Been meaning to speak to your cat about all the complaining she’s been doing lately? What? You don’t have a cat? Well then it’s probably a Gray Catbird you’ve been hearing. This species is named for its cat-like call. There are a few birds who’s call is easy to remember, and this is one. Gray catbirds are related to Northern Mockingbirds and Brown Thrashers and like them, will mimic the sounds of other birds.  This bird is actually able to make two sounds at the same time. The alarm call resembles the quiet calls of a mallard. 
Gray catbirds are plain lead gray almost all over. The top of the head is darker which make it look as if it has on a cap. The slim bill, the eyes, and the legs and feet are also blackish. Males and females cannot be distinguished by their looks; different behaviors in the breeding season are usually the only clues to the observer. 
This year, 2016, we’ve seen more Catbirds than usual for some reason. They’re everywhere: outside all the windows, at the suet feeders and in the trees.
Their breeding habitat is semi-open areas with dense, low growth; they are also found in urban, suburban, and rural habitats. In the winter months they actually seem to associate with humans even more. These birds mainly forage on the ground in leaf litter, but also in shrubs and trees. They mainly eat arthropods and berries.
References and Additional Information
 Wikipedia: Gray Catbird
 The Sibley Guide to Birds, second edition – David Allen Sibley
 Cornell – All About Birds: Gray Catbird
 Cornell – All About Birds: Gray Catbird – sound
 The Breeding Bird Atlas of Georgia – UGA Press: Schneider, Beaton, Keyes and Klaus, Eds.