Zoo-ology: Preen and Clean

April 24, 2011 at 10:02 p.m.
Updated April 23, 2011 at 11:24 p.m.

A sandhill crane stretches its neck to reach the feathers on the underside of its wing during a preening session.

A sandhill crane stretches its neck to reach the feathers on the underside of its wing during a preening session.

By Judie Farnsworth

Feathers - no bird is without them, no other animal has them. Birds spend hours each day preening or grooming their feathers. This is no easy task. There can be up to 25,000 feathers to take care of. Even a tiny hummingbird may have 1,000 feathers.

Preening is not a random activity. Healthy feathers are vital and very methodically cared for. Preening aligns feathers for waterproofing and insulation, keeps feathers aerodynamic in shape, removes parasites and lice, removes tough sheaths from newly molted feathers, creates a healthy image to attract a mate and helps bond as mates preen each other - birds of a feather, and all that.

The outer contour feathers are a complex mesh - rather like Velcro. Parallel barbs attach to the feather shaft or rachis - picture a palm frond with a main shaft and leaves. Many barbules and tiny hooks or barbicels fasten the barbs together.

When barbicels unfasten, a split occurs in the feather. A bird nibbles from the feather base to the tip, essentially zipping everything closed to offer optimum protection.

Try it - if you find a feather. Apply gentle pulling pressure; you'll see resistance before the mesh of the feather splits. Since you're beak-less, you'll need practice, but run two fingernails along the split and voila . you, too, can be zipping with the best of birds. What's more, now you understand why.

Underneath the contour feathers are down feathers that insulate and filoplumes, or sensory feathers. Soft down feathers can be fluffed, trapping air and providing excellent insulation. That's why birds often appear quite roly-poly on a cold day.

A preen gland at the base of the tail in most birds produces waxy oil for waterproofing and conditioning feathers and skin. A bird gathers oil with its beak, then spreads it through its feathers. Some birds, including owls, pigeons, parrots and hawks, lack a preen gland, but have specialized feathers that crumble into powder down that serves the same purpose as preen oil. These birds are less likely to bathe in water and don't need the stronger waterproofing of preen oil. But, before preening, a bird usually exhibits some form of pre-preening activity.

This might be bathing in water, or even dust or dirt. Dust, like powder, can dislodge parasites and absorb sticky plant resins that can then be shaken off.

Have you ever seen a bird on a rooftop or grass that looked totally goofy - with wings spread or one wing lifted and head tilted? The sun is hot and you're sure the bird is drunk or dying? It's sunning; forcing feather mites or parasites to different areas of its body where they can be removed.

Even stranger is the practice of anting. A bird may pick up an ant to rub through its feathers, or even lay on an ant hill. This is thought to distribute formic acid from the ant's body that inhibits parasites that can damage feathers. Millipedes are sometimes used.

Feathers are amazing. The fascination with our natural world is on-going at The Texas Zoo. Keep in touch to grow and know.

Judie Farnsworth is a long time volunteer at the Texas Zoo specializing in educational programs.



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