Earth Notes
4:04 am
Wed December 24, 2008

Earth Notes - Mistletoe and Birds

Flagstaff, AZ – Earth Notes: Mistletoes and Birds


During the holidays, sprigs of mistletoe are bits of nature brought indoors. We know them as places for one particular human ritual, but in the natural world mistletoes play other important, and often overlooked, ecological roles.

In the Southwest, the common big-leaf mistletoe grows in large clumps among the upper branches of willows, cottonwoods and sycamores. It provides a steady and dependable supply of berries for birds like waxwings, bluebirds, and robins.

Birds are perfect vehicles for transporting mistletoe seeds to new locations. Full of berries, they love to sit on top of sun-warmed branches while digesting their meals. When digestion is done, the seeds are left in ideal settings they could never reach by themselves.

Mistletoes are parasites that don't need their own soil. When their seeds germinate, they send out roots that penetrate the bark and start taking carbon, water, and nitrogen from their host. Over the course of many decades, a mistletoe plant may grow into a sizable clump and produce huge numbers of berries.

It's easy to see how mistletoes benefit bird populations, but harder to see how they benefit trees. In fact, many people attempt to remove them without realizing that mistletoes and trees have beneficially co-existed for nearly 20 million years.

Mistletoes drive ecological and evolutionary change by opening up wooded areas and pruning the gene pool of their host species. Plus, they provide little splashes of green ornamentation among winter's bare branches a reminder that spring will be back someday.

Happy holidays from all of us here at Earth Notes.

-David Lukas