What makes a bird different from another bird? Scientists used to group birds by their overall appearance, but that? changed as we learn more about genetics.
When I was in middle school I was given a page-a-day bird calendar for Christmas. At the end of the year I had a drawer filled with 365 colored photos of my favorite taxonomic group: Birds. In a half-dozen zip-locked bags, I organized the birds based on color. After a few weeks, I unzipped the bags and reorganized them by beak shape, then by habitat range and finally by dietary preferences.
I am not the first person to try and sort out the extravagant world of birds. By 1758 in the 10th edition of Systema Naturae, Carl Linnaeus developed a system of classifying living organisms using seven levels. With the help of a common childhood mnemonic device, I bet you can still remember the order: “King Phillip Came Over For Good Spaghetti,?which stands for Kingdom, Phylum, Class, Order, Family, Genus and Species. Kingdom is the largest level comprising of the most things, with species being the smallest. But what makes a species a species?
“A frequent rule of thumb is like breeds with like,?said Dr. Thomas S. Schulenberg, research associate of Cornell Lab of Ornithology. “That is, a species is a collection of individuals that breed amongst themselves, but not with others.?lt;/span>
That? true. According to “Understanding Evolution,?a collaborative website from the University of California Museum of Paleontology and the National Center for Science Education that teaches the science and history of evolutionary biology:
“A species is often defined as a group of individuals that actually or potentially interbreed in nature. In this sense, a species is the biggest gene pool possible under natural conditions.?lt;/span>
Schulenberg said that different species simply look different from one another.
“Blue jays and bluebirds look, sound and behave differently, and do not interbreed; ditto goldfinches and yellow warblers,?and the list goes on. However things can get tricky when we start trying to apply this simple rule when comparing populations that are geographically separated.
How sure can we be that the Yellow Warblers that breed in mangroves around the Caribbean really are the same species as the Yellow Warblers that breed in small willows in Alaska?
“Most ornithologists would argue that if, even across large distances or across gaps ?such as between continents and islands, or from one island to another ?these populations still sound and act pretty much the same, then they still are the same species,?Schulenberg said.
However, different scientists could view the same two populations and be more inclined to classify these as separate species. This is one of the many reasons why there is no single count of the number of species, only different estimates. “Estimates vary, but not by a lot,?Schulenberg said. He adds that it is in the range of 10,500 species of birds, with 39 orders* recognized.
Birds are classified on the basis of anything and everything, much like I was trying to accomplish with my ziplock bags. “Two hundred years ago, birds were classified on the basis of overall external appearance: size, shape, color, what type of bill it had and so on,?Dr. Schulenberg points out.
That is to say if it looks like a duck, swims like a duck ?it’s a duck. That system does work well for very distinctive “body plans”, such as those of a ducks, flamingos, woodpeckers or corvids but begins to break down when dealing with the other 10,000-some species.
The good thing about classifying birds is that they are all basic variations on a single theme ?feathers/the requirements for flight ?and as a group are much less variable than mammals (just think about think the family resemblance with dolphins, manatees, cows and bats).
Shulenberg says beginning about 100 years ago, internal anatomy was added to classify birds. Details of the musculature and of the bumps on bones (especially of the skull) were added to help find commonalities and relatedness. “This helped a bit, but still left many ornithologists feeling uneasy about many aspects of bird classification,?he added.
Blue jays and blue birds may both be blue, but they?e different species and will not breed.
How DNA Studies Have Changed How We Group Birds
Bird taxonomy had several changes in the past 50 years and especially in the last 20, with the start of computers. This technology made it possible to combine large amounts of data on species easier than before. With the revolution in genetics, scientists can collect genetic information directly from a bird’s DNA and compare that to DNA of many other species.
“The results of this genetic revolution have, in many ways, completely upended the historical ideas of bird classification,?Schulenberg said. “Vireos, for example, are small green insectivorous birds, similar in size and behavior to warblers. Vireos and warblers used to be thought of as a relatives; open any old field guide ?one from 20 or more years ago ?and vireos and warblers are shown side by side.?lt;/span>
Today, due to DNA we know that although vireos are small and superficially resemble warblers they actually are more closely related to crows, jays, and shrikes. I will now have to consult my zip lock bags to see if I had correctly identified them.
Parrots, like this king parrot, are part of the Psittaciformes order.
