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Quiz: Can You Pick the Closest Relatives on the Tree of Avian Evolution?

Not everything is quite as it seems when it comes to evolution. Try this quiz and see if you can pick out who is related to whom in the bird world.

Illustration of many different birds with a phylogenetic tree graphic of evolution.
Cornell Lab of Ornithology | Birds of the World | Illustration by Jen Lobo.

From the Summer 2024 issue of Living Bird magazine. Subscribe now.

Evolution works in somewhat mysterious ways. Two birds at the same backyard feeder that look alike could be separated by millions of years of evolutionary history. Meanwhile, two birds that are each other’s closest evolutionary cousins could live on opposite sides of the world.

That mixing and matching of birds with different speciation histories is borne of two seemingly opposing forces of evolution. On the one hand, divergent evolution is pushing closely related species away from each other; natural selection (the race to enhance survival, such as being better at exploiting food resources or evading predators) pushes birds to gain an advantage by looking different or moving someplace different.

On the other hand, convergent evolution can push distantly related species to resemble each other. Again natural selection is a driving force. Bird species that eat flying insects tend to have similar aerodynamic body shapes (even if they aren’t close relatives), kind of like how different kinds of aquatic animals, such as fish and whales, similarly evolved elongated bodies and fins for swimming underwater.

This push and pull of divergent and convergent evolution can make for some surprises when birders dig into the phylogeny (that is, the evolutionary relationships) of some of their favorite birds. Try your hand at guessing which species might be most closely related in the following groupings of birds from your backyard and around the world. Physical resemblances or proximity to one another may be a helpful clue … but then again, maybe not.

Avian Phylogeny: An Evolutionary Tree for Birds

A clade diagram of avian evolution with images of two perched birds with long blue-black bodies and long, curved bills.
Photos from Macaulay Library: Black-billed Woodhoopoe by Ayuwat Jearwattanakanok, Common Scimitarbill by Daniel Engelbrecht.

A phylogeny shows how species are related to one another and displays information about how long ago two or more species shared a common ancestor, revealing the greater patterns at play in evolution.

A clade is a portion of an evolutionary tree in which all the species descend from a common ancestor. In the snippet above from the phylogenetic tree in the order Bucerotiformes, any grouping of species that can be traced in their roots back to a single point form a clade—such as all of the scimitarbills and all of the woodhoopoes, or just Forest and Black Scimitarbills, or just Black-billed and Violet Woodhoopoes. Clades indicate direct lines of evolutionary descent.

DNA Tech Is Making Phylogenies Easier to Construct—and More Accurate

Historically scientists constructed phylogenies of birds by identifying shared physical traits; if two birds had similar beak shapes or vocal organ structures, it was inferred that they were closely related. But those kinds of inferences could be false due to convergent evolution. With the advent of modern genetic analysis techniques in the 1970s and 80s, scientists began looking for shared DNA sequences instead, which proved to be a far more accurate way of determining which birds are close evolutionary relatives. DNA sequencing also provides scientists with thousands of times more data, which means evolutionary comparisons can be conducted at much larger scales—resulting in larger and more accurate phylogenies.

Take the Quiz

Tap or click an image to reveal the answer. (Illustrations are not to scale.)

Who is the closest relative of the Chimney Swift?
Illustration of a gray bird in flight
Illustration of a gray/brown bird in flight
Illustration of a bright green bird with a red neck, long bill, and paler abdomen.
Illustration of a dark brown bird in flight
Who is the closest relative of the Downy Woodpecker?
Downy Woodpecker
Hairy Woodpecker
Lesser Spotted Woodpecker
White-headed Woodpecker
Who is the closest relative of the Peregrine Falcon?
Peregrine Falcon
Illustration of a steel-gray bird with orange and white patterned underside, gray and black stiped tail, gray cap, red eye and a short, sharp bill.
Red-lored Parrot
Who is the closest relative of the Western Tanager?
Illustration pf a bright yellow and black bird with an orange-red head.
Illustration of a red bird with crested head and black mask.
Illustration of a gray and white bird with a red head, with crest, and a conical pale yellow bill
Who is the closest relative of the Eastern Meadowlark?
Illustration of a yellow, black and brown patterned bird with long legs and a black and white striped head.
Illustration of a yellow, brown and black patterned bird with long legs.
Black bird with a brown head and vent, large white bill, yellow under-tail feathers, and two head plumes.
Illustration of a brown/beige and white bird with black and yellow face markings and feathers that look like horns.
Who is the closest relative of the American Goldfinch?
Illustration of yellow bird with a black cap and black and white wings.
Illustration of a yellow bird with a wash of orange on the forehead
Illustration of a gray bird with a yellow head.
Illustration of a red bird with black and white wings and a curved orange bill.
Who is the closest relative of the Kagu?
Illustration of a pale gray bird with an orange bill and legs and a red eye
Illustration of a orange, gray, brown and black patterned bird with a long bill, black and white striped face and red eye
Illustration of a brown and white duck-shaped bird with a white and black striped head and neck, and yellow and black legs and feet.
Illustration of a tall, pale gray and beige bird with a black cap, a turquoise bill and face, and long legs.
Who is the closest relative of the Tawny-crowned Honeyeater?
Illustration of a brown and beige patterned bird with yellow wing feathers, a white underside, orangey cap, thick black stripes across the eye, and a long-black, curved bill.
Illustration of a gray bird with a white and gray patterned underside, cinnamon-colored collar, long, curved bill and a very long tail.
Illustration of a white, gray and black bird with a yellow-orange eye and thin, short black, beak.
Illustration of a dark, brown bird with orange tail feathers, a yellow throat and a red cap and neck.

Phylogeny and Evolutionary Biology

A global map with a yellow-to-green-yo-blue key with blue representing areas with distantly related birds and yellow, areas with closely related birds.
Blue arrow: In areas with stable climates, bird-species composition tends to include a variety of distant relatives. Yellow arrow: In areas with harsh climates, the local groups of bird species tend to be closely related. Map from McTavish et al., used with permission.

Phylogenies can reveal how evolution plays out across space and time. For example, a geographic analysis of bird distributions ranked by their evolutionary relationships reveals that close relatives tend to be clustered together in their own groups in harsh climates and at high elevations (likely because these closely related birds all have traits that allow them to survive where other birds can’t). On the other hand, stable climates seem to support a wider diversity of evolutionary lineages, resulting in communities of birds with more distantly related species.

About the Author

Eliot Miller is an evolutionary biologist who leads the BirdsPlus Index at the American Bird Conservancy. He previously worked at the Cornell Lab of Ornithology, conducting evolutionary ecology research and helping to develop the automated sound identification technology for the Merlin Bird ID app.

The Open Tree of Life Project

Tree of Life logo

The Open Tree of Life is an NSF-funded collaboration among several scientific institutions to create a dynamic, digital, and freely available phylogeny for all of the world’s organisms. Currently led by the University of California Merced and the University of Kansas, the project aims to build a comprehensive and continually updated evolutionary tree that’s posted online so scientists anywhere can easily access it. So far the Open Tree represents 2.4 million species including plants, mammals, amphibians, reptiles, and a complete evolutionary tree of all the world’s birds.

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American Kestrel by Blair Dudeck / Macaulay Library