few days ago I was out in the yard when I heard a bird scratching on a pine tree, intermittently rapping as it scuffled upward.

It could have been any one of the local trunk-treading bark-borers -- creepers, nuthatches, chickadees, etc. But when it swung into sight, its predominantly black-and-white markings, combined with a jaunty red spot on the back of its head, revealed it to be a woodpecker.

Twenty-two members of the family Picidae in five genera regularly occur north of the Mexican border (23 if you include the possibly extinct ivory-billed woodpecker). At least 12 species have been found in Colorado, and nine in Boulder County.

The group is known for intriguing adaptations and behavior traits, as well as a few oddly

A male downy woodpecker hops up a tree in search of food.
named species. The word "woodpecker" is a bit unusual in itself, but modifiers such as ladder-backed (referring to horizontal bars on the bird) and pileated (meaning crested) can be puzzling.

Some woodpeckers are named after features that are rarely visible in the field, such as red-cockaded and red-bellied. Others are named for more prominent physical markings, such as red-headed -- the species that most closely resembles movie star Woody Woodpecker -- white-headed and black-backed. Still others get their monikers from their discoverers, such as Lewis`s woodpecker, named after Meriwether Lewis of the Lewis and Clark expedition.

Then there`s that favorite of comedy writers: yellow-bellied sapsucker. A few yellow-bellies visit Colorado in winter, but Boulder County`s two breeding sapsuckers are Williamson`s and red-naped. Male Williamson`s sapsuckers (mainly black with white, red and yellow highlights) and females (brownish and finely barred overall) look so different that at one time they were thought to be separate species. Sapsuckers get their name from their habit of poking holes and stripping bark to promote sap flow on trees and bushes, and lapping up what oozes out.

The bird in my yard was a downy woodpecker, a species that is NOT downy, except for a tuft of feathers on its beak that keeps wood chips and sawdust out of its nostrils. The downy`s slightly larger and longer-billed look-alike -- hairy woodpecker -- is sleek and NOT hairy at all. Downies are one of two species commonly found in urban settings in Colorado, the other being northern flicker.

[1] Woodpeckers hack into trees for several reasons: to excavate nesting and roosting holes, to announce territories and to find something to eat. The degree of drilling varies according to the birds` size and feeding preferences. Crow-sized pileateds, which are not found in Colorado, chisel out cavities the size of a breadbox in pursuit of carpenter ants. Conversely, downies -- our smallest woodpecker -- target twigs and light fare such as cattail stalks. Others, notably Lewis`s and red-headed woodpeckers, get many of their meals by pursuing flying insects and do little pecking.

Why don`t the bark-bashers get concussions? They are protected by several structural features, such as spongy skull bones. They have tiny brains, which lowers surface-to-area volume and disseminates force in the skull. The birds also peck in a straight line, preventing sideways torque and resultant tearing.

Other adaptations help woodpeckers with their tree-trekking lifestyle. They have powerful neck muscles, stiff tail feathers help the birds prop up against trunks, and zygodactyl toes (opposing pairs, two facing forward and two backward) facilitate vertical clinging.

Woodpeckers` tongues are awesome, and it`s mind-boggling to imagine the evolutionary process that produced them. They are long, barbed at the tip and sticky. Their anchor points (hyoid apparatus) have migrated up and around their skulls. The basal supports may be in the crown of the head, or as far as the upper bill mandible or around the eye socket. This allows some woodpeckers to stick out their tongues 5 inches to snare deep-dwelling prey.

Woodpeckers aren`t the only creatures to benefit from woodpecker adaptations. The cavities they carve provide homes for a multitude of birds such as bluebirds, swallows, wrens and owls, and mammals such as flying squirrels. Warblers and hummingbirds will gladly sip at the "wells" created by sapsuckers, and one woodpecker might even prove beneficial for Coloradans.

Large tracts of conifers in the state have been attacked by bark beetles. The three-toed woodpecker (yes, it has only one toe in the rear) lives in evergreen forests around the globe in the Northern Hemisphere and reaches the southern terminus of its distribution in Colorado.

Three-toeds are attracted to trees that have been killed by fire or disease, and gladly gulp down beetles living in the dead wood. They can be found in Boulder County burn areas and in Wild Basin in Rocky Mountain National Park. It`s not likely that woodpeckers alone can control the destructive burrowing beetles, but we should welcome any help we get.