"The doctors’ conclusion... is that Beckett was attacked by a large bird of prey, probably a great horned owl."

"He likely encroached, unknowingly, on the bird’s nest and was blindsided with such force that he was knocked unconscious. The image of our son alone, face down in the snow, is haunting. We wonder what might have happened if he hadn’t managed to stagger to his feet and find his way home...  Andrew Vitz, the state ornithologist, tells me the Fells is home to raptors, including several types of hawks. But because hawks nest in the late spring and summer, they typically don’t behave aggressively in winter. If they do strike, Vitz says, hawks don’t inflict the sort of damage that was done to Beckett. But great horned owls, which also reside in the Fells, are another matter. They nest in the winter and they’re bigger, more powerful birds, weighing about 4 pounds and capable of flying 40 miles per hour. Great horned owls are notorious for their stealth and strength. They strike without warning — their feathers are adapted to minimize noise during flight — and their long, needle-sharp talons can apply sufficient pressure to snap the spine of their prey. 'The great horned owl is a large, very strong bird, and when it strikes, it’s almost always at the head'..."

From "Something attacked my son while he was sledding in the woods. But what?/My child went sledding alone and emerged from the trees bloody and dazed. He still can’t remember what happened" (Boston Globe).