Birds, members of the class Aves, include more than 10,400 living species. Their feathers distinguish them from all other classes of animal; no other animals on earth have them. If you see an animal with feathers, it’s undoubtedly a bird. Like mammals, birds are warm-blooded vertebrates with four-chambered hearts. However, they are more closely related to reptiles and are believed to have evolved from dinosaurs. Their forelimbs have been modified into wings over many millions of years of evolution, they lay hard-shelled eggs and they have exceptional vision – the most acute of their senses. Most birds are diurnal, meaning they sleep at night. Most can fly, but flightless species exist.
Five Top Bird Characteristics
Certain identifying characteristics distinguish birds from other classes of animals. Five especially important distinguishing characteristics of birds include:
Feathers
All birds have feathers, which are actually highly evolved scales. In fact, birds have scales on their feet – the clearest reminder of their close relation to reptiles. As noted above, feathers are not found on any other class of animal. Like nails and hair on humans, feathers are made out of keratin. They serve a number of purposes, from providing warmth to assisting in the ability to fly. Most birds shed, or molt, their feathers one or two times per year. Contour feathers help birds to fly effectively and create a streamlined body shape. Soft, fluffy feathers provide warmth. Flight feathers, found on the wings and tail, provide loft. Male birds also often use their feathers to attract mates.
Wings
Wings are a primary characteristic of birds, but they are found on other types of animals too. For example, bats are flying mammals with wings, and many types of insects have wings. Strong muscles in the chest help to propel wings, allowing for flight. Bird bodies are curved specifically to give lift to the wings. Different wing shapes provide different advantages, depending on species. For example, wings that have sharp, narrow tips allow for greater speed. Wings that are longer than they are wide make it easier for birds to soar for extended periods of time. Elliptical, evenly shaped wings, which are most notably found on songbirds, allow for small, quick movement. Birds that are capable of swimming, like penguins and puffins, have wings that are shaped like flippers.
Beaks
All bird species have beaks, or bills – bony concentrations that are surrounded by layers of keratin. The shape of a bird’s beak provides strong clues about its dietary habits. Although some birds have tumia, sharp ridges along the edges of their beaks, none possess true teeth. Therefore, the beak plays a crucial role in feeding. Birds that primarily subsist off of seeds, for example, tend to have strong, cone-shaped beaks. Ducks, geese and other types of waterfowl have broad, flat beaks that are designed to help them strain food from water. Meat-eating birds like owls and hawks have sharp, hooked beaks that they use to grind, tear and rip their prey to shreds.
Eggs
Egg laying is another characteristic that is common to all birds, or members of the Aves class. However, it is not unique to this class of animals, as reptiles, fish, amphibians and insects also all lay eggs. Birds’ eggs have hard shells that are mostly made out of calcium; a layer of hardened mucus helps to keep them intact. Within an egg, the embryo gets its nutrition from the yolk and the egg white, which is known as albumin. The vast majority of bird species build nests for their eggs and proceed to care for the hatchlings until they are capable of fending for themselves. In most species, both males and females play important roles in caring for the young.
Nearly all birds incubate their eggs. Exceptions include megapodes, or mound builders, which rely on external heat sources like decaying vegetation, and brood parasites. The latter, including cuckoos and cowbirds, prefer to lay their eggs in other birds’ nests. Some birds, like murres and certain penguin species, don’t use nests at all, choosing instead to rest eggs on the tops of their feet during incubation. Incubation periods range from 11 to 80 days depending on species.
A set of eggs that is laid at one time is called a clutch. Anywhere from one to 20 eggs or so may be found in a single clutch. Some birds engage in determinate laying, meaning that they lay the same number of eggs per clutch every time. Most birds engage in indeterminate laying, meaning that the number per clutch varies.
Skeleton
Flightless species of birds have heavy bones that are filled with marrow. Birds that are capable of flight – in other words, most birds – have lightweight skeletons made up of hollow bones. Their skeletons have many fused bones, including collarbones, which help them to brace their wings effectively during flight. Birds have large breastbones, or sternums, that provide sturdy points of attachment for muscles of the wings.
Notable Types of Birds
Today, there are more than 10,400 extant bird species in the world. Across North America and South America, there are more than 4,400 species of the Aves class. Approximately 2,700 different species are found in Asia, and another 2,300 or so are found in Africa. More than 500 species are found in Europe west of the Ural Mountains, and more than 700 species are found in Russia. Costa Rica has one of the highest concentrations of bird species – roughly 800.
Some of the most notable types of birds include:
- Birds of Prey – This group is made up of more than 300 species of birds, including eagles, hawks, ospreys, falcons and vultures.
- Cranes – This group, which includes coots and rails, boasts more than 200 species.
- Game Birds – Perhaps the best-known type of bird, game birds include chickens, turkeys, quails and megapodes. There are approximately 250 species of game birds in the world.
- Herons and Storks – More than 100 species are found in this group, which includes egrets, spoonbills and ibises.
- Hummingbirds and Swifts – The smallest category of birds, this group includes more than 400 different species.
- Ostriches – The ostrich, the most famous flightless bird, is also the only species in its genus. It also holds the distinction of being among the largest birds.
- Owls – Another important type of bird is the owl. There are more than 200 species of owls across the world.
- Parrots and Cockatoos – This colorful group, which includes macaws, cockatiels and budgerigars, consists of more than 350 species. They are popularly kept as pets.
- Penguins – There are roughly 20 species of this flightless bird in the world.
- Perching Birds – Also known as passerines, this group includes more than 5,000 species, making it the largest and most diverse. Common types of perching birds include crows, swallows, jays, finches, sparrows, wrens, starlings and larks.
- Pigeons and Doves – This group includes more than 300 bird species. Pigeons are famous for ferrying messages for humans, and have been used in such a way since Roman times. They were also used during World War I and II and the Korean War.
- Shorebirds – More than 350 species are found in this group, including sandpipers, terns, oystercatchers and gulls.
- Waterfowl – Ducks, geese, swans and many other birds belong to this group, which includes more than 150 species.
- Woodpeckers and Toucans – Known for their distinctive beaks, this group is made up of more than 400 species.
Evolution of Birds
The evolution of birds has been a topic of much debate for many centuries. Today, the most commonly accepted theory, the theropod ancestor hypothesis, posits that birds evolved from theropod dinosaurs during the Jurassic period, which happened between 165 million and 150 million years ago. Theropod dinosaurs were two-legged dinosaurs, and the T. Rex is included among their ranks.
The earliest known bird on the fossil record, archaeopteryx, was a hybrid between a bird and a dinosaur. It had feathered wings like a bird but also had sharp teeth and a long, bony tail like a dinosaur. This and other types of early birds diversified rapidly throughout the Jurassic and Cretaceous periods. They quickly became capable fliers and exhibited extremely rapid growth rapids. However, their populations were decimated by the major extinction event that eliminated dinosaurs entirely. After that point, modern birds diversified at an explosive rate, and there are now more than 10,000 different species all across the world.
Types of Birds

