When I lived in Chicago and banded birds along the shore of Lake Michigan, one HIGHLIGHT for me was banding multiple CONWs each spring. They tend to be
late migrants in the Chicago area, and Memorial Day always seemed to be the peak time. The species is often misidentified (especially in the fall), but in the hand the birds are really different
from the similarly-plumaged Mournings; most importantly, the eye ring is (structurally)
a raised ring of feathers that surrounds the bird's eye. There's also the tail
length and length of the undertail coverts, but this raised ring of feathers is pretty obvious when one has the critter in one's hand.
This bird is pretty clearly a CONW . . . nice find.