The Origin of Birds and Flight

Theare more than 10,000 species of birds on Earth, each of which possesses its own unique features. Hawks have very sharp eyes, broad wings and pointed talons. Plovers, weighing just a few hundred grams, flap their wings for 88 hours non-stop on the journey of 4,000 kilometers (2,485 miles) that they make every winter, crossing the ocean without mishap.