large grey bird, southwester Indiana

by Rachel
(Plainville, Indiana)

I heard a commotion in a nearby tree, saw many birds that had come to sleep in it, flying out of the tree, as a large, light gray and darker gray bird flew out with its wings tucked. The darker color was not truly dark grey, it was just darker than the lighter grey color. It did not flap its wings once that I saw and landed in a tree about 150 yard away. Upon landing it disturbed those birds and they flee away also. What kind of bird could this be? It was large, at least 12-18" in length and since I did not see its wings open I can't determine wingspan. Did not appear to have a shortened beak. I haven't ever seen a bird this size or color here before. Thank you for all your help. Located 20 miles east and slightly north of Vincennes Indiana. 11/2/15