Entomology, Ornithology & Herpetology: Current Research
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A brief note on the biology of birds

Greg Dingle^{* *}Correspondence: Greg Dingle, Department of Ornithology, Lusophone University, Luanda, Angola, Email:

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Description

Birds are warm blooded flying vertebrates with more than 10,400 species belonging to the class Aves. They have two eyes, a four chambered heart like humans, and front legs modified into feathered wings. Birds use their front legs to fly and their back legs to rest or perch. Birds lay hard shelled eggs that need warm conditions to hatch.

Even with such a large number of species, there are about 1,000 extinct species of birds that have been recovered from fossils. With such a wide variety of species, all birds produce a single celled egg, incubate, hatch, and then join the group of adult birds. Some birds even migrate during their life cycle.

Life cycle of a bird

The egg–stage 1: All birds begin life in an egg; mostly white, yellow, hard-shelled covering growing bird embryo. The number of eggs laid and the size of the eggs vary from species to species. Some birds lay one egg, while other birds lay more than one egg. A bird called a partridge is known to lay about 20 eggs. The eggs are incubated by one of the parent birds so that the embryo develops into a chick. A hard bony structure called egg tooth forms in the young bird's beak. To hatch, the young bird uses the egg tooth to break through the egg shell.

The hatching–stage 2: After the bird hatches from the egg, the newly hatched bird is called a hatchling. A hatchling is covered with soft features and cannot fly at this stage. Due to its defenseless nature, a hatchling becomes prey for many large predators. They need extreme parental supervision to develop and grow at this stage. When a young grows up and is fed by the parents in the nest, it is called a chick.

The nestling–stage 3: At this stage the bird tries to fly and shows certain flight characteristics. When a chick develops its flying assistances and is ready to take its first flight, the bird is referred to as a hatchling.

The fledgling–stage 4: During this stage, a chick has fully developed feathers and strong muscular wings. Despite all these qualities, the chicks are still in the care of their parents for some time. At this stage, the bird flies out of the nest, but not long distances. The time period of this stage in birds varies from stage to another stage.

The juvenile–stage 5: Juvenile birds leave the nest and can fly independently. At this stage the young bird is going through its first plumage and looks more like an adult bird. A plumage is the layer of feathers that covers a bird's exoskeleton. Young birds cannot reproduce at this stage. The plumage is soft at this stage and is replaced after the mounting stages.

The sub adult–stage 6: At this point, the young birds are not yet fully developed because they do not have adult plumage. At this point in time, young birds are not yet sexually mature. Again, this varies depending on the type of bird species. Some bird species become sexually mature at this stage, while others do not.

The adult–stage 7: The adult bird has definitive plumage and is sexually mature. At this stage, the bird is ready to mate and breed.