Remigial Molt in the Annual Cycle of Sea Ducks

Barrow’s Goldeneye Spatial Ecology: Satellite Telemetry Studies of Migratory Connectivity, Population Structure, Habitat Use, and Migration Strategies

In this ongoing project, we are evaluating movements and habitat use of Barrow’s Goldeneyes throughout their Pacific Range. The work is designed to provide insights into the degree of demographic independence of subpopulations, accounting for distributions throughout the annual cycle, which is critical for delineation of meaningful management units for migratory animals.  We also have identified important habitats and heretofore unknown important sites (e.g., Hogan et al. 2011) for the species.  This work also is one of very few studies that have evaluated movements of juveniles throughout the annual cycle, which is often overlooked in considerations of population delineation.  More detailed description of the work and current results are presented on our web site.

CWE Personnel: Sean Boyd, Dan Esler, Jenn Barrett

Collaborators: Environment Canada, U.S. Fish and Wildlife Service, Ducks Unlimited Canada, U.S. Geological Survey, Alaska Department of Fish and Game, B.C. Ministry of Forest, Lands, and Natural Resources, Pacific Wildlife Foundation, Alberta Conservation Association

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Evaluating Factors Affecting Site Selection and Differential Migration of Wintering Surf Scoters: Continental-scale Variation in Demography and Foraging Conditions

Surf scoters exhibit differential migration to wintering sites; i.e., sex and age classes are differentially distributed by latitude, with proportions of adult males higher at northern wintering areas and proportions of females and juveniles higher at southern sites.  We conducted a Pacific-wide study to evaluate factors related to observed patterns, from Baja California, Mexico, through the range core in coastal British Columbia, to southeast Alaska. We measured foraging effort, body mass variation, and survival of all age and sex classes.  Foraging conditions were best in Alaska and declined with decreasing latitude, based on measures of foraging effort of radio-marked individuals.  On average, scoters in Mexico foraged more than twice as much as those in Alaska, and foraging activity in Mexico extended into nocturnal periods, which was rarely observed in British Columbia or Alaska.  Conversely, average survival was lowest in Alaska and increased with decreasing latitude, suggesting that individuals trade-off foraging conditions against survival probability when choosing wintering sites.  However, the nature of that trade-off varied by age and sex class.  Foraging effort by juvenile females in Alaska was considerably higher than average.  Also, survival variation by latitude was driven largely by juvenile cohorts, as adult male survival was similar across sites.  We also found evidence that body mass influenced survival, and speculate that choice of wintering sites at a continental scale reflects trade-offs among latitude-specific and individual conditions that co-vary with age and sex class, leading to observed differential migration.

CWE Personnel: Dan Esler, Sean Boyd, Rian Dickson, Corey VanStratt, Brian Uher-Koch, Tyler Lewis, Molly Kirk, Sam Iverson, Deb Lacroix

Collaborators: U.S. Fish and Wildlife Service, Environment Canada, U.S. Geological Survey, U.S. Forest Service, Ducks Unlimited Canada,  Washington Department of Fish and Wildlife, Centro de Investigación Científica y de Educación Superior de Ensenada, B.C. Ministry of Forest, Lands, and Natural Resources

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Anthropogenic Influences on Sea Duck Habitat Function and Use

We have examined a number of anthropogenic changes to marine habitats, and subsequent effects on sea duck habitat use, demography (survival and dispersal), energetics and physiology, and behavior.

Shellfish Aquaculture—Clam and oyster aquaculture is a common and growing industry in coastal British Columbia and Washington, occurring in habitats that broadly overlap those used by wintering sea ducks.  We conducted a comprehensive research program addressing interactions between scoters and several types of shellfish aquaculture.  To address this issue, we studied processes by which scoters choose foraging patches, the attributes of habitat patches that influence scoter foraging decisions, the spatial scale over which scoters forage, the effects of scoter foraging on shellfish resources, the effects of variation in prey densities and types on scoter foraging, movements, and distribution, and the population-level demographic consequences of these interactions.  We found that, in some cases, shellfish aquaculture had strong positive effects on habitat quality and, in other instances, consequences were neutral.  Given the current types and intensity of shellfish aquaculture, we concluded that there was no deterioration of habitat quality for wintering sea ducks.

