Saturday, February 27, 2016

Common Eider

Common Eiders by Jeremiah Trimble

From "A Dictionary of Scientific Bird Names" by Oxford University Press:
Common Eider:  Somateria Mollissima
Greek:  Soma or somatos refers to the body ~ erion means wool
Latin:  Mollissima means very soft

I watched a gregarious and tightly packed raft of North America's largest duck, the Common Eider, from Little Neck in Ipswich the day after Christmas.  I scoped for a belated gift, a King Eider.  All in vain...


My time was well spent, watching the Common Eiders dive in shallow water for mussels, using their wings to aid in their dives. Others were close to shore in shallow water, dipping and dabbling successfully.  The water was clear with an incoming tide, and my vantage point was from River Road.

Blue or Bay mussels live in intertidal areas often at the low tide mark, attached to rocks and other substrates.   I lived on Great Neck in the late 70's and early 80's, and often my morning walk was in the intertidal area near the Ipswich Bay Yacht Club where mussels were attached to the docks, boats, moorings, rocks and pilings.  A nutritionist years ago told me that mussels contain 1/3 more protein than oysters and that these mussels are low in fat and cholesterol. According to Rachel Carson, the Blue or Bay Mussel is a "virtually untapped shellfish resource."
The eiders' predominately mussels diet is low in fat and high in protein.  Eiders feed during the day by diving to the bottom in waters from 9 to 65 feet in depth to take mussels, clams, scallops, sea urchins, starfish.  All of these are swallowed whole and pulverized in the their large, efficient gizzard.

In winter when the days are short, nearly 1/2 of their daytime hours are spent foraging. Rafts move together at the same rate, often the lead ducks dive first, and others do so sequentially.  I observed that, after 20 to 25 minutes of intensive feeding, they moved to deeper waters offshore.  Some rested; others preened.  All were digesting the contents of their gullets.  Every now and then, I get a hankering for those Ipswich clams and think of rafts of wintering eiders savoring the Ipswich mussels!

It's the eiders' layer of fat, the highly effective insulating abilities of their down, and their dense plumage that keep these five pound, icy water ducks warm.

Good birding,
Sue

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