It may interest you to know, of all bird species, hummingbirds have the largest known relative heart size. The heart represents 2.4 percent of their body weight. This is quite large for such a tiny bird.  An active hummingbird can have an incredibly fast heart rate. A rate of 1260 beats per minute was measured in a Blue-throated Hummingbird.

In torpid hummingbirds, the heart rate can drop to 50-180 per minute. This is because the sleep of torpid hummingbirds is a sleep that is as deep as death. According to the book, American Ornithology, written by Alexander Wilson in 1832, torpor is described as follows: "No motion of the lungs could be perceived … the eyes were shut, and, when touched by the finger, [the bird] gave no signs of life or motion."