Kodi and I kicked up two flocks of (common) grackles in the last week or so. Both times and places we were walking a woodland trail not far from water. The rowdy bunch of 50 or so blackbirds were feeding on the ground, tossing leaves in search of seeds, insects, acorns. On our approach they flew up into surrounding trees with great fanfare, squeaking and whistling as they departed the path.
A check of the local bird listserve showed that others have seen much bigger blackbird flocks this week (comprised of mostly grackles along with other blackbirds) of 1,000 birds or more. The gregarious grackles are heading south, picking off whatever foods they can find on the way. The inside of their mouth has raspy parts that help them score and then crack open acorns. The woods that Kodi and I walked were full of oak trees.
The big blackbird flocks are hard to miss -- often seem as long, flowing waves of black birds in the late afternoon. The biggest birds with long tails in the flock are the grackles. Red-winged blackbirds and brown-headed cowbirds are typically mixed in. Watch for the birds in your neighborhood. You might hear them first.