This is the last Part to this mini-blog......... North Atlantic (S. m. borealis) Common Eiders. The winter months are the time I enjoy the most along the New England coast for winter seabird watching. Winter Alcids are my main focus, but also Waterfowl, especially the large numbers of Common Eiders and scattered small flocks of Harlequin Ducks. Cape Cod and coastal Rhode Island from Provincetown to Point Judith is a very productive span of coastline with many locations that are easily accessible that hold large numbers of wintering birds. MacMillan's Wharf, Race Point, Welfleet Harbor, Cape Cod Canal, Newport, Beavertail Point, Point Judith are just a few very productive areas.
Each winter from December through March, Jen and I make quite a few day trips to the Cape Cod Canal from Bourne to Sagamore. The reason being the massive numbers of Common Eider that spend the day in the Canal feeding and resting. In the morning there are great flights of Eiders heading into one end of the Canal on the Cape Cod Bay end, and also from the Bourne end of the Canal in Buzzards Bay. The great rafts of Eiders simply swim with the tide heading into the Canal and end up concentrating in several areas. In the afternoon, they simply fly out of the Canal in huge numbers and back out into the open water of the Bays. Each side of the Canal has a service road that runs alongside the Canal and simply walk in the directions of the birds. The Eiders are generally sitting right along the shoreline of the Canal...... all you have to do is sit quietly and let all the birds pass by. There are several locations along the Canal that are easy to access from the parking lots.
For me, its a great opportunity to look for King Eiders mixed in with the mass of Common Eiders. King Eiders usually show up later in the season with January usually being the earliest. Mid-February through March is ideal time. My main focus is to find the Atlantic Common Eiders (common New England species seen) northern cousin, the slightly smaller "Borealis" Eider. This species is common in northeast Atlantic Canada and Newfoundland. Usually by mid December, these northern "cousins" begin showing in the waters off Cape Cod, and especially in the Canal. To find them just requires an understanding of the subtle differences in the bill structure and the different plumage coloration and shapes of the green in the jowels areas of the drakes. It also takes a great deal of patience to look through several thousand Eiders that are spread-out all along the Canal.
The bills of the borealis Eider is much smaller and has a shorter pointed or slightly rounded shape (on the drakes) on the frontal process of the bill (aka bill lobes). The common New England drake Eider has a long and larger extended lobe that is well rounded. The green jowels coloration of the borealis Eider is sharply cut-off along its edge near the white cheeks and does not extend to the eye, where the green coloration blends to the white cheeks and extend to the eye. Hen's bills are similar to the drakes but a little shorter and very pointed.
Don't expect to find many borealis Eiders in the large rafts, the most I have found in one morning was 8! I usually find at least 3 or 4, but also have had 7 birds a couple of times. There are probably more in the rafts, but since the raft of Eiders are usually spread-out in both directions in the Canal for a long distance.....it would require a lot of time, walking and searching!
From the Cape Cod Canal- 2022 and early 2023-
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As I mentioned above, you never know what you will find scanning through the rafts....... an intergrade Common Eider (S. m. dresseri x ??)
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And another intergrade Common Eider (S. m. dresseri x S. m. borealis) showing the typical black gular "V" marking. I was thrilled to find this one!-
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Usually on the drive home, if there is time, we always make a quick stop at Beavertail Point. This day I was lucky, found a drake "Borealis" Eider in the raft of Common Eiders-
