subject: The Reason Birds Can Fly [print this page] No doubt many bird lovers will be surprised to find out that many birds in the wild prefer to be on the ground, rather than the sky. And, in regions of the world where they are not threatened by predators, they actually spend most of their time on the ground.
As a matter of fact, if you go to places around the globe where birds have had no serious predators for centuries, you will very often find that some of the birds have evolved to where they either have no wings or they have wings that are almost useless in flight. This is because they no longer need the ability to fly to escape danger.
Because of this, they feel extremely at ease simply remaining on on the ground. After all, this is where they find most of their food. A perfect example of this is the well known ostrich which, over the years, has lost the ability to fly.
Today, among experts, it is widely accepted that dinosaurs are the ancestors of today's birds. Originally, smaller sized dinosaurs lived on the ground. Here they were at a disadvantage as they were forced to compete for food and survival over their larger cousins. Most of these smaller dinosaurs could not compete effectively and died out.
But others did survive. They evolved. Over the centuries they evolved wings. And with the wings came both the ability to effectively escape larger predators and to find easier sources of food where their larger brethren could not go. The acquisition of flight is what enabled many of these smaller dinosaurs to survive.
Over the centuries, birds have evolved certain evolutionary traits that allowed them to fly whereas mammals did not evolve these traits. One of them is that birds are almost always lighter in weight than comparatively sized mammals. If you were to compare just about any bird to a similarly sized earthbound mammal, you will discover that it probably weighs from two to four times less than the mammal. This is primarily due to its skeletal system which usually consists of hollow bones. The hollow bones are supported by internal struts which make them amazingly powerful.
Not only that, but a very large part of an average bird's body consists of air. Birds possess air sacs all through their bodies which, in addition to being great weight saving devices, allow them to utilize oxygen many times more efficiently than most mammals can.
Although, through the centuries, birds have evolved with many other weight saving features, for the most part, it is this lightness of weight that enables them to easily launch themselves into the air and stay aloft.
And, lastly, we come to the winds. Wings that have improved through evolution to be the perfect constructs that enable then to easily glide through the air with little or no turbulence.
