What is this? My first inclination based upon length and slimness was a warbler but it really doesn’t match anything in my bird book. When I looked at it some more, it seemed to be closest to a female goldfinch but it isn’t autumn yet. And it does appear too large to be a finch. Can someone positively identify it?
I saw 4 of these and they seemed to coexist yet later one was aggressive toward another and chased it off.