The study also has implications for large areas of the West ravaged by forest fires in recent years, he said. A number of once formidable stands of mature ponderosa have been burned and logged and subsequently replaced by smaller pines that offer limited breeding opportunities for cavity-nesting birds like chickadees and nuthatches, which nest and lay their eggs in the holes of large trees and dead snags.
"This is a very rigorous study that essentially shows that even modest little birds like chickadees and nuthatches can help improve the heath of the trees, which are the monarchs of the forest," said CU-Boulder biology Professor Yan Linhart. Linhart was Mooney's doctoral adviser at CU-Boulder and also co-authored a study with Mooney in 2006 in the journal Animal Ecology. The study compared the effects of birds on pine with their effects on dwarf mistletoe, a parasitic plant on ponderosas throughout the West.
Mooney said the activity of the birds also was shown to change the chemical "flavor" of the trees, which may have implications for infestations by damaging insects like bark beetles that have ravaged pine forests in the West. Chemicals in trees known as terpenes, which give vegetation distinctive odors, have been implicated in the resistance of trees to parasites and plant-eating insects, he said.
By removing insects, the birds indirectly altered the terpene composition of pine tissues, said Linhart. The alteration of terpene "flavor" can have wide ranging effects, since terpenes influence decisions that creatures like bark beetles, porcupines and squirrels make when deciding which trees to eat, said Linhart.