Need ID help please

Photographed this bird here in central Illinois.  A large crop, a male gold finch had just landed in a tree some distance from where I was standing and this bird, which is larger than the finch chased it away.  I am thinking maybe an evening grosbeak?

Thank you for your help.

American goldfinch in  transition to its basic or winter plumage........................Jim

It could be an American Goldfinch in transition, but the fact that you said it was larger and chased the others away argues against that.  I think it could be an Evening Grosbeak in transition.  The dark on its backside is actually its wings.  The latter half of the grosbeak's wings are black.  I also like the stripe above the eye for the grosbeak  The thing that throws me off about the grosbeak id is the bill color.  It should be fading from green-yellow to pale, and in this photo it looks to have a reddish cast.  In a nutshell, I'm not sure.

On further thought...August is the prime breeding time for American Goldfinch.  Goldfinches should not yet be in transition.  So I am leaning toward the Evening Grosbeak, and dispite its color, the heavy beak looks more like a grosbeak beak than a goldfinch's.. 

The head and bill are too small for evening grosbeak. The size of the mint stem that the bird is perched on suggests that this is not a large bird. ....................Jim

Definitely an American Goldfinch.  I don't know about the mid-west, but out here ours are well into transition.  The males are looking particularly scruffy at the moment, though the females are just starting to change.