Air and blood

A hummingbird's heart beats 615 times a minute

Flying takes a lot of breathing power, and a bird's body is adapted to give it extra puff. It has an extra large breathing system, which takes up about one fifth of the space in its body. The average mammal's breathing system only takes up about one twentieth. Birds have an extra strong heart to keep this system working.

Mammals’ lungs

People are mammals. Like all mammals, we breathe air down our throat into special breathing sacks in our chest, called lungs. This air contains oxygen, which makes our muscles work. Our blood carries this oxygen around our body. As it is used up, it is converted to a waste gas called carbon dioxide – which we get rid of by breathing out.

Birds’ lungs

Birds also breathe in oxygen and breathe out carbon dioxide. But they have special air sacs as well as lungs, and hollow bones that allow the air to flow around. This means that one bird breath goes further and does more work than one mammal breath. It also means that birds have a constant supply of fresh air in their lungs, giving oxygen more chance to enter the blood supply.

A big heart

Flapping takes lots of energy. Birds need to move the blood quickly around their system to keep their flight muscles working. To do this, they have a relatively bigger and more powerful heart than a mammal’s. Small birds’ hearts beat faster than big birds’. A chicken’s resting heartbeat is 245 beats per minute, a house sparrow’s is 460, and a hummingbird’s is 615. During flight, a small bird’s heartbeat rises above 1,000 beats per minute.