Big woodpeckers trash others' homes.

Woodpecker biologist Daniel Saenz now has the data to show that frustrated scientists aren't imagining things. Pileated woodpeckers really are attracted to the homes of red-cockaded woodpeckers.

Saenz of the Wildlife Habitat Laboratory in Nacogdoches, Texas, frets over the cavities that the small, endangered red-cockaded woodpeckers peck out of healthy pine trees. The 8-inch-long birds routinely spend 6 years excavating before a cavity reaches the right size. A finished cavity houses a single bird.

The pileated woodpeckers, like most of the clan, usually whack their cavities out of dead trees in which a fungus has already softened the wood. However, Saenz and other biologists have seen pileated woodpeckers start slamming away at the painstakingly excavated red-cockaded cavities, making the openings too large for the original owners to tolerate when the invader abandons the task. The 16-inch-high birds "can ruin years of work in one afternoon," laments Richard Conner, also from the Texas lab.

Saenz's study confirms that the smaller birds' nesting trees attract pileated woodpeckers. In Texas' Angelina National Forest, his team compared 827 trees with red-cockaded cavities to 110 uninhabited pines. The researchers found 5 percent of excavated trees attacked but none of the others.

Pines growing amid sprouting hardwoods seemed more appealing habitat to pileated woodpeckers than did pines with little brush below. Saenz counts the observation as yet another reason to insist that forest managers stick to the program of burning out brush to protect red-cockaded habitat.