7.2 Bird Diversity

How are birds different?

Not all birds look the same. They come in all colors and sizes. They live in a variety of habitats. They eat a variety of foods.

Diversity of Birds

About 10,000 bird species belong to 29 different orders within the class Aves. They live and breed on all seven continents. The tropics are home to the greatest biodiversity of birds. The diversity among birds is striking. Birds can vary greatly in size and color. Some fly, some swim, some just walk or run. Some are savage carnivores, others are gentle herbivores. Some are low on the food chain, others are at the top.

Birds live in a variety of different habitats. Birds that live in different habitats will encounter different foods and different predators. Birds can be carnivores (feeding on other animals), herbivores (feeding on plants), or generalists(feeding on a variety of foods). The lifestyle of the bird can affect what it looks like. For example, can you think of some examples of beaks that are adapted to the type of food a bird eats?


The size and shape of the beak is related to the food the bird eats and can vary greatly among different birds. Parrots have down-curved, hooked bills, which are well-adapted for cracking seeds and nuts (Figure below). Hummingbirds, on the other hand, have long, thin, pointed bills, which are adapted for getting the nectar out of flowers (Figure below).

(left) The down-curved, hooked bill of a scarlet macaw, a large colorful parrot. (right) A long, thin and pointed bill of the Swallow-tailed Hummingbird.


Bird feet can also vary greatly among different birds. Some birds, such as gulls and terns, have webbed feet used for swimming or floating (Figure below). Other birds, such as herons, gallinules, and rails, have four long spreading toes, which are adapted for walking delicately in the wetlands (Figure below). You can predict how the beaks and feet of birds will look depending on where they live and what type of food they eat.

(left) The webbed feet of a great black-backed gull. (right) The long spreading toes of an American purple gallinule


  • carnivore: Animal that eats other animals.
  • herbivore: Animal that eats plants or parts of plants, such as seeds.
  • generalist: Animal that feeds on a variety of foods.


  • Birds have beaks adapted for what foods they eat.
  • The feet of birds can be adapted for their specific habitat.


Use the resources below to answer the questions that follow.

  1. How big were velociraptors?
  2. How does the skeleton of a bird compare to the skeleton of a velociraptor? Cite as many examples as you can.
  3. Were birds descended from herbivorous dinosaurs or carnivorous dinosaurs? What evidence leads scientists to this conclusion?
  4. What is the significance of the fossil, “Dave” from China?
  5. Why do the teeth of velociraptors suggest they preyed on animals larger than themselves?
  1. What are the penguins in the video feeding on?
  2. How do penguins store oxygen differently than other birds? How is this related to their lifestyle?
  3. Why do penguins control how much oxygen they carry in their lungs when they dive?
  1. What is the fastest animal on the planet?
  2. How much g-force can a diving raptor experience? How would humans respond to these forces? How does a birds skeleton help them respond to these forces?
  1. Look at the beak of the bearded vulture (Gypaetus barbatus). What is it adapted to do?
  2. Why do bearded vultures wait to feed once they find a carcass?
  3. What unique feeding strategy have these birds developed?
  4. Do you feel the bearded vultures feeding strategy is a learned or innate behavior? Explain your reasoning fully. What do you feel this behavior says about the intelligence of these birds?
  1. What do hummingbirds eat?
  2. Describe how hummingbirds reproduce.


  1. Give two examples of how a bird’s beak is adapted to a specific food source.
  2. Give two examples of how a bird’s feet are adapted to a specific environment.

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