What are the essential characteristics of a bird?

Birds are vertebrates with the following essential characteristics:

1. Feathers: The unique feathers of birds are one of their most distinctive features. They not only help birds stay warm and fly, but also provide color concealment and ostentation.

2. Tympanic ears: Birds have a very sensitive hearing system, the key part of which is the tympanic ear. This ear structure allows birds to hear high-frequency sounds, helping them sense their surroundings and find prey.

3. Beak: The beak of birds is a tool used for multiple functions such as catching food, cutting, and crushing. Different species of birds have different beak shapes, sizes and angles to suit their different lifestyles.

4. Hollow bones: There are many hollow parts in the bones of birds, which help reduce the weight of the body, making it easier for the bird to fly.

5. Forelimbs transformed into wings: The forelimbs of birds have been transformed into wings, which is the key to their ability to fly. In addition, birds also have strong chest muscles and fine flight skills, allowing them to fly freely in the air.

6. Internal organs: Like other animals, birds also have internal organs, including heart, liver, lungs, etc. But unlike mammals, the heart of birds is composed of four atria and two ventricles, which help to effectively separate oxygen and carbon dioxide.

In short, the above characteristics are important indicators for determining whether a creature is a bird, and each characteristic has its own characteristics, which together constitute the unique charm of birds.

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