Featured: This is the story of how hummingbirds became the ultimate creatures of the air. Hummingbirds live at the limits of what is possible. They have the highest metabolism – with a heart rate of 1,200 beats per minute – of any vertebrate. Their wings beat 50 times a second. They can hover on the spot, and even fly backwards. To our eyes, they are just a blur. But with the aid of high-speed cameras we can slow down their hyperactive lives and look into their secret world.