Pets and Animals World

Birds are characterized as warm-blooded, vertebrate animals primarily having feathers, forelimbs modified as wings, and hollow bones. Birds range in size from the tiny hummingbirds to the huge Ostrich. Most birds are active during the day, but some birds, such as the owls and nightjars, are nocturnal and active during twilight hours. Many characteristics and behaviors of birds are distinct from all other animals, but there are some similarities.