BirdÂ Coloring Pages
Modern birds are characterized by feathers, a beak with no teeth, the layingÂ of hard-shelledÂ eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. All birds have wings, which are evolvedÂ forelimbs, and most can fly, with some exceptions including ratites, penguins, and a number of diverse endemic island species. Birds also have unique digestive and respiratory systems that are highly adapted for flight.
Some birds, especially corvids and parrots, are among the most intelligent animal species; a number of bird species have been observed manufacturing and using tools, and many social species exhibit cultural transmission of knowledge across generations.