Experts are telling Chicago residents to beware of the birds.

The fiercely territorial behavior of red-winged blackbirds is being blamed on several recent dive-bomb attacks. The birds peck at unsuspecting bicyclists and pedestrians and swipe their hair.

Just ask Holly Grosso. The businesswoman says she was pecked in the head. She calls the incident “so bizarre.”

Field Museum ornithologist Doug Stotz says the birds favor parks and vacant lots near ponds and Lake Michigan.

Relief may come in late July, after their nesting season ends.