This seems like a Heron or an Egret (which is smaller), one of the 64 known species of freshwater or coastal birds of the Ardeidae family.
Although similar to other bird families (storks, spoonbills, cranes and ibises,) egrets and herons fly differently, with their necks retracted and not outstretched.
Another unique characteristic found only on few birds (parrots and tinamous) is their feathers, known as "powder down".
