Birds are one of the most recognizable groups of animals on Earth — but what exactly makes a bird a bird? In this post, you’ll learn about 8 key traits that all birds share. You will learn about eggs, feathers, wings, beaks, and more. Furthermore, by exploring birds’ traits, you’ll begin to discover how birds are uniquely adapted to survive and thrive in many different habitats across the globe – including on all 7 continents. Get ready to take flight into the amazing world of birds!
For Teachers: If you’re an educator planning to teach kids about birds, you may enjoy using my complete Bird Unit. The unit is packed with all the handouts, worksheets, activities, and science diagrams you will need for teaching kids ornithology, aka “bird science”. You can also bundle and save with my Bird Bundle or my Vertebrate Groups Bundle. I think you and your students will love these materials (plus you’ll support my blog with your purchase! ❤️)
What are birds?
Before we dive into the traits of birds, it helps to answer the question “What are birds?” Birds are one of the groups of vertebrate animals. The other vertebrate groups are amphibians, reptiles, mammals, and three types of fish. Birds share a common ancestor, meaning they are all part of the same evolutionary family tree. If you traced that family tree back far enough, you’d discover that birds evolved from theropod dinosaurs! Because of this shared ancestry, a sparrow is actually more closely related to a dinosaur than to a mammal, amphibian, or any other living vertebrate class.
Scientists use these evolutionary relationships to decide which animals belong in the bird group. Because of this shared ancestry, all birds share a few key traits. In this post, we’ll dive into those traits and discover what makes birds unique!
A Backbone
Like all vertebrates, birds have a backbone, also known as a “spine”. Since you are also a vertebrate, you have a backbone too! A backbone is actually made of many individual, smaller bones called vertebrae, all stacked up in a flexible column. Birds’ spines help us tell them apart from invertebrate (backbone-less) creatures like insects and mollusks.
Lungs
Birds breathe air through lungs. This sets them apart from fish, who breathe through gills, and some amphibians that breathe through their skin, or some combination of skin, lungs, and gills. Even birds that dive underwater, like ducks, penguins, and puffins, must return to the surface to breathe air.
While a human might be able to hold their breath for about a minute, some seabirds can hold their breath for much longer. For example, a penguin can hold its breath for up to twenty minutes! However, if they cannot get to the surface to breathe for some reason, a penguin (or any bird) can drown. They do not have gills like fish and sharks.
Warm Blooded
Birds are warm-blooded (also known as endothermic), which means they make their own body heat and maintain a constant temperature. Birds are not the only vertebrates that are warm-blooded. Mammals and even some fish are warm-blooded too.
You may be wondering: what does it mean to be warm-blooded? Warm-blooded animals make enough body heat to keep a relatively constant body temperature. For example, most humans maintain a constant body temperature of around 98°F (37°C). This takes a lot of energy, which comes from eating food. Many warm-blooded animals also have thick fur or feathers to help insulate their body – the same way a thick sweater keeps you warm by trapping your body heat.
Lay Eggs
Baby birds hatch from eggs. Inside an egg, a chick develops while protected by a hard eggshell. The unborn chick is nourished by a yolk, which provides food as it grows.
Most birds lay their eggs in nests, which they build in trees, on the ground, on cliffs, or even on buildings. Nests come in several shapes and sizes, from tiny woven cups made of dried grass to huge platforms constructed from sticks. Parent birds sit on the nest to keep the eggs warm, an act called incubation.
If you want to learn more about bird eggs and baby birds, read my post about the bird life cycle or my post about what’s inside of a bird egg.
Wings
Birds have wings. Wings allow many birds to fly, sometimes covering great distances and sometimes reaching great speeds. For example, the Arctic tern migrates all the way from the Arctic to Antarctica. A peregrine falcon can reach a speed of 200 mph while diving after prey!
However, not all birds can fly. Examples of flightless birds include ostriches and penguins. These birds still have wings, but they use them for other purposes. For example, an ostrich uses its wings to help it balance while walking or running. A penguin uses its fin-like wings to swim – essentially, to “fly” underwater!
