USGS Science⌕ Search
Home/Archive/USGS

USGS · 70175730

Population dynamics of Greater Scaup breeding on the Yukon-Kuskokwim Delta, Alaska

Paul L. Flint·J. Barry Grand·Thomas F. Fondell·Julie A. Morse
View original source ↗Export metadata ↓

Abstract

Populations of greater scaup ( Aythya marila ) remained relatively stable during a period when populations of lesser scaup ( A. affinis ) have declined from historic levels. To assist in describing these differences in population trends, from 1991 through 2000, we studied the survival, nesting ecology, and productivity of greater scaup on the Yukon-Kuskokwim Delta (Y-K Delta), Alaska, to develop a model of population dynamics. We located nests, radio-marked females for renesting studies, estimated duckling survival, and leg-banded females to examine nest site fidelity and annual survival. Greater scaup initiated egg laying later than other species, and most clutches (>80%) were initiated over 20 days each year. We located 1,056 nests; nest success ranged from 7 to 61 % among years. Following loss of their first clutch, 51 % of radio-tagged females attempted to renest. Duckling survival to 30 days of age was 37.5%. Our best model suggested that annual survival did not vary among years and averaged 81 %. Survival rate was positively related to structural body size. Only 8 of 214 banded individuals were reported as recovered (1 each in Maryland, Michigan, Minnesota, Washington, and Alaska and 3 in California). Using a stochastic model, we estimated that, on average, breeding females produced 0.57 young females/nesting season. We combined this estimate of productivity with our annual estimates of adult survival and an assumed population growth rate of 1.0, then solved for an estimate of first-year survival (0.40). Under these conditions the predicted stable age distribution of breeding females (i.e., the nesting population) was 15.1% 1-year-old, 4.1% 2-year-old first-time breeders, and 80.8% 2-year-old and older, experienced breeders. We subjected this stochastic model to perturbation analyses to examine the relative effects of demographic parameters on k. The relative effects of productivity and adult survival on the population growth rate were 0.26 and 0.72, respectively. Thus, compared to productivity, proportionally equivalent changes in annual survival would have 2.8 times the effect on k. However, when we examined annual variation in predicted population size using standardized regression coefficients, productivity explained twice as much variation as annual survival. Thus, management actions focused on changes in survival or productivity have the ability to influence population size; however, substantially larger changes in productivity are required to influence population trends.

Explore related subjects

Wildlife MonographsArticle

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Paul L. Flint, J. Barry Grand, Thomas F. Fondell, Julie A. Morse. 2006. Population dynamics of Greater Scaup breeding on the Yukon-Kuskokwim Delta, Alaska. https://doi.org/10.2193/0084-0173(2006)162%5B1%3Apdogsb%5D2.0.co%3B2

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related USGS reports

USGS2026

Ecology of reintroduced Rocky Mountain bighorn sheep in Dinosaur National Monument

Translocations have been widely used to restore and conserve bighorn sheep ( Ovis canadensis ) populations in North America. Some translocations have been successful, but many populations remain small and genetically isolated. Population structure can influence the viability and long-term success of reintroductions. Social ungulates often function as interconnected subpopulations (metapopulations); however, few studies evaluate subpopulation sizes, connectivity, and genetic diversity within metapopulations. To address this gap, we conducted a comprehensive study of a reintroduced Rocky Mountain bighorn sheep ( Ovis canadensis canadensis ) population in Dinosaur National Monument in Colorado and Utah, USA, between 2006–2020. We analyzed global positioning system (GPS) radio-collar data, genetic samples, and results of health testing to evaluate abundance, distribution, genetic structure and diversity, habitat use, movement and connectivity, and presence of or exposure to respiratory pathogens. We integrated these analyses to evaluate the outcomes of a reintroduction effort that began in 1952, over 70 years ago, and to inform management decisions in Dinosaur National Monument. We also provide a framework for evaluating metapopulation processes, including a non-invasive approach that links genetic structure with Bayesian spatial capture-recapture analyses to estimate subpopulation sizes. Despite models indicating continuous suitable habitat, we found a spatially structured population with at least 4 subpopulations with constrained connectivity. Evidence from step selection and density analyses suggested that movement among subpopulations may be limited by semi-permeable barriers including rivers and human disturbance, which could contribute to maintenance of spatial structure over time. In 2006, antibody to Mycoplasma ovipneumoniae was detected in all geographically and genetically distinct subpopulations. Widespread clinical signs of disease and a confirmed exposure to M. ovipneumoniae in 2019 indicate a long-term disease challenge. Proximity to domestic sheep creates repeated opportunities for introduction of new M. ovipneumoniae strains. We estimated abundance in 2019 at 109 (95% CrI = 87–133), composed of subpopulations ranging from 18–39 animals (95% CrIs from 11–50). Genetic diversity was relatively high compared to other reintroduced and native Rocky Mountain bighorn sheep populations, which is likely a consequence of multiple translocations from different sources. Three of 4 subpopulation centers generally aligned with the locations of original translocation release sites. Persistence in the presence of pathogens may be facilitated by metapopulation structure and moderately high genetic diversity. Conversely, metapopulation structure can also facilitate pathogen persistence. Our approach offers a path to advance understanding of the population ecology of reintroduced bighorn sheep and can inform effective conservation and management of their populations.

