Fascinating Biology and Anatomy of Birds

Key Characteristics of Birds

Birds are terrestrial vertebrates with feathered bodies. They are descended from reptiles, but they are considered to be more evolved as they have a more developed nervous system. Some of their main characteristics are the following:

• They have a fusiform or spindle-shaped body which is covered by feathers, except the legs which are covered by scales.
• Two of their limbs are wings, which in the majority of cases allow them to fly.
• They have a beak, but no teeth.
• They have a highly developed sense of sight.
• They are homeotherm or warm-blooded animals, which means that their internal temperature stays at around 42 ºC regardless of the temperature around them.

The Body of Birds

The body of birds has a very characteristic shape and structures, which means that we can distinguish them easily from other vertebrates. Some of the most characteristic elements of their anatomy are the following:

• Eyes: They are highly developed and protected by eyelids.
• Auditory meatus: Located on either side of their head.
• Nostrils: Two openings on their beak.
• Beak: A hard structure that constitutes the jaw of birds. They can be of different shapes, depending on the bird's feeding habits. They have no teeth.
• Skeleton: Formed of hollow bones which the air flows through. This characteristic makes them light and facilitates their breathing, as the hollows of their bones, called air sacs, are connected to their lungs.
• Lungs: They are small and are connected to the air sacs.
• Limbs: They have four, two legs and two wings.
• Feathers: These are structures that cover the bird's body. They enable them to fly and to keep a constant body temperature in relation to the environment temperature. Long, flat feathers are called contour feathers, and small, fluffy feathers are called down feathers.
• Cloaca: This is the end of the digestive, urinary and reproductive tracts.

Feeding Habits and Beak Adaptations

Birds' feeding habits vary greatly from one species to another. There are carnivorous birds and others that eat fruit, grain or insects. The feeding habits of each bird species determine the shape of their beak. For example, pelicans have a long, narrow beak which allows them to catch the fish that swim underwater easily. Eagles, however, have a hook-shaped beak so that they can tear the meat of their prey.

Reproduction and Life Cycle

In bird reproduction, fertilisation is internal. The female deposits the eggs where the embryos develop in a nest and incubates them to keep them warm until the young are born.