Why most woodpeckers are black and white

• The contrasting black and white pattern found on the backs of many woodpeckers helps to conceal them from predators. Known as disruptive coloration, this sharp contrast in colors helps to break-up and conceal the shape and outline of a woodpecker as it climbs the side of a tree.
• Considering the pounding it takes, why doesn't a woodpecker's bill wear down to a ragged nub? Wear down it does, but special cells on the end of the bill are constantly replacing the lost material. This keeps the chisel-pointed bill strong and resilient, while actually allowing it to be sharpened with every blow.
• A woodpecker's pointed tail feathers are especially strong and rigid. The tail bone, lower vertebrae and the tail's supporting muscles are also large in comparison to other birds. These modifications allow a woodpecker's tail to serve as a prop that supports their weight as they climb and cling to trees.
• The barbed tip of a woodpecker's tongue is very sensitive to touch and can both detect and impale insect larvae. The tongue is coated with sticky mucus that is secreted by large salivary glands; this coating helps to ensure that its prey does not slip away.
• Most woodpeckers' tongues are two to three times longer than their bills. The base of some woodpeckers' long, retractable tongues reach entirely around the back and top of the skull and end behind the right eye socket.
• To prevent small bits of debris from entering their nostrils while excavating trees, woodpeckers have tufts of stiff feathers growing over both nostrils. Woodpeckers also have a third eyelid to help protect their eyes from debris while drilling into trees.
• While excavating a cavity, a woodpecker's head can strike a tree's surface at speeds up to 13- 15 miles per hour and do it at over 100 strokes per minute. This is equivalent to a person crashing head-first into a tree while running at top speed.
• In order for woodpeckers to survive the 10Gs of force that they can sustain with every blow against a tree, they have the following special adaptations:

-The bones between the beak and the skull are joined by a flexible cartilage which cushions the shock of each blow.
-The skull is made of spongy, air-filled bone and the brain is packed very tightly into the brain cavity with little room to rattle around during impacts.
-The shear force from each blow is directed not to the brain, but downward towards very strong neck muscles that act as shock absorbers.
- A woodpecker's head and body are always in a perfectly straight alignment when hitting a tree to avoid breaking its neck.

• To help distinguish the difference between a Hairy and a Downy Woodpecker visiting your feeders, look for the Hairy's chisel-like bill which is much longer than the Downy, which often equals the width of the rest of the head. The Downy's head is twice as wide as its very short bill.

source: http://www.wbu.com/botm/botm_0712.html