Birds are some of natures most beautiful creatures.  They have been on earth for 150 million years.  Most of them fly, except for a few ones that are too large and heavy (like ostriches).  Today, there are 10,000 species of birds.  There are three dietary groups: carnivores, herbivores, and omnivores.  Carnivores (like eagles) eat other animals.  Herbivores (like cassowaries) eat only plants.  Omnivores (like bluebirds) eat both plants and meat.