How does a woodpecker hammer all day without scrambling its brains? There is a sac of fluid just behind its beak that absorbs the shock. In the U.S., woodpeckers must live in forests with both hard and softwoods, such as oak and pine. The bird needs the oaks (or other nut-bearing trees) for food. But it must have softwood in which to hammer holes to cache the nuts. Also, woodpeckers need softwood in which to nest. They are cavity nesters, with young born blind and helpless. A lucky bird finds an existing hole, but others must create their own. Hardwood requires too much effort to peck out a hole big enough. Other nesting species (including mammals) then use the hole the woodpecker created. The acorn woodpecker of Northern California does something no other bird species accomplishes. A family of birds will find a dead, but still standing tree, and establish what ornithologists call a "granary." For up to 30 years, generations of the same family will cache acorns in the tree, sometimes as many as 10,000 at a time. Insects then eat the cached nuts -- providing extra protein for the birds.
