Feathers, flyways and fast food
Original by Dr Margaret Rowe, 2002
Last revised by the Department of the Environment and Heritage, December 2004
ISBN 0 6425 4820 X
The feather coat
Figure 2a A down feather
- Insulation–helps keep an even body temperature (not too hot and not too cold)
- Feathers are very important for flight
- The colours are useful for camouflage and sometimes for communication
- In various situations, feathers also repel water and assist in swimming, hearing, protection and cleanliness.
A typical feather from the main body or wing consists of a central shaft with a vane on either side.The vanes are made up of barbs that are held together with tiny hooks. As the bird preens, these tiny hooks grip the barbs, keeping the feathers in good condition.
Find a feather and look at it with a magnifying glass or microscope.
Figure 2b Contour feathers
The main flight feathers of the wings are large and stiff. The outer ten flight feathers on each wing are called primaries. They are attached to the section of the forelimb of the bird that is the equivalent, in bone structure, of the human hand. The inner flight feathers of the wing, the secondaries, are attached to the ulna bone of the forelimb of the bird, the equivalent of the human forearm. There are usually 12 flight feathers in the tail, attached to a tail bone. Amongst these main flight feathers are many overlapping smaller feathers, called coverts.
These tiny feathers are soft and fluffy.They provide a thick cover under the larger, stiffer main body feathers and on the front of the bird.
Figure 2c A main flight feather
Figure 3 Comparison of bird wing with the human arm
Birds preen their feathers frequently, arranging them and drawing them through their bills.They groom their head and neck feathers by scratching them with their feet. A rich oil of waxes, fats and water from the preening gland on the rump of the bird is wiped over the feathers.This keeps them flexible and waterproof, protecting them from bacteria and fungi.
Feathers fade and wear over time and are replaced regularly. Moulting occurs as new feathers grow and push the old ones out. Primary feathers are usually replaced yearly, while secondary feathers are likely to be replaced twice a year.
In most birds, primary wing feathers are replaced in sequence, one at a time. Only small gaps are present at any one time, so the bird is always able to fly. Ducks and swans are an exception to this; they are unable to fly during the moult of their wing feathers.
Feather colour is due to coloured pigments, called biochromes, or to special features of the surface of the feathers which create their effect by scattering and reflecting light.
The patterns and colour of birds assist their survival in some way. Sometimes the patterning on the bird, and its eggs and chicks, blends in with the surrounding landscape. For example, the nest of many shorebirds is nothing more than a shallow depression, like a saucer, in the sand or gravel. The eggs and the newly hatched chicks are pale buff, speckled with brown. They are very difficult to see against the background of sand and pebbles.
The parent bird has irregular bands of colours such as brown, grey, black and white across its head, neck, breast and back. These bands of contrasting colours break up the outline of the bird very effectively, and blend with the horizontal lines of the shoreline and the horizon.The bird is not easily detected against the background.
Many shorebirds have a dark upper surface and are pale underneath.This also disguises by disrupting the outline of the bird. The white undersides of shorebirds reflect the colour of the sand or mud. Shorebirds with long legs cannot rely on this reflected colour and they are usually darker underneath.
Shorebirds are usually well camouflaged, but the colours and patterns of their plumage probably also assist in recognition of each other and of a suitable mate.
Obtain an illustrated handbook of birds:
- Look at coloured pictures of some of the Plovers found on our beaches.
Can you see the bands of colour that make it hard to see the bird when on the beach?
What colours are they?
- Look at coloured pictures of some of the sandpipers and stints. They are mainly, grey-brown and white when visiting Australia. They moult into breeding plumage, a more reddish-brown colour, before reaching the tundra regions during the Arctic summer.
Make an educated guess, by looking at the colours of the breeding plumage, to work out what colours provide good camouflage in the vegetation of the tundra?