Dark Eyed Junco harassing an American Robin (1 Viewer)

Today I observed a Dark Eyed Junco harassing an American Robin. It would chase it from tree to tree and when in flight get very close to the robin chasing it.

Why? I'd expect that kind of behavior from a nesting bird but the Dark Eyed Junco's vacate my area (Eastern Massachusetts, USA) and go north to do their nesting. I never see them in the summer. But this year there are still at least 50 in my yard which have not left yet.

Might they be staying this year?

Probably just feeling its oats as testosterone levels build up prior to migration to the breeding grounds.

I have those in my backyard, never seen them fight. It's probably as the above stated, in spring hormones in birds (like all animals) turn on high and outlandish behaviors can happen. I saw a robin on my lawn and it let me walk extremely close to it for some pics, they are fearless right now lol