Orders Of Birds List
* Editor? Note: The number of bird orders can range depending on the source (some sources list 23 orders while others list 40), so we?e chosen to feature BirdLife International? 2014 bird taxonomy list. This list only contains 30 orders, which differs from the 39 orders Dr. Thomas S. Schulenberg references above. As BirdLife writes in their taxonomic approach:
“The BirdLife Taxonomic Working Group (BTWG) sets the standards by which BirdLife takes and implements decisions on bird taxonomy and nomenclature. It aims to ensure that BirdLife’s Checklist of the world’s bird species evolves in a structured, documented, transparent and defensible way. The BTWG now uses a set of criteria by which species rank can be consistently assessed where this is necessary (e.g. for newly described or split species published subsequent to the main sources). These criteria (Tobias et al. 2010) involve weighting morphological and acoustic differences as compared with the nearest believed relative, and are particularly intended to help make decisions involving allopatric taxa (as opposed to those in sympatric, parapatric or hybrid zones situations where the situation is generally clearer).”
The orders include:
1) Accipitriformes: This order includes hawks, eagles, old and new world vultures, ospreys and secretarybirds.
2) Anseriformes: This order includes ducks, geese, swans, screamers, and magpie goose.
3) Bucerotiformes: This order includes hoopoes, wood hoopoes, scimitarbills, hornbills and ground hornbills.
4) Caprimulgiformes: This order includes the night birds, such as the nightjars, frogmouths, potoos and the oillbirds.
5) Charadriiformes: This order is large, and consists of many shorebirds and relatives. This includes the auks, skuas, jaegers, gulls, terns, skimmers, plovers and many more.
6) Ciconiiformes: This order includes storks such as the openbills, Marabou stork, wood stork, the black-necked stork and the Jabiru.
7) Coliiformes: Mousebirds make this order, including the speckled mousebird, the white-headed mousebird and the blue-naped mousebird.
8) Columbiformes: Pigeons and doves make this order. Some of the pigeons and doves are the diamond dove, the European turtle dove, the extinct dodo and the extinct passenger pigeon.
9) Coraciiformes: This order includes kingfishers, bee-eaters, rollers and their relatives.
10) Cuculiformes: This order includes the cuckoo birds, such as the couas, coucals and roadrunners.
11) Gaviiformes: This order includes the loons, such as the red-throated loon and the yellow-billed loon.
12) Galliformes: This order includes quails, guans, currasows and megapodes, including chickens, pheasants and Guinea fowl.
13) Gruiformes: This order includes cranes, rails and coots.
14) Falconiformes: Like the name suggests, this order includes the falcons, include black caracars, falconets and kestrels.
15) Leptosomiformes: The cuckoo roller is the only bird in this order. Sometimes this bird is placed with the Coraciiformes (kingfishers, and bee-eaters) but DNA studies make its exact position unclear.
16) Mesitornithiformes: These include the mesites birds, which were usually grouped with Columbiformes or doves. New DNA research indicates they might be in a sister group to the doves.
17) Musophagiformes: This order includes the turacos, the go-away-birds and the plantain-eaters.
18) Opisthocomiformes: The only bird in this order is the hoatzin, also known as the stinkbird. The Wikipedia page on this bird says:
“The hoatzin was originally described by German zoologist Statius M??r in 1776. There has been much debate about the hoatzin’s relationships with other birds. Because of its distinctness it has been given its own family, the Opisthocomidae, and its own suborder, the Opisthocomi. At various times, it has been allied with such taxa as the tinamous, the Galliformes (gamebirds), the rails, the bustards, seriemas, sandgrouse, doves, turacos and other Cuculiformes, and mousebirds. A whole genome sequencing study published in 2014 places the hoatzin as the sister taxon of a clade composed of Gruiformes and Charadriiformes.
In 2015, genetic research indicated that the hoatzin is the last surviving member of a bird line that branched off in its own direction 64 million years ago, shortly after the extinction event that killed the dinosaurs.”
19) Otidiformes: This order includes the Great Bustard bird and the Little Bustard bird.
20) Passeriformes: There are a lot of passerine birds, and is the largest order of birds. Commonly known as perching birds or songbirds, this includes, finches, crows, wrens and jays.
21) Pelecaniformes: Much like the name, this order includes pelicans, as well as shoebills, gannets, ibises, herons and more.
22) Piciformes: This order includes woodpeckers, puffbirds, toucans and barbets.
23) Podicipediformes: This order includes the grebes, like the little grebe, the pied-bill grebe and the Western grebe.
24) Procellariiformes: This order includes albatrosses, petrels and shearwaters.
25) Psittaciformes: This order should be familiar for anyone who reads BirdChannel ?this order includes parrots, cockatoos, lories and lorikeets.
26) Sphenisciformes: This order includes the penguins, such as the Emperor penguins and Aedelie penguins.
27) Strigiformes: This order includes the owls, such as barn owls, masked owls, etc.
28) Suliformes: There’s some debate, but experts believe birds that are traditionally grouped with the Pelecaniformes order, such as frigatebirds, boobies and cormorants, should be in their own separate order, the Suliformes.
29) Struthioniformes: This order includes ostriches, emus, rheas, kiwis and cassowaries.
30) Trogoniformes: This order includes the trogons and quetzals.