Read more about types of bird wings and their functions.
Feathers
All birds have something that no other vertebrate group has: feathers. In fact, no other living animal has feathers. Feathers cover the bodies of birds. They help them regulate their body temperature in both hot and cold environments. Some use their molted feathers to line their nests and keep their babies comfortable and warm. The wings of birds are covered in specialized flight feathers. These flight feathers develop as a baby bird grows up.
Bird feathers come in many different sizes and colors. An extreme example is a peacock’s tail with its long, showy, bright blue feathers. Some birds, like the peacock, may use their feathers or “plumage” to help attract a mate. Sometimes, male and female birds have different colors or shapes of feathers. This is an example of something scientists call “sexual dimorphism,” which means the male and female of the same species look quite different from one another.
A Bill
Birds don’t have mouths full of teeth like you or me. Instead, they have a bill. All birds have a bill, also called a beak. Bird bills help birds find and eat their food. Birds also use their bills to preen their feathers, build nests, and feed their young.
Beaks come in many different shapes and sizes. Some bills are long and pointy for probing into sand or mud to catch worms and snails–like an egret’s or sandpiper’s. Some bills are sharp and hooked for catching and eating prey like mice or fish–like a hawk’s or cormorant’s. Other bills are small and strong for cracking open nuts and seeds–like a cardinal’s. The special shapes and sizes of bills are an example of an animal adaptation: a physical trait or behavior that helps an organism survive in its environment.
If you are an educator and you want to teach kids about animal adaptations or bird beaks, I highly recommend trying my bird beaks lab activity. It’s a hilarious and hands-on way to see how different beak shapes help birds eat different food sources.
Scute-covered Feet
You might be wondering: what is a scute? In a lot of ways, scutes are very similar to scales. You may already be familiar with scales, which cover the bodies of snakes, lizards, and some fish. Scutes are thicker than scales and don’t overlap the way scales do.
A scute is a thick, armored plate found in the legs and feet of birds. Birds are not the only animals with scutes. Scutes also make up the rough-textured surface of crocodile and alligator skin and the shells of turtles.
Study birds with Wild Earth Lab!
There’s no need to scramble to put together the perfect lessons on birds – I’ve already created them for you! The Bird Unit includes all the printable materials you need for studying bird life cycles, eggs, bird anatomy, adaptations, and more! You can also find the Bird Unit within my even more comprehensive Bird Bundle, which includes individual units on seabirds and shorebirds, freshwater birds, and birds of prey! If you’re studying all 5 Vertebrate Groups, then I recommend my Vertebrates Bundle, which includes 5 units on birds, fish, reptiles, amphibians, and mammals.
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Vertebrates Bundle: 5 units on amphibians, birds, fish, mammals, reptiles
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Read more about birds…
If you enjoyed this post about bird traits, I think you’ll love reading these posts too:
- Read this guide to the bird life cycle
- Use this classroom activity guide for a Bird Beaks Lab to learn about animal adaptations
- A list of 8 Bird Learning Activities for kids
- Learn what’s inside an egg?
- Learn about the types of Sea and Shorebirds you can spot at the beach
- Read about the types and functions of Bird Wings
- Read about the key traits of birds of prey
Find your next topic from Wild Earth Lab:
If you enjoyed this post, I know you will love trying my other science and nature units in your classroom too!
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References and Further Reading
- Clark, M., Douglas, M., Choi, J. (2018). Biology 2e. Open Stax. Ch. 29. Available: https://openstax.org/books/biology-2e/pages/29-5-birds
- John Moore Museum (2024). Peregrine Falcon: The World’s Fastest Bird. Available: https://www.johnmooremuseum.org/peregrine-falcon-the-worlds-fastest-bird/
- Reeves, N., et al. (2013). Concepts in Biology. Open Stax. Ch. 15.6. Available: https://openstax.org/books/concepts-biology/pages/15-6-vertebrates
- Worley, K. (2016). Avian Eggs. San Diego Zoo. Available: https://sandiegozoowildlifealliance.org/story-hub/zoonooz/avian-eggs