Earth Notes
10:01 pm
Tue December 11, 2007

EarthNotes - Red Crossbills

Flagstaff, AZ – The red crossbill is a bird with a complicated life story. Scientists are just beginning to understand it.

Some parts of the story are simple. True to its name, this large red finch has a crossed bill. Actually, it's the tips of its bill that are crossed like cheap tweezers, all the better to pry open the scales of unripened pine cones and reach its favorite food of pine seeds.

Southwestern crossbills can be found in any mountain forest, but they may be absent for many months, then suddenly arrive in great numbers. True nomads, they spend much of the year wandering vast distances in search of good cone crops. Once they find an abundant supply, crossbills settle down, fatten up, and start breeding. It's a noisy process; listen for their distinctive kip, kip calls as they fly overhead.

As long as seeds are available, crossbills will nest multiple times regardless of season. They'll even nest in winter and early spring, so that parents can start roaming before the next summer begins.

All red crossbills look much the same, but there are actually nine different types that have different calls, eat different seeds, and do not interbreed with one another. Ornithologists know northern Arizona crossbills as type 2, while those in the Chiricahua Mountains have huge bills and are known as type 6.

No one's yet decided whether these types should be classified as separate species. For now, we'll have to keep calling them all simply red crossbills.

-David Lukas