Classification of Birds - Summary

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Birds are the second class of vertebrate animals with the largest number of species on the planet. At present, approximately 10,000 species of live birds have been described and it is estimated that there could currently be around 10,000 more unrecognized species. In order to easily identify and differentiate the individuals of each species, biologists, taxonomists and ornithologists have grouped and cataloged them according to their morphological, phylogenic and behavioral characteristics.

In this interesting article by Ecologist Verde on the classification of birds, we show you some of the most common classifications of birds, ranging from the orders of birds following their taxonomy to the types of birds according to different criteria such as, for example, their capabilities in certain aspects or their relationship with other species of birds and with human beings.

Bird characteristics

Regardless of their order, family, and genus, all species of modern birds they have the following characteristics:

  • Birds are a class of animals belonging to the Animalia kingdom, the Chordata phylum and the Vertebrata subphylum.
  • They are heterotrophic, aerobic, warm-blooded organisms with accelerated metabolism.
  • They are tetrapods and bipeds. Their front limbs evolved into wings and although not all fly, the vast majority do.
  • They have a heart with four chambers, they have a cloaca and also hollow bones that facilitate flight.
  • Their bodies are almost entirely covered in feathers and they have no sweat glands.
  • They have toothless beaks that they use to hold and ingest their food.
  • Their legs are covered in scales and most species have 4 toes on each.
  • They reproduce sexually by means of eggs (they are oviparous) and more than 95% of the species are monogamous during one or more breeding seasons.

We can classify birds in many ways: according to their taxonomy, their anatomy, their way of moving, their eating habits, the place where they live, and even, according to the relationship they have with other species of birds and with humans.

To have more information about its characteristics, you can consult this other article by Green Ecologist: Main characteristics of birds.

Classification of birds according to their order

Taxonomically, we can classify birds simply and efficiently according to their order. There are several orders of birds, but the most representative are:

  • Order Passeriformes or passeriformes: It is the order of birds with the most species recorded in the world. It is made up of between 5700 and 6500 species and its members are commonly called birds or songbirds. They are characterized by being small, flying, nesting and having 4 toes on each leg. Some of the most representative species of this order are canaries, sparrows, finches, crows and goldfinches.
  • Order Apodiformes: order made up of hummingbirds, swifts and salanganas. It is the second most diverse order of birds, since it is estimated that there are around 450 current species. Its most distinctive feature is its tiny legs.
  • Order Piciformes: to this order belong the woodpeckers, toucans and bearded ones. It is estimated that there are between 340 and more than 450 species of piciform birds. Most of the species are zygodactyl.
  • Order Psittaciformes or psitácidos: made up of almost 400 species of parrots and cockatoos. They are characterized by living in tropical and temperate areas and have a thick, curved bill and clawed zygodactyl legs. Macaws, Australian parakeets, lovebirds, and common cockatoos belong to this order.
  • Order Columbiformes: pigeons and doves belong to this order. It is composed of approximately 350 current species of herbivorous and flying birds of small-medium size and more than 10 species of extinct birds (among which the dodo stands out).
  • Order Charadriiformes or caradriformes: more than 350 species that live and feed near water belong to this order. Includes seagulls, plovers, and puffins.
  • Order Galliformes or gallinaceas: they are terrestrial poultry. Almost 300 species belong to this order, including chickens, domestic turkeys, peacocks, partridges, quail and guacharacas. They are not very good fliers and in most species there is a marked sexual dimorphism.
  • Order Anseriformes: they are the aquatic fowl. More than 160 species belong to this order, including goose, ducks, geese, and swans. Most are flying, migratory, and herbivorous.
  • Order Falconiformes: they are the more than 300 species of diurnal birds of prey. They are characterized by their excellent vision, their hook-shaped bill, and their long, sharp claws. Falcons, vultures and eagles belong to this order, like the one in the image below.
  • Order Strigif.webpormes or strigif.webpormes: are the more than 200 species of nocturnal birds of prey. They have excellent hearing, thick plumage, and huge eyes facing the front of the head. Owls and owls belong to this order.
  • Order Pelecaniformes: more than 70 species belong to this order, including pelicans and herons. They have webbed feet with 4 toes on each and feed primarily on fish and shellfish.
  • Order Ciconiiformes: made up of almost 20 species of long-necked, aquatic and wading birds. Storks, tantalums and marabou belong to this order.
  • Order Sphenisciformes: they are flightless seabirds. The 17 current penguin species belong to this order.
  • Order Struthioniformes or estrucioniformes: Ostriches and other species of extinct flightless birds belong to this group.
  • Order Phoenicopteriformes: group made up of flamingos, parinas and their extinct relatives.

Some other important bird orders are Casuariiformes, Gruiformes, Suliformes, Procellariiformes, Cuculiformes, Cathartiformes, Tinamiformes, Apterygif.webpormes, Caprimulgif.webpormes, Bucerotiformes, Coraciiformes, Podicipediformes, Rheiformes, and Gaviiformes.

Classification of birds according to their anatomy

We can classify the birds according to their anatomical characteristics in various ways.

Classification of birds according to their size

Depending on its body size, a bird may or may not be a bird. There are authors who affirm that a bird is a bird if it measures less than half a meter and weighs less than 1 kilogram.

  • What examples of birds, therefore they are small species, we have the yellow weaver, the wild canary and the Australian parakeet.
  • As examples of ayou see they are not birds, that is, they are big birds, we have the blue-yellow macaw, pelicans and ostrich.

