How does a five-week-old hummingbird know the difference between a deadly hawk and a harmless vulture? The knowledge could be innate. Or it could be the result of careful observation. Hummingbirds are curious and astute observers. Backyard hummers quickly learn to recognize individual humans and approach people who feed them—even if they are not carrying food. (Sometimes they’ll hover at windows to attract a particular person to come out and refill an empty feeder.)
