Birds are a class of animals that includes tens of thousands of species, making it one of the most successful and classes in the animal kingdom.

They are covered with feathers – a feature that sets them apart from all other modern animals – and their front limbs have become wings that allow most of them to fly in the air.
Nonetheless, some birds’ species whose wings have degenerate lost all ability to fly.
Birds are well adapted to aviation – they have a light beak instead of teeth, hollow bones for weight saving, and a unique system of air sacs and lungs for particularly efficient breathing.