The King Eider is a large sea duck from the New England area and high arctic. Within their range, they can be found in very large flocks with other ducks and waterfowl.
When King Eiders venture inland, they are almost always never adults in breeding or transitioning plumage, meaning that they won't have that striking, silky black and white body with a beautiful blue head and orange forehead knob.
A young male King Eider will be overall chocolatey brown with darker brown mottling. Some will have a partially orange bill and a small knob, but can also have a solid black or dark gray bill with very little trace of the forehead knob. Another thing to look for is the very interestingly patterned belly. It is a gray and brown scaled pattern on the lower breast and the rest of the belly is covered with fine brown barring. The upper breast is usually white with some scattered scaling.
In flight, a young male King Eider will have dark underwings with a white or light gray triangle from the axilleries somewhat bleeding over into the secondary underwing coverts. On the upperwing, there is no brightly colored speculum, but there is a white border on the inner secondaries stopping at the trailing edge and secondary coverts.
King Eiders are sea ducks, and have large and strong feet and yellow legs that are a dull yellowish-orange coloration for paddling through the harsh, winter, Atlantic surf.
King Eiders are fairly large, about half the size of a Canada Goose. They are very bulky bodied with extremely rear placed legs. They are not well suited for walking on land, similar to many other water birds.
BEST MONTH TO FIND ONE - November - February
WHERE TO FIND ONE - Overall Lake Michigan shoreline. Waters off beaches, harbors, piers are all great places to look. The Chicago River, Calumet River and Little Calumet River turning basins are great places to look as the water in the turning basins usually stays open even when the rest of the rivers freeze over.
IDEAL CONDITIONS TO FIND ONE - Strong easterly winds particularly from the New England region in the range of time specified. November is always the best month to potentially find one, but February also has multiple records.
SIDE NOTE - The Common Eider is another Atlantic sea duck closely related to the King Eider, and multiple have found their way to the Great Lakes region in the past. Common Eiders are exponentially rarer though. You would likely find one in the nonbreeding season, so the plumage you might find one in would look similar to a King Eider. Common Eiders are a bit larger, sit lower in the water, more like a Common Loon, are darker brown and more finely barred overall, and have a longer, solid black bill, closer in appearance to the bill of a White-winged scoter.
My own iNat observation - https://www.inaturalist.org/observations/67104142
eBird link for more photos - https://ebird.org/species/kineid
Also sorry for the delay on this one, I was just super busy yesterday with the festivities all happening at once, and I'll be doing one a day from now on!