Mystery Bird?

Recently I glimpsed a bird flying away from my feeder which borders a Connecticut forest. I only saw it from the back. But as it flapped it wings fairly noisily to escape, it flashed  yellow stripes  beneath each wing.  It had  white and brown mottled coloring on its back and wings.  It was bigger than a songbird, but smaller than a turkey vulture; possibly the size of an owl or hawk? Nothing seems to match this description. Any ideas or pictures?