The mockingbird was selected as the official state bird in 1933.
From the state of Tennessee's website:
"The mockingbird is akin to the brown thrasher and the catbird. It is ashen gray above, with darker, white-edged wings and whitish under parts; its length, inclusive of the long tail, is about 10 inches."
Additionally, the bobwhite quail was designated as the official state game bird in 1987.