How prolific are Goldens in WI? I don't know that I've ever seen one before but I think I've seen 3 in the last month or so.
They're not. We get a few (less than 20) that winter in WI along the Mississippi river in the SW corner of the state. I have a few friends that are actually part of the group that's been working to trap a few of those birds for the past few winters. They're attaching backpack-mounted GPS units to the birds and releasing them. They can then track the birds for a few years and monitor their movements.
To the best of my knowledge, their aren't any breeding pairs that stay in WI. While they're here in the winter they do actually do some "mock" nest-building; probably as part of pairing. But then they all leave in the spring to nest up in Canada and the western US.
Quite often though, immature bald eagles are mistakenly ID'ed as goldens. Bald eagles don't get their white head and tail feathers until they're 3-4 years old. Could that be what you've been seeing? They can be tough to tell apart, even for someone who knows what to look for. Actually, we have loads of TV's (turkey vultures) in WI, and they're often mistaken for eagles too.
When it comes to bald vs.golden eagle ID, things to watch for are "where", wing dihedral, tail shape, wing chord, and plumage color. Immature goldens are dead giveaways with the white markings on their wings and tails. Adult birds are basically all dark (like immature balds and TV's). TV's have a pronounced dihedral, and "rock" a lot in flight (and as they rock they may display silvery undersides to their wings). Goldens generally don't fly with dihedral, but whether they do or not, the don't "rock".
Immature bald's, depending on their age, show varying amounts of sparse white "speckling", and may even appear golden. Golden's are generally just plain dark, and the immature birds have white in specific patches on the wings and tail. Golden eagles have a much longer tail and shorter head, proportionately, than a bald. The tail of a golden is about 3x the length of the head. Balds have massive heads, and appear to have almost as long of a head as they do tail. Bald eagles have a uniform "plank-like" chord. Golden's have an obvious "indent" where the wings meet the body (like buteos). Golden's often look like overgrown, dark, hawks, while bald's never do...
Golden's aren't that fond of flat ground, and really prefer to use ridges for lift. That usually keeps them along the Mississippi. Bald's soar with no dihedral, or eve with slightly drooping wingtips. Golden's usually have dihedral (not as much as a TV though).