Adelie Penguin
Eats up to 2kg of food per day!

African Penguin
The only penguin species in Africa!

Albatross
The largest wingspan of any bird in the world!

Aurochs
Extinct ancestor of all domesticated cattle!

Avocet
Has a curved, upturned beak!

Barn Owl
Found everywhere around the world!

Bird
Not all birds are able to fly!

Birds Of Paradise
There are around 50 different species!

Blue Jay
Blue jays rub ants on their feather to remove harmful acids

Booby
Seabirds found across the South Pacific!

Budgerigar
Natively found in Australia!

Cassowary
Can reach speeds of 30mph!

Chicken
First domesticated more than 10,000 years ago!

Chinstrap Penguin
There are 7 million breeding pairs!

Cockatoo
Highly social, smart, and chatty bird.

Common Buzzard
The most common raptor in the UK!

Common Loon
Also known as the Great Northern Diver

Cooper’s Hawk
Eyes change color as they age

Crane
Many are critically endangered species!

Crested Penguin
Has long yellow eyebrows!

Dodo
Native to the island of Mauritius!

Duck
Rows of tiny plates line their teeth!

Eagle
Has exceptional eyesight!

Emperor Penguin
The world's largest species of penguin!

Emu
The largest bird in Australia!

Falcon
The fastest creatures on the planet!

Flamingo
Sleeps on just one leg!

Frigatebird
Found inhabiting tropical islands and coasts!

Galapagos Penguin
Found around the Equator!

Gentoo Penguin
Found throughout the sub-Antarctic!

Golden Masked Owl
While flying high above this owl can hear a mouse moving in the tall grass of field!

Golden Oriole
Migrates between Europe and Asia!

Goose
There are 29 different species!

Gouldian Finch
The male Gouldian finch bobs its head and fluffs its feathers to court a female.

Green Bee-Eater
Mainly eats honeybees!

Grouse
Feathered legs and toes!

Guinea Fowl
Found in a vairety of African habitats!

Harpy Eagle
Talon's the size of a grizzly bear's claws!

Hawaiian Crow
Once believed to be a family guardian spirit in Hawaii

Heron
Inhabits wetlands around the world!

Hoopoe
Stunning bird with a stinky way to deter predators!

Hornbill
The bird has a massive horn on its bill!

House Finch
The house finch can become redder depending on what it eats

Humboldt Penguin
Found on the South American coast!

Hummingbird
Beat their wings up to 80 times per second!

Kakapo
The heaviest species of parrot in the world!

Keel-Billed Toucan
It's beak can reach nearly 20 cm long!

King Penguin
More than 2 million breeding pairs!

Kingfisher
Inhabits wetlands and woodlands worldwide!

Kiwi
Only found in the forests of New Zealand!

Little Penguin
The smallest species of penguin!

Long-Eared Owl
Ear tufts make it look bigger!