Colorado, Wyoming↗
USGS2026

Feathers and flu: Identifying data gaps in avian influenza host dynamics to prioritize wildlife conservation

Highly pathogenic avian influenza viruses (HPAIV) have had disastrous, worldwide effects on wild birds and domestic poultry since the emergence of the A/goose/Guangdong/1/1996 (Gs/GD/96) lineage. The currently circulating H5N1 clade 2.3.4.4b has an expanded set of susceptible hosts, including many migratory wild birds, and is associated with higher transmission rates, increased susceptibility among wild bird hosts, and a greater number of wildlife reservoirs. Certain wild bird life-history strategies and behaviors have been suggested to explain avian hosts’ susceptibility and exposure to HPAIV. These biological traits include gregariousness, such as colonial nesting and mixed flock foraging, predation or scavenging on wild birds, and association with aquatic habitats. Variation in host infection responses (e.g., infectability, shedding rates and duration, mortality rate, antibody development) informs the overall infection risk across avian species, yet the specific role of biological traits is often inconsistent and unclear across taxa. Moreover, the interactions and potential compounding effects among these biological traits remain largely unknown. To develop a more holistic understanding of cumulative risk across bird species, we integrate existing information on infection risk factors (i.e., susceptibility, immunological response, and behavioral traits) into a qualitative multivariate analysis. This approach enabled us to examine how infection risk factors relate to biological traits (e.g., phylogeny, physiology, behavior, species range) and to begin disentangling their complex interactions. We quantified and summarized these risk factors across host species and qualitatively ranked species by their viral responses along a proposed HPAIV response continuum, guided by expectations of traits and metrics associated with competence or vulnerability to HPAIV. In doing so, we aimed to better understand how viral responses and biological traits synergistically interact to influence cumulative risk across wild bird species. This work broadly expands on the previous avian influenza literature, which has focused on Anseriformes and Charadriiformes as primary viral reservoirs. We tie our findings to effective disease management responses with links to risk components, including descriptions of potential surveillance strategies applied to research and One Health goals, as well as a fuller understanding of how resources may be better deployed for rapid response when spillovers do inevitably occur. Additionally, we identified numerous areas where vital epidemiological information is lacking to best characterize the spread of these viruses. Ultimately, this improved understanding will help identify and inform disease management needs and decision making.

Wildlife Monographs↗
USGS2025

White‐tailed deer habitat use and implications for chronic wasting disease transmission

Animal space use, activity patterns, and habitat selection—and heterogeneity in these patterns—have important implications for where and when infectious diseases are transmitted. White-tailed deer ( Odocoileus virginianus ) are habitat generalists, with a high degree of heterogeneity in their movement ecology based on sex, age, season, and region. These heterogeneities have important implications for the transmission and management of chronic wasting disease (CWD), which is a deadly prion disease transmitted both directly and indirectly through the environment. As such, favored deer habitats may promote direct interactions between conspecifics or indirect spatial overlap and subsequent environmental transmission. However, little is known about how individual animal space use translates to actual spatial overlap between individuals, leaving uncertainty in how habitat shapes the risk of direct or environmental CWD transmission. In this study, we evaluated seasonal activity patterns, home ranges, and habitat selection for 596 white-tailed deer in southwest Wisconsin, USA, from 2017-2022. We also estimated seasonal encounter distributions—regions where a pair of deer were most likely to encounter each other—for all pairs of deer putatively in different social groups (between-group) in our study, and quantified seasonal variation in the habitat composition of these areas. We found that deer selection for crops, pasture, or grasslands was generally low, relative to forest, but was highest in the post-fawning (summer) and non-breeding (winter) seasons. We observed similar patterns for the habitat composition of encounter distributions, suggesting that crops, pasture, and grasslands may be attractive resources that facilitate between-group transmission. Site fidelity between years was generally high; combined with small female home ranges in the fawning season, this implies that females likely re-use the same small, high-quality fawning habitats from year to year. We found that attraction toward between-group individuals was low during the post-fawning season but high during the breeding (fall) and non-breeding seasons. These results suggest that space use and habitat selection could shape the risk of environmental transmission in the fawning and post-fawning seasons, social selection could favor direct transmission risk in the breeding season, and combined social and habitat selection may shape risk of both direct and environmental transmission during the non-breeding season. We provide a detailed picture of the physiological and social drivers of deer movement through the year, with implications for CWD transmission and management.

Iowa, Wisconsin↗