Thursday, 29 July 2010

Feather

There are few things in the natural world more complex and highly evolved than feathers. We take them so much for granted as we see them blowing about in the wind or lining a bird's nest, but they really do demand a closer look. Having found a primary (flight feather) from a House Sparrow (Passer domesticus) on our front garden this morning, I thought it would be good to have a closer look, under the microscope. Here, magnified 10 times, you can see the individual filaments separating along the trailing edge of the feather.
It has been suggested in the past, that feathers developed from reptilian scales - although this theory has been questioned in recent years. Each feather consists of a hollow shaft, quill or calamus, strong and very lightweight, tapering into a rachis as it gets towards the feather tip. From the rachis, there arise the  many, soft barbs which interlock to form the main, vane structure (and the part we normally see). Each barb, is covered with even smaller, hook-like structures called barbules, which aid this interlocking. Birds can often be seen grooming and pulling their feathers through their beaks, this helps to 'zip' the barbs back together to maintain an unbroken surface area.
Feathers are made of the same material which goes to make up the bird's beaks and claws. This keratin protein is much the same thing as makes our finger nails and hair, although in birds, it much tougher.
The ends of these feathers look 'tatty' under the microscope, as they disintegrate into a fine powder which is combed into the feathers to help waterproof them. It is this powder (along with various feather parasites and their droppings) which can be such a problem to some people producing allergic reactions and breathing difficulties.
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