There are more than 9,000 species of birds in the world. More than 400 species have been recorded in Illinois.
Birds are warm-blooded vertebrates.
Like mammals, birds are warm-blooded. This means their body temperature stays the same no matter how hot or cold it is outside. This characteristic allows birds to maintain high levels of energy needed to fly. Contour feathers cover the body of a bird and have a strong, hollow shaft and network of hooks. Down feathers are small and are located under the contour feathers.