Do hummingbird moths or something else half the size of a RTH fly with hummers, chase them, and move like them? I'm in SE PA.

I have about 5 RTHs here. Then I have this little thing that acts like a hummer.

Yesterday, a hummer flew across the yard chasing a house finch and something about half the size of the hummer was chasing the hummer. This little fellow has been with the hummers in the back yard.

Today, two hummers passed through the yard chasing each other and the little fellow was right with them. In fact, the little fellow flew into the woods with the hummers. I cannot distinguish any difference in flight between the little fellow and the hummers.

Although I have watched the feeder for about 3 hours over the last couple of days, I did not see the little one feeding and I have not had a closeup view of it.