Classification of birds according to their beaks

Depending on the shape and size of the beak, the feeding of a species can be deduced. There are different types of spikes and each one has a specific function. Some types of spikes are:

  • Short, curved hooked spikes: characteristic of birds of prey and scavengers. They are used to tear the meat into small pieces. Eagles and owls have short, curved, hooked beaks.
  • Long, thin beaks: they facilitate the capture of fish, mollusks and other small invertebrates. They are typical of fishing waterfowl. Herons and storks have this type of beak.
  • Short, thick and robust beaks: They are very useful when opening seeds and nuts. Bullfinches, finches, goldfinches, and chickens all have this type of beak.
  • Very fine long beaks: They are used to extract the nectar from the flowers. Hummingbirds are characterized by having this type of beak.
  • Broad, flattened beaks: filter birds have broad, flattened beaks that allow them to filter their food from the water. Ducks, geese, and swans use their broad, flattened beaks to feed efficiently. You can see examples in the image below.

Classification of birds according to their legs

Depending on the number of toes, the presence of claws and the size of the legs, it is possible to know how a species moves and whether or not it has the ability to swim, climb, run or hunt.

  • Depending on the number of fingers, a bird can be didactic (two toes on each leg like ostriches), tridactyl (three toes on each leg like rheas) or tetradactyl (four toes on each leg like passerine birds).
  • Depending on the arrangement of the fingers, a bird can be anissodactyl, sydactyl, zygodactyl, heterodactyl, or pamprodactyl.
  • If you have sharp and curved claws facing down, it is a bird of prey (such as hawks or owls).
  • If they have webbed webbed feet interdigital between the fingers, it is a water bird (such as ducks and penguins).

Classification of birds according to other physical characteristics

You can know many things about a bird by looking at its plumage. Depending on its thickness and attractiveness, for example, it can be determined if it is a species that lives in climates with very low temperatures, such as penguins, or if it is a species that attracts its mate with its feathers during the season. mating, like peacocks. Sexual dimorphism is also an indicator of courtship and mating rituals in species. Birds of paradise, pheasants, and peacocks are markedly sexually dimorphic.

Classification of birds according to their mobility

Depending on the way they move, the birds can be flying or non-flying, running or non-running and swimming or non-swimming. For example:

  • Passerine, psittaciform, and falconiform birds are non-swimming flying birds.
  • Kiwis and kakapos are flightless crawlers.
  • Ostriches, emus, rheas, and cassowaries are flightless running birds.
  • Penguins are flightless swimming birds.
  • Ducks, geese, swans, and pelicans are flying and swimming birds.

Discover here 10 birds that do not fly.

Classification of birds according to their diet

Depending on their diet, birds can be herbivorous, carnivorous, or omnivorous.

  • Herbivorous birds like parrots, pigeons and hummingbirds they feed on plants, fruits, grains, nuts, seeds and / or nectar.
  • Carnivorous birds like eagles, vultures and woodpeckers they can be insectivores, fishermen, scavengers and / or birds of prey, prey or raptors.
  • Omnivorous birds like sparrows and flamingos they have a mixed diet that includes plants and some small animals such as insects, frogs, fish, crustaceans and / or lizards. Here you can read about What flamingos eat.

Classification of birds according to their habitat

Here we indicate the classification of birds according to where they live:

  • Depending on whether they are of fixed residence or not, they can be migratory birds (like swallows) or they can be sedentary birds (like guacharacas). Read in this other post more about migratory birds: names and photos.
  • Depending on the ecosystem they inhabit, they can be terrestrial (like ostriches), aquatic (like penguins) or semiaquatic or amphibious behavior (such as ducks). Here we talk more about Waterfowl: characteristics, types and names.
  • If they spend a lot of time at sea, they are said to be sea birds (like gannets).
  • If they spend a lot of time in the trees, they are said to be arboreal birds (like the parrots in the image below).
  • If they cannot fly and spend a lot of time on the ground, they are said to be crawling birds (like kiwis and chickens).
  • If they like to live near or in human settlements such as cities or suburbs, they are said to be urban birds (such as pigeons, magpies, sparrows, and breams).

Classification of birds according to their relationship with other birds

We can summarize the classification of birds by their relationship with other birds with these criteria:

  • The vast majority of birds are monogamous and some species form lifelong relationships with a single partner, such as swans and lovebirds. Birds that are not monogamous are usually polygamous and polygynous and form harems, such as roosters, rheas and peacocks.
  • When a bird likes to live and move in large groups of its own species, it is said to be part of a flock, flock or flock. Common cheleas, ducks and hides often form flocks.
  • exist social birds that live happily with other types of birds. This behavior is common among parrots, penguins, and ducks.

Classification of birds according to their relationship with humans

Another interesting classification of these animals is the relationship they have with us:

  • Birds that are bred in captivity for food or economic purposes are known as poultry. Chickens, turkeys, and ducks are poultry.
  • When a species of bird finds it difficult to integrate into domestic life, it is said to be a wild species, as is the case with hummingbirds and birds of prey.
  • When a species of bird is endangered or critically endangered it becomes a species protected by humans, as is the case with the California condor and the green macaw.
  • Those birds that are kept as pets are known as songbirds and / or companion birds, as is the case with the royal parrot and the Australian parakeet. Here you can discover 13 birds that sing.

Finally, we want to clarify that there are more ways to classify birds. For example, they can also be divided into diurnal birds and nocturnal birds, according to whether they are more active at some hours of the day or others, but there are more classifying criteria for the species.

If you want to read more articles similar to Classification of birds, we recommend that you enter our Biology category.

  • Maria Luz Thomann. (May 18, 2022). Animal Expert. Types of bird beaks. Available at:
  • Yago Partal. (June 15, 2022). Zoo portraits. Birds, their different beaks and the functions they perform. Available at:
  • Drafting of Aves de Burgos. Birds of Burgos. Available at:
  • Exotic birds web. Available at:
  • IUCN Red List of Threatened Species. Available at:
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