BIRDS UNIQUE FEATHERS

Feathers are one of the most prominent features of a bird's anatomy, and they are unique to birds. Every bird has feathers and everything that has feathers is a bird. Feathers perform a number of functions for a bird. Firstly, they provide insulation, this is very important in a warm blooded animal (body temperature of most birds is maintained at around 40C). It is believed by most scientists that this insulating effect was the primary force driving the evolution of feathers, ancestral birds developed feathers to keep themselves warm. Feathers also protect birds from UV light.

Secondly, feathers allow for flight. Scientists believe that flight evolved in birds as a result of their possessing basic feathers and that this added selective pressure to the evolution of feathers making them larger, stronger and refining their structure.
Thirdly, feathers control what a bird looks like. A plucked chicken or pigeon looks very different to a fully feathered one. Feathers supply the bird with colours allowing for camouflage and secondary sexual characteristics and sexual display. Consider the tail feathers of a peacock.

Feathers have a basic form of a central hollow supporting shaft called a 'rachis' and a number of fine side branches. These side branches have even finer sub-branches in contour feathers. The side branches in these are called barbs and are linked together by a set of barbules. The base of the feather - where there are no side branches - is called the calamus or quill and at the base of this is the hollow entrance that was used by blood veins to carry nutrients to the growing feather when it was alive.

A bird has many different sorts of feathers which perform different jobs.
The largest feathers are contour feathers. These give the bird its shape and colour and include both the flight feathers, called remiges, and the tail feathers called retrices.
The rest of the feathers you see when looking at a bird are the ordinary body 'contour feathers'. These give the bird its characteristic smooth round shape. They also give the bird its visual colouring and provide a first level of defence against physical objects, sunlight, wind and rain. They are very important.











The next most important feathers on a bird are the down feathers. These are smaller and lack the barbules and their accompanying hooklets so they are not zipped together and do not look so neat. In fact hey are soft and fluffy. They provide most of the insulation and are so good at this that mankind for many years used to collect the 'down' from various birds to put into sleeping bags and eiderdowns to help keep us warm at night.