Birds are warm-blooded vertebrates characterized by feathers, beaks, and the ability to lay hard-shelled eggs, with many species capable of flight. Articles are a unique way for readers to learn about the world around them. In addition to building reading comprehension skills and increasing vocabulary, articles can be used for writing and research. Animals are broken into 6 single-page sections: What Is, Characteristics, Types, Why Important, Fun Facts, and Words to Know.