LE3 .A278 2019

2019

Mallory, Mark

Acadia University

Master of Science

Masters

Biology

Biology

Colonial nesting common eiders (Somateria mollissima) are a culturally significant, broadly-distributed, harvested sea duck. They are particularly vulnerable to a variety of threats (e.g. predation, disease, overharvest, contaminants, commercial fisheries), and some colonies in eastern North America and the Baltic Sea have experienced significant declines over the past few decades. In the Baltic Sea, some population declines have been attributed to low female survival caused by increased predation on the breeding grounds. In eastern Nova Scotia, monitoring has been undertaken at the Eastern Shore Islands Wildlife Management Area for the past four decades, and breeding surveys have indicated a decline in the number of nesting eiders since the 1990s, as well as reduced female survival (0.83 females, 0.92males). I used aerial imagery, habitat mapping and remote infrared cameras to evaluate whether habitat change and altered predation pressure were contributing to these changes in local breeding populations. Results show a reduction in protective vegetative cover at nest sites, up to a 50% decline in the number of females attempting to breed, and a minimum mortality rate of 3% for incubating females. I also observed increased use of artificial nesting shelters and more stable or even increased breeding numbers on islands with shelters. These changes were coupled with increased and widespread exposure to both mammalian and avian predators, and suggest that eiders are responding to both mammalian and avian predation pressure directly (mortality and/or decreased nesting attempts) and indirectly through altered nesting behaviour (site selection).

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https://scholar.acadiau.ca/islandora/object/theses:3217