Featuring "Birds"

Birds are a group of warm-blooded vertebrates constituting the class Aves, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweight skeleton. Birds live worldwide and range in size from the 5.5 cm (2.2 in) bee hummingbird to the 2.8 m (9 ft 2 in) ostrich. There are about ten thousand living species, more than half of which are passerine, or "perching" birds.

Characteristics

Birds have various characteristics that set them apart from other animals. These include:

• Feathers: All birds have feathers, which are complex structures that are light but strong enough to provide lift for flight. Feathers also provide insulation, and are used in display, camouflage, and signalling.

• Beaks: Birds have beaks, or bills, made of keratin. Beaks vary greatly in size and shape, reflecting the diverse diets and feeding methods of different bird species.

• Eggs: Birds lay hard-shelled eggs, which are incubated outside the body. The colour and pattern of bird eggs vary widely.

• Metabolism: Birds have a high metabolic rate, which supports their ability to fly and maintain a constant body temperature.

• Heart and skeleton: Birds have a four-chambered heart and a strong yet lightweight skeleton, adaptations that support their active lifestyles.

Classification

Birds are classified into two main groups: the Palaeognathae (ratites and tinamous), and the Neognathae (all other birds). The Neognathae are further divided into the Neoaves (all modern birds except fowls and game birds) and the Galloanserae (fowls and game birds).

Evolution

Birds are thought to have evolved from theropod dinosaurs during the Mesozoic Era, around 150 million years ago. The earliest known bird is Archaeopteryx, a transitional form between dinosaurs and modern birds.

Conservation

Many bird species are threatened with extinction due to habitat loss, pollution, and climate change. Conservation efforts are underway to protect these species and their habitats.