Bird Life Cycle

Introduction

The animal kingdom is vast with extremely diverse living organisms. The flying animals are commonly referred to as birds although they are systematically placed under the Class Aves. It includes all the feathered homeothermic, warm-blooded animals with specialised organs for flying. It includes more than 10,000 species. Their sizes vary from tiny two-inch-sized hummingbirds to 9 feet-tall ostrich which are the largest of all birds. Morphological features like a beak (shape and size), wing size, nutrition, and plumage differ with the species and each characteristic has its unique importance in the species survival and continuance.

Characteristics

Although the members of class Aves show extreme diversity the general characteristics of the class are listed below.

• Homeothermic (warm-blooded organisms capable of maintaining their internal body temperature irrespective of the surrounding environment).

• Teeth less beak is a modification of upper and lower jaws. Beaks can be pointed, conical, short, chisel-like or hook-like based on the feeding pattern.

• Forelimbs are modified into wings that aid in flying. Although bats (mammals) also possess wings, both the organisms differ in structure and feathery wings supported by bones are the unique feature of birds. Bird wings are supported by well-developed flight muscles which aid in lifting and flying.

• Hind limbs pair perform different functions like walking, perching, grasping, hoping, wadding, and swimming.

• The body is covered by feathers to maintain warmness by preventing heat loss. Flight and contour feathers facilitate flying. The plumage marks the uniqueness of a species and is an attractive feature for finding a mate.

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• Long bones of flight birds are hollow with air cavities and are called pneumatic bones. Flightless birds like penguins have bones with bone marrow which help them survive in extremely cold weather.

• The digestive system is equipped with crop and gizzard both of which are associated with softening and crushing of food respectively.

• Birds have a voice box called a syrinx at the base of the trachea. It gives special melodious sounds.

• Respiration is carried by spongy elastic lungs upon which air sacs are attached.

• Double circulation is present and blood is pumped by a four-chambered heart. Blood contains haemoglobin and nucleated, biconvex RBCs.

• Birds are uricotelic and the excretory system is equipped with metanephric kidneys.

• The nervous system is highly evolved with a large brain and well-developed cerebellum that facilitate flight.

• Birds are unisexual and exhibit sexual dimorphism. They are monodelphic with a single ovary and oviduct lying on the left side.

• Fertilisation is internal and birds are oviparous. They lay amniotic eggs from which the young ones develop. Parental care is a typical characteristic of the class.

The life cycle of birds

Some birds finish their life cycle in their own ecosystem or surroundings. Some species migrate to new places to find a mate and lay eggs.

Stage 1 − Egg stage

Birds are oviparous and life starts from a single egg laid by the parent bird. The egg bears an embryo that develops into a young one. It is contained within a hard, yellow or white shell. During development, the embryo grows a structure called an egg tooth on its beak. It facilitates the breaking of eggshells and chicks emerge out.

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Stage 2 − Hatching

The newly emerged young bird that came out of an egg is called a hatchling. The hatchling has soft feathers and is not capable of flying. It is vulnerable to predator attacks. Hatchling requires utmost parental supervision.

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Stage 3 − Nestling

A nestling is fed by parent birds and is a growing up hatchling. As the nestling grows up it gains flying capabilities getting ready for the first flight and is called a fledgling.

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Stage 4 − Fledgling

Fledgling is the stage where a young one is ready for flying and takes its first flight. It possesses strong flight muscles and has completely grown its feathers. Although a fledgling is capable of flying, it takes only short distances from the nest and is still under parental care.

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Stage 5 − Juvenile

Once the young bird attains the juvenile stage, it is ready for independent living and can fly off the nest. At this stage, it looks slightly similar to an adult bird. Although the feathers have similarities to those of the adult body, birds at this stage are not capable of reproducing. The feathers are still soft at this stage.

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Stage 6 − Sub adult

Depending on the species, some birds at this stage attain sexual maturity. At this stage, birds do not have the same plumage as the parent body.

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Stage 7 − Adult

Birds attain the adult stage when they develop feathers entirely similar to the parent body and are capable of finding a mate and reproducing.

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Conclusion

The members of class Aves in Animal kingdom are birds. Birds adopt the aerial mode of living. They have certain features aiding their flight capabilities. Birds have toothless beaks, feathered wings supported by strong muscles, and pneumatic hollow bones for an aerial mode of life. Birds are unisexual and exhibit sexual dimorphism. The Life cycle of birds starts with the single-celled egg stage. Birds are oviparous and lay eggs. The parent bird sits on the eggs until they hatch and the young ones hatch out. They develop into complete adults and their life cycle has seven stages. The length of each stage varies with the species.

FAQs

Q1. How many eggs do a bird lay?

Ans. Clutch is the total number of eggs laid by a bird in a single nesting cycle. Although the number of eggs in a clutch varies from species to species, most birds lay a single egg in a day.

Q2. Do birds lay unfertilised eggs?

Ans. Sometimes, birds lay unfertilised eggs containing the genetic material of only the female parent. However, only the fertilised eggs with the genetic material of both parents develop into young ones.

Q3. What is the purpose of the bird's beak?

Ans. In birds, the beak is a modified toothless upper and lower jaws. The birds build nests, eat, feed their young ones, clean their feathers, and defend themselves with the help of beaks.

Q4. What is the purpose of feathers in birds?

Ans. Birds have feathers which are mainly concerned with controlling body temperature. The feathers on wings help in flight mechanisms. In males, the coloured feathers are an attractive strategy followed by males to attract females for courtship during the breeding season.

Q5. What is a brooding patch?

Ans. Brooding patch is featherless skin on an adult bird's abdomen. It is richly supplied with blood vessels and provides heat for the eggs to hatch when the parent bird sits on them.