Day 11.272: Confusing fall warblers

My main bird identification book is Peterson's Birds of Eastern and Central North America. It's generally excellent, but I always dread finding myself in the section titled "Confusing fall warblers". Not all the birds in the section are even warblers, but that just adds to the confusion.  Nevertheless in attempting to identify this small fly-catching bird we saw at the weekend, I ended up in those pages.

Not surprisingly, I'm still confused.