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. The purpose of these feathers is to insulate the bird from the cold. The hard shell keeps an egg from drying out and allows parents to sit on the eggs during incubation. Even though bird eggs are hard-shelled, they have microscopic pores which allow oxygen to pass into and carbon dioxide to exit the shell. Eggs come in a variety of colors, patterns, shapes and textures.