Annual Cycle Phenology and Winter Habitat Selection of White-Winged Scoters in Eastern North America

Dustin Meattey

doi:10.23860/thesis-meattey-dustin-2018

Abstract

Concern over declining populations of several North American sea duck species has led to research addressing how environmental and anthropogenic factors in various stages of the annual cycle affect survival, habitat use, site fidelity, and migratory strategies. Southern New England provides key wintering habitat for White-winged Scoters (Melanitta fusca). This area has also pioneered the development of offshore wind energy in North America. I deployed implanted satellite transmitters in 52 adult female White-winged Scoters captured during the wintering period in southern New England, and on a molting area in the St. Lawrence River estuary in Quebec between 2015 and 2016. I used winter movement data to determine winter arrival and departure dates, total length of stay, home ranges, and site fidelity for scoters wintering in southern New England. Scoters spent over half of the annual cycle on the wintering grounds and demonstrated a high degree of inter-annual site fidelity to composite core-use areas. Sizes of individual 50% core-use home ranges were variable (x̅ = 868 km2; range = 32 to 4,220 km2) and individual 95% utilization distributions ranged widely (x̅ = 4,388 km2; range = 272 to 18,235 km2). More than half of all tagged birds occupied two or more discrete core-use areas that were up to 400 km apart. I combined these home range estimates with biotic and abiotic habitat data to calculate resource selection functions to model predicted relative probability of use for White-winged Scoters throughout the southern New England study area. Scoters selected for areas with lower salinity, lower sea surface temperature, higher chlorophyll-a concentrations, and higher hard-bottom substrate probability. Resource selection function models classified 18,649 km2 (23%) of the study area as high probability of use, which included or immediately bordered ~420 km2 of proposed Wind Energy Area lease blocks. Important habitats and key environmental characteristics identified by this study should be carefully considered when siting and developing future offshore wind energy areas. Understanding full annual cycle movements of long-distance migrants is essential for delineating populations, assessing connectivity, evaluating crossover effects between life stages, and informing management strategies for vulnerable or declining species. In a complementary second study, I used the same 52 satellite-tagged female White-winged Scoters to document annual cycle phenology, delineate migration routes, identify primary areas used during winter, stopover, breeding, and molt, and to assess the strength of migratory connectivity and spatial population structure. Most scoters wintered along the Atlantic coast from Nova

Highlights

Effective management and conservation of any migratory species relies on a thorough understanding of that species’ seasonal distribution and resource use, as well as threats from anthropogenic and other sources
Survival and Transmitter Performance Of the original 22 female White-winged Scoters implanted in Cape Cod Bay during fall 2015, two died within two weeks of transmitter deployment, eight transmitters went offline in presumed live birds either during the first winter or outside the study area during migration or breeding
Of the four female White-winged Scoters implanted in Long Island Sound in March 2016, two died before returning to the study area the following winter and two transmitters went offline in presumed live birds, none of these birds provided a full winter of data for resource selection analyses

Summary

Introduction

Effective management and conservation of any migratory species relies on a thorough understanding of that species’ seasonal distribution and resource use, as well as threats from anthropogenic and other sources. In North America, there is increasing concern over declines in populations of several sea duck species (Sea Duck Joint Venture Management Board 2014, Bowman et al 2015). Reasons for these apparent declines are uncertain, poor habitat conditions and foraging availability on wintering grounds have been linked to significant mortality events (Camphuysen et al 2002), reduced annual survival (Petersen and Douglas 2004), and decreased productivity in subsequent breeding seasons (Oosterhuis and van Dijk 2002). The potential impact of OWEDs on sea duck populations is a recent conservation concern in the United States, on their wintering grounds because numerous other multi-turbine wind energy leases have been issued for offshore areas in New England and mid-Atlantic states (Manwell et al 2002, Breton and Moe 2009, Musial and Ram 2010). The strength of connectivity (i.e., the extent to which individuals from discrete breeding or non-breeding areas remain in sympatry after migration) can have critical implications for conservation strategies that consider the full annual cycle of a species

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