The lungs of birds are uniquely designed for flight. They do not operate like the lungs of mammals and reptiles as “bellows” which fill when we inhale and empty when we exhale. Instead, they have two airsacs (one in front of the lungs and one behind the lungs) which push oxygenated air into the lungs during both inhalation and exhalation. This is very important to birds for two reasons. First, birds are able to breathe normally while flying into the wind. Second, flying uses huge amounts of energy and oxygen so this ensures that the bird has highly oxygenated blood at all times. Dr. Michael Denton, a molecular biologist and NOT a creationist, wrote a book titled, Evolution: a Theory in Crisis. In it, he offered the incredible design of the bird lung as a challenge to life evolving gradually over millions of years. On another interesting note, bats also fly in the air. They are even heavier than birds, but they possess bellows-type lungs like all other mammals. They seem to get along just fine. If bird lungs are so much more efficient, why would nature not “select” the better system? Isn’t that what Darwinism and natural selection are all about? And it is difficult to imagine how a bellows-type lung could slowly change into the vastly different bird-type system while still remaining completely functional at every developmental stage. Otherwise, the creature would stop breathing and die. It seems more logical to conclude that both kinds of lung exist because they were designed perfectly for each kind of creature by the Grand Designer of the universe—God.
“Blown away by design: Michael Denton and birds’ lungs” Creation 21(4):14–15; September 1999