Chickadees, nuthatches and warblers foraging their way through forests have been shown to spur the growth of pine trees in the West by as much as one-third, according to a new University of Colorado at Boulder study.
The study showed birds removed various species of beetles, caterpillars, ants and aphids from tree branches, increasing the vigor of the trees, said study author Kailen Mooney. Mooney, who conducted the study as part of his doctoral research in CU-Boulder's ecology and evolutionary biology department, said it is the first study to demonstrate that birds can affect the growth of conifers.
"In a nutshell, the study shows that the presence of these birds in pine forests increased the growth of the trees by helping to rid them of damaging insects," said Mooney. "From the standpoint of the trees, it appears that the old adage, 'the enemy of my enemy is my friend,' holds true."
A paper on the subject by Mooney was published in the August issue of Ecology, a monthly science journal. Mooney, who received his doctorate from CU-Boulder in 2004, will become a biology department faculty member at the University of California, Irvine, in fall 2007.
In the study, Mooney used mesh netting to exclude birds from ponderosa pine limbs in the U.S. Forest Service-managed Manitou Springs Experimental Forest northwest of Colorado Springs for three years. The results showed that branches on 42 trees rigged to exclude birds had 18 percent less foliage and 34 percent less wood growth by the end of the study.
Mooney collected about 150,000 insect specimens from the mountain study area, identifying more than 300 separate spider and insect species collectively known as arthropods. The trees used in the study were set up to exclude birds, ants, or both, since ants also can have significant impacts on other arthropods, he said.
"The study indicates that pine canopies are very complex systems with an unexpected
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Contact: Kailen Mooney
mooney@tritrophic.org
607-351-5653
University of Colorado at Boulder
1-Aug-2007