Mystery Bird

Today me and my friend went to a nature center in hartsdale. We were looking for owls. When we got to the lake it looked like the path because on top of the ice their was snow. The only reason we knew it was a pond was because it had a stream running through it. When we left the pond to go back I saw a bird that had a white belly and its wingspan was probably from my feet up to my chest! I assumed that it was an owl.