Reptile or Bird? Easy to Tell, Even in the Shell

As we continue our tour of the vertebrates in the Kingdom of Animals, we will catch a ride on a robin to visit the reptiles and the birds. (or perhaps we’ll just hop on the back of an ostrich – we don’t have so far to go) Reptiles range from slithering snakes to basking lizards to snapping crocodiles to armored tortoises; there are even some reptiles known worm snakes which look like half-foot-long scaly worms. Reptiles are most recognizable because of their dry skin that is covered with thick scales or horny plates.

Reptiles are found in many parts of the world, from tiny geckos living on the islands of the Caribbean to the enormous saltwater crocodiles of Australia. You will find huge leatherback sea turtles 3,000 ft (1,000 m) below the sea and tiny draco lizards gliding from tree to tree in the Malaysian rainforest. In your own backyard, you might find some skinks or garter snakes if you’re lucky (or a Gila monster and rattlesnake if you are less lucky). Despite being so widespread, reptiles are almost never found in very cold regions because they, like amphibians and fish, are cold-blooded.

Birds, on the other hand, are warm-blooded, their bodies maintain the same temperature regardless of the temperature around them. This feature, along with the birds’ lovely feathers, allows them to live in even the coldest climates that are inhospitable to reptiles and amphibians. There are snowy owls near the North Pole, gentoo penguins in Antarctica, long tailed quetzals near the equator, and birds of all shapes and sizes in between. There are bar headed geese that can fly in the thin air over the Himalayan mountains and emperor penguins that can dive over 1,700 ft (500 m) under the ocean.

Birds are quite easy to tell from other animals because they are the only type with feathers. They all have two legs (often covered with tough, scaly skin) and wings (although some birds, such as penguins and emus, cannot fly). Birds also do not have a mouth with teeth like most other land animals, but instead have a beak or bill which varies in shape depending on what type of food they eat. There are around 40 types of birds (with around 10,000 species!), ranging from woodpeckers to warblers and cuckoos to cranes. There are even several types that are domesticated, meaning they have been tamed by humans, such as chickens, turkeys, and geese that you might see on the farm, as well as pet parakeets and macaws.

There is a funny little book called Flap Your Wings by P.D. Eastman where a little boy finds an alligator egg on the ground, and mistaking it for a bird’s egg, puts it into a nearby nest. The new mother and father work themselves to the bone to feed their growing baby, only to figure out later that he belonged in the nearby pond the whole time! This distress might have been averted if the boy (and the birds) had known the simple trick to tell a reptile’s egg from a bird’s. Bird eggs are ovoid in shape, meaning that they are tapered at one end. Crocodile eggs, on the other hand, are oval in shape, the same thickness at both ends. Turtle and snake eggs are often round, as well, with a soft, leathery shell. A few reptiles are even born live from their mothers, while birds all lay eggs. Both birds and reptiles are born looking like a small (although sometimes ugly) version of its parents, unlike amphibians that change shape as they grow.