In my home state of CT Common and King Eiders are both very uncommon, although the Common has been on the increase. In Cape Cod, where I do much of my birding, the Common Eider remains a symbol of the windblown birding out there, very Common all over the Cape. The King is less common but a few do winter in a few places. I was lucky to catch up with two females: one in December in Wellfleet Harbor and a returning female in the Cape Cod Canal. I took a bunch of photos of the King along with Commons in the Canal and will post them in this short ID article about identifying a female King Eider vs. a female Atlantic Common.
As I mentioned in my post Bad Blogger-Stay Tuned, I have been very excited to post some of the bird ID articles, as well as book and ipod app reviews and other things that I have written for posting. I wrote this article back in January after visiting the canal and wanted to focus on female eiders for two reasons: 1-The female King is overlooked, while the two other often-seen King plumages (adult male and 1st winter) are much easier to identify. 2-Because they are overlooked, a lot of good records are missed and I hope to help mend that, at least on a small scale.
A few key features in IDing female Eiders:
Those who have seen the Common and King side-by-side before know there is a good difference in coloration. The female Common is a bold rufous, while the King is a buffy tannish, much paler than the Common. The female King’s face is also a lot paler than some other parts of its body, while the Common’s remains similar. There is also a prominent half-circle above the King’s eye as is the pale line that runs from the eye to the base of the neck. Here is a good comparison photo:
Although only 2″ larger, the female Common looks much longer in the field. When comparing the two, the King looks like a Common that has been condensed a bit. In the above photo the King’s back is a lot higher as well a the Common’s head being a lot longer. When looking at an eider flock, the smaller, fatter bird can sometimes stick out a lot but it all depends on how the birds are riding the water, although the Common’s longer neck usually sticks out. This is only a reliable field mark AT TIMES, don’t use it as your main one. Scan carefully.
This a good field mark, much more reliable than #2. The female Common has a gray bill with a small, curved yellow tip, while the King has a striking black bill (at least when next to a Common). The Common’s is also longer and covers the face more.
Just in case your female eiders are flyby’s, it is a similar situation as the bills, the females King’s underwing is Black while the Common is gray. Both species “armpits” are white.
All these features depend on conditions in the field. Two rules to go by: 1-No picture in the field guide replaces field experience and 2-Never ever rely on a single field mark
Please tell me what you thought of this post. It’s my first and this is always a work in progress.