I frequently observe gulls on the Seattle waterfront catching and swallowing whole sea stars, as this gull ultimately did. I remember the first time, years ago, that I ever saw this behavior. I was freaked out, thinking the gull was going to choke and die. At the time, I had no idea how adapted gulls are to this particular food source. This Scientific American article talks about how the two species may have co-evolved, with sea stars even developing color variations in response to gull predation.