How many feathers do birds have

A. The answer depends upon what type of feather you're talking about: birds have lots more feathers than the ones you can see.

Generally speaking the bigger the bird the greater the number of feathers: large species such as swans can have 25,000 feathers in total, whereas the hummingbird has as few as a hundred.

Q. What types of feathers do birds have

A. There are three main types.

Next to the skin are the downy feathers, which keep the body warm. Down plumage is soft and fluffy and some birds have more than others: baby birds are all down and the adult waterfowl has more down than any other bird, to keep it warm whatever the temperature of the water.

Next are the contour feathers, which cover all the external areas and overlap each other, carrying out many essential jobs: keeping heat in, water out and providing a streamline profile for flying.

The last important type of feather are those found in the wing and tail, which are the longest, stiffest and strongest, creating and maintaining flight.

Q. How are flight feathers designed for strength

A. The vanes, the flat part of the feather, are arranged along the hollow shaft, in a similar way to the teeth of a zip. Birds preen themselves by running their beaks along the feather, re-sorting the separated vanes back into a unbroken blade.

Q. How do birds waterproof their feathers

A. Different birds get around this important problem in different ways.

Some species have a preen gland that coats them in a resin, keeping them waterproofed or buoyant. Others produce feathers with talc that when preened through the coat provides a waterproof dressing.

Q. Do birds moult

A. Yes, and for some birds, notably those that migrate long distances, when and how long moulting takes place is crucial.

Most birds replace their hard working feathers gradually and at the end of a migration so that they're always able to fly. Although some birds shed all their flight feathers at once, leaving them grounded for weeks.

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by Lisa Cardy