CWE Personnel: Dan Esler, Sean Boyd, Tyler Lewis, Molly Kirk, Sam Iverson, Deb Lacroix, Rian Dickson, Corey VanStratt, Brian Uher-Koch, Eric Anderson, Ramūnas Žydelis

Collaborators: Environment Canada, U.S. Fish and Wildlife Service, Ducks Unlimited Canada, Washington Department of Fish and Wildlife, B.C. Ministry of Forest, Lands, and Natural Resources

Exxon Valdez Oil Spill—Sea ducks suffered significant mortality in the weeks to months after the 1989 Exxon Valdez spill.  We have been conducting studies of longer-term, chronic effects of the spill on harlequin duck and Barrow’s goldeneye populations since 1995.  Based on spatially-explicit population models for harlequin ducks, we estimated that full population recovery required 2.5 decades – much longer than conventional assumptions about the duration of oil spill effects on wildlife populations.  These models were built from detailed demographic data describing spatial variation in survival and the degree of site fidelity/movements.  We also determined that sea ducks were exposed to residual oil much longer than anticipated – over 20 years in the case of harlequin ducks.  These findings provide an unprecedented perspective on oil spill effects on wildlife, and are being used as part of risk assessments and management plans for oil transportation and chronic pollution throughout the world. 

CWE Personnel: Dan Esler, Sam Iverson, Rian Dickson

Collaborators: U.S. Geological Survey, U.S. Fish and Wildlife Service, Pacific Wildlife Foundation, Alaska Sea Life Center

Offshore Wind Farms—Offshore wind power is an increasingly attractive energy source. Currently there are no active offshore wind farms in North America; however, there are numerous proposals under consideration, including a major project in British Columbia. Given the successful and growing use of marine wind farms in Europe, offshore wind energy development on this continent is widely expected to increase in the coming years and decades. Therefore, it is critical to evaluate effects of offshore wind farms on marine birds, providing clear recommendations to the industry and conservation agencies about how to minimize effects on wildlife. We conducted a research program to evaluate the habitat use and function of an area proposed for wind farm development in Hecate Strait, British Columbia.  Using a number of physiologic, energetic, and trophic endpoints, we contrasted habitat value in the proposed wind farm area with both local and regional control sites. We found that habitat within the wind farm footprint did not have different value from the remainder (96%) of the local area used by sea ducks.  We also found that sea ducks in Hecate Strait had very different attributes than those in other wintering areas, reflecting plasticity in response to habitat variation.  Overall, we conclude that population level effects of displacement following wind farm construction are unlikely, and we have a number of pre-construction metrics to serve as a baseline to evaluate potential effects.

CWE Personnel: Dan Esler, Sean Boyd, Eric Palm, Eric Anderson

Collaborators: Environment Canada, U.S. Fish and Wildlife Service, Nai Kun Wind Energy Ltd., Natural Resources Canada

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Spatio-temporal Aspects of Surf Scoter Spring Migration: Continental-scale Influences, including the Role of Herring Spawn

As part of a collaborative program marking Surf Scoters with satellite transmitters throughout their Pacific wintering range (see below), we evaluated strategies of spring migration along the Pacific coast, specifically the habitat attributes that were related to timing of migration and location of stopovers.  We found that phenology of departure from wintering areas was adjusted to allow synchrony at later migration stages; i.e., spring migration was initiated earlier at more southern wintering sites.  We also found that both timing and stopover habitat use were closely linked with timing and location of herring spawn events, supporting the idea that scoters strategically modulate their migration to match a “silver wave” of herring spawn availability, likely to help fuel both migration and subsequent reproductive activities. 

CWE Personnel: Erika Lok, Dan Esler, Sean Boyd

Collaborators: Environment Canada, U.S. Geological Survey, Washington Department of Fish and Wildlife, U.S. Fish and Wildlife Service, Centro de Investigación Científica y de Educación Superior de Ensenada

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Migratory Connectivity and Population Delineation of Pacific Surf Scoters

Based on a large collaborative effort to mark surf scoters with satellite transmitters throughout their Pacific wintering range (Baja California, Mexico; San Francisco Bay, California; Puget Sound, Washington; Strait of Georgia, British Columbia; and Southeast Alaska), we are evaluating the degree to which subpopulations can be identified and managed as discrete conservation units.  We found that birds from all wintering areas were admixed at low densities across a broad swath of boreal forest, representing the entirety of the western breeding range.  Also, remigial molt sites of marked individuals were spread throughout the known molting range from the arctic coast of Alaska and Canada through Puget Sound.  Despite a lack of migratory connectivity among annual cycle stages, we found a high degree of site fidelity at each stage.  This finding suggests that local factors that influence scoters at a given stage could (1) have effects that are transmitted and diluted throughout the western North American population, and (2) could have specific effects on numbers or performance of individuals that routinely use that site.

CWE Personnel: Dan Esler, Sean Boyd

Collaborators: Environment Canada, U.S. Geological Survey, Washington Department of Fish and Wildlife, U.S. Fish and Wildlife Service, Centro de Investigación Científica y de Educación Superior de Ensenada

Cross-seasonal Influences on Waterfowl Reproduction: Spatial and Temporal Links Across the Annual Cycle

In migratory birds, different stages of the annual cycle are spatially discrete.  However, that spatio-temporal separation can not be assumed to indicate that habitat conditions or other factors that influence individuals in one stage do not have carry-over effects into subsequent stages.  In fact, there is a growing appreciation for cross-seasonal influences on demographic attributes such as survival or reproductive performance.  We have conducted a number of studies to evaluate the roles of winter and migration habitats for nutrient acquisition for subsequent investment in reproduction.  We have discovered a number of different strategies that shed new light on cross-seasonal energetics.

