Dark gray birds with a black strip on the crown, what kind are they?

Where do you live?

You don’t give us much to work with…

Cat bird?

Richmond Virginia

By small, do you mean bigger or smaller than a robin, the standard by which you estimate other birds?

Catbird fits the description but he doesn’t travel in packs and he vocalizes loudly and a lot, imitating other bird calls and meowing (hence the name.)

Is there any flash of white on the birds. Check out the small common ones that travel in groups. Chickadees, tufted titmice, juncos…and the phoebes who hang around with one partner.

Carolina and Black-capped chickadee; http://www.allaboutbirds.org/guide/Carolina_Chickadee/id
Titmouse: http://www.allaboutbirds.org/guide/tufted_titmouse/id
Junco; http://www.allaboutbirds.org/guide/Dark-eyed_Junco/sounds

Check out Mockingbirds (also solitary), brownheaded cowbird, Eastern Kingbird, ...they are biggish birds and again, do not hang out with the crowd.

A sparrow of one sort or another?