Maybe you remember the adult intermediate-morph Rough-legged Hawk photos that Alex posted earlier this month? There is currently a thread in the North American Birders Forum discussing that bird, with raptor experts Vic Berardi and Jerry Liguori both chiming in on the age/sex/morph of the bird.
Here’s what Liguori had to say about Alex’s bird-
Since there is a cline from light to dark in Rough-legged plumages (and several other buteos), labeling every bird specifically is sometimes a matter of opinion. There are no absolute parameters that define light, dark, and intermediate, although most Rough-leggeds are clearly light or dark morph. The bird is an adult male, they are the only age/sex that shows this extensive mottling throughout the underside (the defined dark tail tip and terminal band on the remiges are clear adult traits as well). Because the bird has a light morph tail pattern (as it appears) and white on the belly, lower chest, and underwing coverts, I call birds like this “heavily marked light morphs”. To me, an intermediate morph will appear more like a dark morph but has a paler chest and possibly white on the chest that separates a “bib” (and the tail has very limited white at the base). But this bird leans toward intermediate morph and calling it one wouldn’t necessarily be incorrect because where one draws the line is subjective.
Discussion of the State College Bird >> NA Birder’s Forum
Intermediate Rough-legged Hawk Discussion >> Illinois Birder’s Forum