Macaroni Penguin
Gather in colonies of up to 100,000 members!

Macaw
The largest species of parrot in the world!

Magellanic Penguin
Threatened by oil spills!

Magpie
They are found across Europe, Asia and Africa!

Mourning Dove
It is almost always the male who makes the famous sad sound, which is a wooing call

Nightingale
Named more than 1,000 years ago!

Ostrich
The largest bird in the world!

Parrot
Can live for up to 100 years!

Peacock
Most commonly found on the Indian mainland!

Pelican
Can have a wingspan of up to 3 meters!

Penguin
Spends 75% of it's time hunting for food!

Peregrine Falcon
Fastest animal on Earth

Pigeon
They can find their way back to their nests from up to 1300 miles away.

Pileated Woodpecker
Pairs establish territories and remain all year

Puffin
Can remain in the water for up to 2 minutes!

Purple Finch
The intensity of the plumage can change based on what the bird eats

Quail
Inhabits woodland and forest areas worldwide!

Quetzal
The tail feathers of the male can be 1m long!

Red Finch
Red finches can form flocks of over 100 birds.

Robin
There are more than 45 species in Australia alone!

Rockhopper Penguin
There are 3 different species!

Roseate Spoonbill
The only Spoonbill in the western hemisphere!

Royal Penguin
Can reach speeds of 20mph!

Snowy Owl
One of the largest owl species in the world!

Sparrow
There are 140 different species!

Spixs Macaw
One of earth's rarest animals!

Swan
Populations have been affected by pollution!

Tawny Owl
The most widespread owl in Europe!

Toucan
There are more than 40 different species!

Tropicbird
Nests on tropical islands and cliffs!

Uguisu
Their guano is used in face creams!

Umbrellabird
Migrates up and down the mountains!

Vulture
There are 30 different species worldwide!

Wandering Albatross
Featured in “The Rime of the Ancient Mariner”

Whooping Crane
This species is named after the loud whooping sound it makes

Woodpecker
There are 200 different species!

Yellow-Eyed Penguin
The rarest species of penguin!
List of Birds
- Adelie Penguin
- African Penguin
- Albatross
- Aurochs
- Avocet
- Barn Owl
- Bird
- Birds Of Paradise
- Blue Jay
- Booby
- Budgerigar
- Cassowary
- Chicken
- Chinstrap Penguin
- Cockatoo
- Common Buzzard
- Common Loon
- Cooper’s Hawk
- Crane
- Crested Penguin
- Dodo
- Duck
- Eagle
- Emperor Penguin
- Emu
- Falcon
- Flamingo
- Frigatebird
- Galapagos Penguin
- Gentoo Penguin
- Golden Masked Owl
- Golden Oriole
- Goose
- Gouldian Finch
- Green Bee-Eater
- Grouse
- Guinea Fowl
- Harpy Eagle
- Hawaiian Crow
- Heron
- Hoopoe
- Hornbill
- House Finch
- Humboldt Penguin
- Hummingbird
- Kakapo
- Keel-Billed Toucan
- King Penguin
- Kingfisher
- Kiwi
- Little Penguin
- Long-Eared Owl
- Macaroni Penguin
- Macaw
- Magellanic Penguin
- Magpie
- Mourning Dove
- Nightingale
- Ostrich
- Parrot
- Peacock
- Pelican
- Penguin
- Peregrine Falcon
- Pigeon
- Pileated Woodpecker
- Puffin
- Purple Finch
- Quail
- Quetzal
- Red Finch
- Robin
- Rockhopper Penguin
- Roseate Spoonbill
- Royal Penguin
- Snowy Owl
- Sparrow
- Spixs Macaw
- Swan
- Tawny Owl
- Toucan
- Tropicbird
- Turkey
- Uguisu
- Umbrellabird
- Vulture
- Wandering Albatross
- Whooping Crane
- Woodpecker
- Yellow-Eyed Penguin
Birds FAQs (Frequently Asked Questions)
What are the four types of birds?
There are far more than only four types, or categories, of birds in the world. If “type” refers to “species,” then the figure is closer to around 10,400. Birds can be classified into different categories in a number of ways, including flightless birds versus birds that are capable of flight and birds that live mostly on land or near water.
How are birds identified?
Birdwatching, a popular pastime, involves identifying birds in the wild. Four things are looked to when identifying birds: their size and shape, their behavior, their habitat and their color patterns. By learning the basics of each of these categories, birdwatchers can identify birds in the wild more quickly – an important aspect of the sport.
Why do birds bathe?
Bathing is a vital part of feather maintenance. Water helps to loosen up dirt and other debris that has worked its way into the feathers. Once freed of dirt, the feathers are easier to preen. During preening, birds rearrange their feathers and dispense oil from the preen gland, ensuring that their feathers remain waterproof. This also traps an insulating layer of air beneath, helping to keep the bird warm.
Which birds cannot fly?
Some of the best-known examples of flightless birds include penguins, ostriches, emus, cassowaries and kiwis.