Bird Life Cycle

May 26, 2023, 16:45 IST

Birds are animals that have evolved to live in the air. They can fly because their wings are mighty and their bodies are light. Birds have a variety of traits that enable them to survive in the air, such as feathers that function as insulation and aid in flight, a mouth that is uniquely built for capturing prey, and eyes that are designed for both daytime and avian vision.

Most birds release eggs to reproduce. The parents incubate the eggs until they hatch, after which they feed the chicks. Some birds, such as penguins, can care for their young long after they have left the nest.

Birds Introduction

Birds are vertebrates belonging to class Aves. They are warm-blooded. They are four-chambered. Birds fly with the help of forelimbs and use hind limbs to rest. They lay hard-shelled eggs that are hatched in warm conditions.

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Birds Evolution

• It's still not entirely understood how birds evolved. Bird bones are brittle than other vertebrates, so they also do not fossilise.
• As diapsids, birds have two fenestrations, or apertures, in their heads. Crocodiles and dinosaurs are also members of the diapsid group called the archosaurs, including birds. It is generally acknowledged that birds descended from dinosaurs.
• Dinosaurs were divided into the Saurischia ("lizard-like") and the Ornithischia subgroups. ("bird-like").
• Despite the names of these groupings, it was not the dinosaurs that resembled birds that gave origin to contemporary birds.
• Saurischia instead split into two distinct groups. One of them includes long-necked herbivorous dinosaurs like Apatosaurus.
• Theropods, a second group of bipedal carnivores, are the ancestors of modern birds. Similarities in the hip and wrist bone structures of theropod fossils and those of birds and the presence of the wishbone, created by the fusion of the clavicles, point to this development route.
• Archaeopteryx, a Jurassic-era fossil with traits of dinosaurs and birds, is a notable example of an animal transitional to dinosaurs and birds. while some experts suggest designating it as a bird, Others intend to describe it as a dinosaur; Archaeopteryx's fossilised skeleton resembles a dinosaur's.
• The precise process by which avian flying developed is still unknown. The arboreal ("tree") hypothesis and the terrestrial ("land") hypothesis are the two primary hypotheses.
• The arboreal theory postulates that before becoming completely capable of flapping flight, the ancestors of contemporary birds that lived in trees leapt from branch to branch utilising their feathers as gliding devices.
• The terrestrial theory, in contrast, contends that running catalysed flight since wings could be employed to facilitate running before being adopted for flapping flight.
• It is still unknown how endothermy developed in birds, just as how flying developed. Feathers offer insulation. However, this is only advantageous if internal body heat production occurs.
• Similar to external heat generation, internal heat production depends on insulation to keep the heat inside. It has been proposed that either endothermy or feathers developed in response to different selection pressure.
• The dominating bird species throughout the Cretaceous epoch was a group known as the Enantiornithes. Enantiornithes, which translates to "opposite birds," refers to the fact that some foot bones are linked differently than in current birds.
• These birds did not live through the Cretaceous and established a distinct evolutionary branch from contemporary birds.
• The Cretaceous also saw the emergence of Ornithurae birds, a branch of the evolutionary tree that contains modern birds and Enantiornithes.
• Modern birds took over as the dominating bird after the demise of Enantiornithes, and significant radiation took place throughout the Cenozoic Era.
• Modern birds are now divided into two groups, the Paleognathae ("old jaw") or ratites (a group of flightless birds that includes ostriches, emus, rheas, and kiwis), and the Neognathae ("new jaw"), which includes all other birds. These modern birds are called Neornithes ("new birds").

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Characteristics of Birds

1. As we know, birds belong to the class Aves.
2. They are Homeothermic or Warm-blooded.
3. Their Forelimbs are modified into wings, which helps in flying.
4. Hind limbs pair helps in different functions like walking, perching, grasping, hoping, wadding, and swimming.
5. Feathers cover the body to maintain warmness by preventing heat loss.
6. The digestive system of birds has crop and gizzard, which help soften and crunch food.
7. Birds have a voice box known as a syrinx at the base of the trachea. It gives particular melodious sounds.
8. Respiration is carried by spongy elastic lungs upon which air sacs are attached.
9. Double circulation is present, and blood is pumped by a four-chambered heart. Blood contains haemoglobin and nucleated, biconvex RBCs.
10. Birds are uricotelic, and the excretory system has metanephric kidneys.
11. Birds are unisexual and show sexual dimorphism.
12. Fertilisation is internal in them, and birds are oviparous.

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Bird Life Cycle

• Stage 1 - The Egg

The First stage of a bird's life starts inside an egg, where the egg has a white, yellow, hard shell covering the undeveloped embryo. The number of eggs the bird lays, and its size differs from species to species. The eggs are brooded by one of the parent birds for the developing embryo to form into a chick. The baby bird's beak has a complex and bony structure known as the egg tooth. So for hatching purposes, the baby bird utilises the egg tooth to break the eggshell.

• Stage 2 - The Hatching

This is the second stage at which the bird emerges from the egg, where the newly hatched bird is known as a hatchling or chick. Hatchlings have soft feathers and cannot fly. Birds at this stage need extra care for their growth, and predators also threaten birds. When a hatchling develops and is cared for by its parents inside the nest, it is called to be nestling.

• Stage 3 - The Nestling

At this stage, the bird is cared for and nourished by his parents, and the bird starts trying to fly. When the nestling completes its flight capacities and is set to take its first flight, the bird is known as a fledgeling.

• Stage 4 - The Fledgeling

This is the stage where the bird is all set to fly but up to a limited distance. Birds at this stage have completely developed plumes and solid muscle wings. The period of this stage in birds changes starting with one stage and then onto the next.

• Stage 5 - The Juvenile

At this stage, plumage begins appearing, and the bird resembles an adult bird. Also, the bird is all set to fly independently. Plumage can be defined as the layer of feathers covering a bird's exoskeleton. But the juvenile birds are unable to breed at this stage.

• Stage 6 - The Sub Adult

This stage can be characterised as young birds do not have adult plumage, and they are not sexually mature too. Also, there are some variations in that some bird species mature at this stage while others do not.

• Stage 7 - The Adult

At this stage, the bird is called an adult and is fully sexually mature and has adult plumage. Also, at this stage, the bird is now able to mate and can also perform breeding.

Bird Life Cycle: FAQs

Q1. Why do birds have feathers?

Ans. Feathers on birds are mainly used to regulate body temperature. The feathers on the wings help in the process of flying. For males, colourful feathers are an attractive tactic to charm females during the breeding season.

Q2. What is a bird's life cycle?

Ans. A chick is a newly hatched bird that needs protection and assistance from its parents to feed. A bird that has acquired flight feathers and takes flight on its own to develop and flourish is referred to as a young bird. A bird that has reached adulthood and is prepared for mating is called an adult bird.

Q3. What bird is the youngest?

Ans. An infant bird is referred to as a hatchling. It is completely defenceless and mainly or entirely bare. Hatchlings cannot walk or perch; therefore, they remain within the nest. Although older than hatchlings, nestlings are still in the nest and cannot perch or walk properly.

Q4. How long have birds been around?

Ans. Theropod dinosaurs gave rise to birds during the Jurassic Period (around 165–150 million years ago). Rather than developing suddenly, the characteristic bird body type of tiny, light, feathered wings evolved gradually over millions of years.