Harlequin Duck Nutrient Acquisition and Allocation—We tracked body mass variation of both male and female harlequin ducks from late winter through spring staging in coastal habitats and during the nesting period on inland breeding streams.  We found that both sexes achieved optimal body mass prior to migration, irrespective of prey type (herring spawn versus benthic invertebrates); given high prey availability, they could have attained higher mass, but presumably did not due to associated costs.  While on breeding streams, males invested stored reserves in vigilance behaviour whereas females maintained mass and foraging heavily on stream invertebrates, which were shown by stable isotope analyses to be the source of egg nutrients.  Females saved their stored capital for later investment in incubation and brood-rearing.

CWE Personnel: Jeanine Bond, Dan Esler, Ron Ydenberg, Sunny LeBourdais

Collaborators: BC Hydro Bridge Coastal Fish and Wildlife Restoration Program, Whispering Pines/Clinton Indian Band

Greater Scaup Reproductive Energetics—We studied body composition variation in relation to timing of, and investment in, egg formation on the Yukon-Kuskokwim Delta, Alaska.  We found that female greater scaup build reserves on breeding areas and must attain a lipid threshold prior to initiation of rapid follicle growth.  However, those reserves are not invested into egg production, but instead are saved for incubation, allowing higher incubation constancy and subsequently lower nest failure.  This pattern of nutrient acquisition and allocation has not been previously described, and provides a unique view on the capital-to-income-breeding continuum.

CWE Personnel: Kristen Gorman, Dan Esler, Tony Williams

Collaborators: U.S. Geological Survey, U.S. Fish and Wildlife Service

Surf Scoter Spring Migration Energetics—As described above, surf scoters migrating along the Pacific coast during spring are closely affiliated with herring spawn events.  We examined body mass and stable isotope variation of surf scoters from Puget Sound/Strait of Georgia in Washington/British Columbia through the terminus of their coastal migration at the northern extreme of southeast Alaska.  Despite access to abundant food, and isotopic confirmation that herring spawn was an important component of their diet at all latitudes, body mass was stable throughout most of migration, increasing markedly at the final staging sites prior to inland movements.  These data indicate strategic and optimized adjustment of body mass relative to current and future costs and benefits.

CWE Personnel: Eric Anderson, Dan Esler, Erika Lok

Collaborators: Environment Canada, U.S. Geological Survey, Washington Department of Fish and Wildlife, U.S. Fish and Wildlife Service, Centro de Investigación Científica y de Educación Superior de Ensenada

Remigial Molt in the Annual Cycle of Sea Ducks

The wing molt phase of the waterfowl annual cycle is poorly studied, particularly for sea ducks.  Therefore, it is unclear whether this stage could be an energetic or demographic bottleneck with important effects on overall population dynamics.  We have studied remigial molt of several sea ducks (harlequin ducks, Barrow’s goldeneyes, surf scoters, and white-winged scoters), which have very different molt strategies and habitats, to determine whether there are generalities that can be applied across the tribe with respect to the effect of molt on population change.  We found that survival rates during molt were very high for all species.  Also, we found no evidence of nutritional or energetic constraints, based on stable body masses combined with relatively low foraging effort.  We conclude that selection of molting habitats that offer both low predation risk and high abundance and quality of prey is a critical component of sea duck molt strategies.  We also found that habitats that met these criteria varied considerable by species, and influenced their migration cycles and movements.

CWE Personnel: Dan Esler, Rian Dickson, Danica Hogan, Brian Uher-Koch, Eric Anderson, Jenn Barrett

Collaborators: Environment Canada, U.S. Fish and Wildlife Service, U.S. Geological Survey, Washington Department of Fish and Wildlife, Ducks Unlimited Canada, U.S. Forest Service, Alberta Conservation Association, NAWMP

Habitat Use of Sea Ducks in Southeast Alaska

We are conducting regional scale analyses of variation in sea duck occurrence, densities, and diversity in relation to habitat characteristics throughout southeast Alaska.  Sea duck data are derived from aerial surveys conducted by the U.S. Fish and Wildlife Service, which we combine with ShoreZone and other habitat data, using a variety of complex statistical modeling approaches.  The intent of this work is to both identify hotspots of abundance and diversity, and also to generate underlying explanations for why sea ducks occur where they do.  The results from this work, which allow inference at a much larger spatial scale than most habitat association projects, will have important implications for management of habitats and populations.

CWE Personnel: Dan Esler, Dora Gunn, Jenn Barrett

Collaborators: U.S. Fish and Wildlife Service, U.S. Geological Survey, U.S. Forest Service