Hummingbirds have massive hearts to power their hovering flight

Birds that hover in front of flowers have huge hearts to power their energy-intensive flight, and even birds that glide effortlessly need fairly big hearts to keep it up

How well a bird flies depends on how big its heart is. The best flyers, like hummingbirds that dexterously hover in front of flowers, have the largest hearts. But unexpectedly, soaring and gliding turns out to be almost as much work as flapping wings.

Previous research had suggested this, because sustained flight requires more aerobic power, which depends on heart size. The heart is like a carburetor pumping fuel into an engine: the bigger the heart, the more blood a bird can pump to its flight muscles.

Hummingbirds have the biggest hearts for their body size, about three per cent of their mass. In contrast, a pelican’s heart is just 0.8 per cent of its mass.

When a hummingbird hovers in place, air doesn’t move past its wings to generate the lift needed to keep it aloft. Instead, it beats its wings in a figure-of-eight pattern