Flight has been a fascination for humans for thousands of years, and although we are able to fly in aeroplanes, helicopters, microlights etc, we haven’t quite mastered the art of human powered flight. The idea of being able to soar through the air as effortless as a bird is that of just a dream, as unlike birds we are just simply not adapted for it. Birds have a unique set of adaptions that enable them to take to the skies.
It is thought that birds feathers have evolved from scales which may have been used by their non-aerial reptilian ancestors for insulation. With feathers being lighter than scales as well as being strong and flexible they make for highly efficient flying gear.
Just as we have different clothes for different parts of our bodies, so too do birds have different feathers for different parts of their bodies. There are flight feathers which are found on the wings and tail which aid in well, flight. Contour feathers which cover the body and help with insulation and protection of the bird. Down feathers that lie under the contour feathers and trap air to keep the bird warm. And filoplumes which are tiny hair-like feathers that are thought to detect vibrations and movement.
Compared to mammal bones which are filled with marrow, birds bones are much lighter as they are hollow and are supported by a network of internal struts. The finger bones are reduced and fused together as well as the number of bones in the tail are reduced, altogether this makes the skeleton more rigid which means that there will be less need for the many muscles and tendons to hold the skeleton together, allowing for more advanced muscle power for the wings. There are two sets of muscles attached to an enlarged breast bone that are used to pull the wing up and down which as you can imagine will play a vital part in flying.
One of the reasons we see certain birds in certain areas is because of their diet, and this also happens to be an adaption for flight. The food that eat are mostly high in usable calories so that the are able to get as many calories from the small amount of food that they eat, such as seeds, fruits and meat. Their bills have also evolved by not having teeth or powerful jaws which will make them a lot heavier, but are still strong and flexible as they are made of the protein keratin.
The adaption that I personally find most fascinating is their unique breathing system that ensures that they acquire the large amount of oxygen needed to sustain flight. They have specialized air sacs that will store inhaled air that has passed through the lungs, then it will be sent back through the lungs again to increase the opportunity for capturing oxygen (this is a simplified version). The air going through the lungs twice ensures that the oxygen is received both with the inhale and the exhale meaning that they are able to benefit far more from each breath.
Together all these adaptions make the bird light, streamlined and strong enough to be able to overcome gravity and continue to trigger our imaginations and keep us wondering what it would be like to truly fly like a bird.