After looking at it, I'm going to have to go with starling, personally.
Search under google images for 'gray catbird' and 'starling' and you will see there is a large difference is appearance.
Here is the list for the Starling:
from: USGS.com
Identification Tips:
Length: 6 inches
Pointed bill-yellow for most of year, dark in fall
Black plumage with green and purple iridescence
White spots scattered about head and body-largest in fall
Dark wings and tail
Pointed wings
Short tail
Juvenile gray-brown with faint streaking below
Very common-frequently seen in large flocks
Here is the list for the Gray Catbird:
From the same source, different page:
Length: 7.75 inches
Slender bill
Dark gray plumage (yes)
Dark eye (yes)
Chestnut undertail coverts (yes)
Crown and tail black (crown black, yes)
Black legs
Sexes similar
Often found in dense vegetation (this picture, seems yes)
Distinctive call like cat's meow