of avian influenza viruses are genetically distinct, transcontinental reassortment in low pathogenic avian influenza (LPAI) viruses has been detected in migratory birds. Thus, genomic analyses of LPAI viruses could serve as an approach to prioritize species and regions targeted by North American surveillance activities for foreign origin highly pathogenic avian influenza (HPAI). To assess the applicability of this approach, we conducted a phylogenetic and population genetic analysis of 68 viral genomes isolated from the northern pintail (Anas acuta) at opposite ends of the Pacific migratory flyway in North America. We found limited evidence for Asian LPAI lineages on wintering areas used by northern pintails in California in contrast to a higher frequency on breeding locales of Alaska. Our results indicate that the number of Asian LPAI lineages observed in Alaskan northern pintails, and the nucleotide composition of LPAI lineages, is not maintained through fall migration. Accordingly, our data indicate that surveillance of Pacific Flyway northern pintails to detect foreign avian influenza viruses would be most effective in Alaska. North American surveillance plans could be optimized through an analysis of LPAI genomics from species that demonstrate evolutionary linkages with European or Asian lineages and in regions that have overlapping migratory flyways with areas of HPAI outbreaks.

Density-dependent effects on growth, body size, and clutch size in black brant

-We documented gosling size in late summer, adult body size, and clutch size of known-age Black Brant (Branta bernicla nigricans) females nesting on the Tutakoke River colony between 1986 and 1995. During this period, the colony increased from 1,100 to >5,000 nesting pairs. Gosling mass at 30 days of age declined from 764 + SE of 13 g and 723 ? 15 g for males and females, respectively, in the 1986 cohort, to 665 + 18 g and 579 ? 18 g in the 1994 cohort. Gosling size was directly negatively correlated with number of Black Brant broods. We detected no trend in adult body size for individuals from these cohorts; in fact, adults from the 1992 and 1994 cohorts had the largest overall masses. Clutch size increased with age from 3.4 eggs for 2-year-old females to 4.4 eggs for 5-year-old females. Clutch size declined during the study by 0.20 (3-year-old females) to 0.45 (2-year-old females) eggs. Clutch size did not decline between the 1986 and 1990 cohorts for females that were >5 years old. Our results for clutch size and gosling size are similar to those recorded for Lesser Snow Geese (Chen caerulescens caerulescens). Our failure to detect a trend in adult body size, however, differs from the response of other geese to increasing population density. We interpret this difference in effects of density on adult size between Black Brant and other geese as an indication of stronger selection against the smallest individuals in Black Brant relative to other species of geese. Received 19 May 1997, accepted 17 November 1997. ARCTIC-NESTING GEESE are strictly herbivorous during the breeding season (Owen 1980, Sedinger 1992) and are selective of the most nutritious foods and habitats containing these foods (Lieff 1973, Harwood 1975, Sedinger and Raveling 1984, Gadallah and Jefferies 1995a, b). Despite these strong preferences, substantial variation exists in growth rates of goslings, which likely is associated with temporal and spatial variation in habitat quality (Cooch et al. 1991a, Larsson and Forslund 1991, Sedinger and Flint 1991, Aubin et al. 1993). Because gosling growth is associated with future survival and fecundity (Larsson and Forslund 1991, 1992, Francis et al. 1992, Rockwell et al. 1993, Sedinger et al. 1995b), habitat quality likely is directly linked to processes determining population dynamics. Sedinger and Raveling (1986) argued that seasonal declines in nutrient I E-mail: ffjss@aurora.alaska.edu 2 Present Address: Institute for Wetland and Waterfowl Research, Ducks Unlimited Inc., One Waterfowl Way, Memphis, Tennessee 38120, USA. 3Present Address: Alaska Science Center, Division of Biological Resources, U.S. Geological Survey, 1011 East Tudor Road, Anchorage, Alaska 99503, USA. concentration in the diet of Cackling Canada Geese (B. canadensis minima) resulted from reduced availability of the highest-quality foods because of grazing by geese. Lesser Snow Geese (Chen caerulescens caerulescens) substantially reduce the abundance of preferred food plants (Cargill and Jefferies 1984, Hik and Jefferies 1990), as do some Black Brant (B. bernicla nigricans; hereafter brant; Person et al. 1998). The relationship between nutrient intake by goslings and demographic parameters creates the potential for per capita availability of foods of sufficient quality during brood rearing to influence population dynamics. Long-term declines in body size and fecundity have been associated with increased size of a colony of Lesser Snow Geese, and Cooch et al. (1991a, b) and Francis et al. (1992) demonstrated a decline in juvenile survival for this colony over the same period. The number of brant nesting on the YukonKuskokwim (Y-K) Delta declined by more than 60% in the 1970s and early 1980s (Sedinger et al. 1993), likely as a result of human harvest (Sedinger 1996) and predation by arctic foxes (Alopex lagopus; Anthony et al. 1991, Sedinger et al. 1993). Reduced predation and harvest were as-

Intercontinental reassortment and genomic variation of low pathogenic avian influenza viruses isolated from northern pintails ( Anas acuta ) in Alaska: examining the evidence through space and time

Migration and population genetic data for northern pintails (Anas acuta) and phylogenetic analysis of low pathogenic avian influenza (LPAI) viruses from this host in Alaska suggest that northern pintails are involved in ongoing intercontinental transmission of avian influenza. Here, we further refine this conclusion through phylogenetic analyses which demonstrate that detection of foreign lineage gene segments is spatially dependent and consistent through time. Our results show detection of foreign lineage gene segments to be most likely at sample locations on the Alaska Peninsula and least likely along the Southern Alaska Coast. Asian lineages detected at four gene segments persisted across years, suggesting maintenance in avian hosts that migrate to Alaska each year from Asia or in hosts that remain in Alaska throughout the year. Alternatively, live viruses may persist in the environment and re-infect birds in subsequent seasons.

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.

Effects of harness-attached transmitters on premigration and reproduction of brant

Radio transmitters are an important tool in waterfowl ecology studies, but little is known about their effects on free-ranging geese. We attached transmitters to female brant (Branta bernicla nigricans) to investigate migration schedules at a fall staging area, return rates to nesting grounds, and nesting rates of returning females in subsequent breeding seasons. Radio-tagged females (n = 62) carried either 35-g back-mounted transmitters attached with ribbon harnesses, or 26 or 32-g back-mounted transmitters affixed with plastic-coated wire harnesses (Dwyer 1972). Arrival and departure schedules at Izembek Lagoon, Alaska, did not differ (P > 0.05) between radio-tagged females and the entire population in 1987-89. Color-banded females with transmitters returned to the breeding colony in subsequent nesting seasons (1988-92) at a lower (P ≤ 0.003) rate (≤4%) than color-banded females without transmitters (57-83%). The 1 returning color-banded female with a transmitter did not breed, while an average 90% of the returning color-banded females without transmitters nested in subsequent breeding seasons (P = 0.005). Back-mounted, harness-attached transmitters may bias data in studies of waterfowl behavior, productivity, and survival

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.