Common Eider Duckling Survival Study

Allen, Brad
Maine Dept of Inland Fisheries and Wildlife
Publication Date: 

The Gulf of Maine is changing, and wildlife species that breed, nest, raise young and winter there have faced considerable
change in recent years. This was no more evident than in 2012 when ocean temperatures rose an incredible two
degrees, setting the wheels in motion for significant changes in complex marine food webs. Common eider populations,
too, must adapt to a significantly altered food web, as numerous studies report widespread losses of the once-abundant
blue mussel populations, the eiders preferred food item. Maine nesting eider populations, while still abundant, have
declined as much as 50% over the last 25 years. Recent analyses indicate that annual production is not sufficient to
offset the annual mortality levels, and this has resulted in a population decline. In previous investigations, we have found
that while adult survival rates for adult males and adult females remain relatively high, changes in recruitment of young
eiders into the population may be a major contributing factor in the population decline. It is believed that extremely low
rates of duckling survival are the greatest limiting factor affecting the population growth and stability of common eiders in
the Gulf of Maine. American common eiders are a USFWS Focal Species, and a high priority of the Sea Duck Joint Venture (SDJV).
This work serves to evaluate a priority management action identified in the draft Common Eider Focal Species Plan, and links
management actions to the draft Atlantic Flyway Gull Management Plan. Improving our understanding of the survival
rates of common eider ducklings has been identified as one of the highest priorities in the recent report to the SDJV.
Specifically, our goal is to evaluate the effectiveness of gull control as a management tool for increasing common eider
duckling survival. For this reason, beginning in the spring of 2016, we began a duckling survival study with U.S. Fish
and Wildlife Service, Biodiversity Research Institute, U.S.G.S. Patuxent Wildlife Research Station, and U.S.D.A. Wildlife
Services.In early May, our field team visited one common eider nesting colony in Casco Bay, Maine. The timing of our visit was
designed to safely capture hen eiders prior to the onset of egg-laying and nesting activities. We used a floating mist net
technique to capture hen eiders paired with mates adjacent to their nesting island. Healthy hen eiders were weighed,
measured, banded, and uniquely marked with plastic nasal discs and an external radio transmitter; we marked a total of
50 hens. We have begun conducting weekly boat-based surveys, using radio telemetry tracking equipment and nasal
disc re-observations in order to locate each individual hen and determine the presence or absence of ducklings. I’ll report
on duckling survival in the near future, so please stay tuned.
-- Brad Allen

Citation Information: 
2016 Research and Management Report