Touch Heart and Blood Lungs and Breath Brain and Nerves Eyes and Sight Ears and Hearing Noses and Smell Introduction Birds are different to most mammals in a number of immediately obvious ways, they walk on two legs and have two wings, they have feathers instead of hair and a beak instead of jaws with teeth. The are also similar to us in some ways, they are warm blooded with a normal body temperature of around 40C, several degrees warmer than most mammals, they also have two eyes and two ears, though these are not normally visible.
Most birds have little or no sense of smell.
Birds have also had to evolve a compact body shape in order to facilitate flying. All the major skeletal differences between birds and their reptilian ancestors are a response to the requirements for flight. All birds have the same basic plan, though different life styles have meant that they have evolved different variations on the central theme. Birds such as swans have more vertebrae in their necks than those like parrots who have very short necks. Swans have 25 vertebrae, parrots have 9.