Female and juvenile Cape May Warblers can be confused with Yellow-rumped Warblers. They both have the distinctive yellow ‘rump’.
There are tell-tale signs that this is a Cape May – there can be a yellow wash to the breast as you can kind of see in the above photo.
This is an adult in ‘basic’ or winter plumage. You can still see the orange ear patch, although it’s faded and smaller.