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Great Blue Heron

Great Blue Heron
(Courtesy NEBRASKAland Magazine/NGPC)

You can tell a great deal about a bird just by looking at its wings. The size and shape of a bird's wings will affect its ability to fly, migrate, hover, dive, and even soar for days.

The wing size and shape will also affect how fast a bird can fly, how well it can maneuver, and how much energy it must expend to fly.

The wing of a bird is much like the arm and hand of a human. The inner wing consists of two sections similar to the human upper arm and forearm. The lower wing is like the hand of a human, with numerous smaller bones.

Flying birds have very large breast muscles. In fact, these muscles are approximately one third the total body weight of the bird! The large breast muscles are attached to a large bone called the keel. The keel extends from the sternum (breastbone) down along the chest and stomach.

This all sounds good, right? Big muscles and strong bones enable birds to fly! But a problem arises because of the way muscles work. A muscle works by contracting or becoming shorter. To fly, the bird needs to pull its wings up and down. You'd think a bird would need a muscle on the top of the wing to pull the wing up and a muscle on the bottom to pull the wing back down.

But if we look at the anatomy of a bird's skeleton, this arrangement isn't workable. There just isn't enough room on the top of the bird's skeleton to attach a muscle.

To solve this problem, birds have developed an amazing pulley system: a muscle on the bottom of the bird (on its chest) actually pulls the wing down as well as up!


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