Bird May be Key to Survival of Declining Northwest Tree
|Clark's Nutcracker by Teresa Lorenz
(April 12, 2011) There is growing concern about the long-term survival of the whitebark pine, which is a keystone species in the high-mountain ecosystems of the northern Rockies, Cascades, Olympics, and eastern Sierra Nevada. According to a new report by the Forest Service's Pacific Northwest Research Station published in Science Findings, the Clark’s Nutcracker may hold the key to the tree’s future.
It is well known that the whitebark pine tree is experiencing declines of 45 percent in some areas as a result of outbreaks of the mountain pine beetle and blister rust. What was not known until now was the complex relationship between the whitebark pine, the Clark’s Nutcracker, and another tree that seems to be quite important to the bird.
The whitebark pine tree appears to need the Clark’s Nutcracker because, unlike most other pines, its cones do not open on their own to release their seeds, but must be forced open by the nutcrackers. According to the study, the nutcrackers flock around whitebark pine stands in autumn as the cones ripen, and use their sharp, strong bills to hammer into the tightly closed cones and dig out the seeds, cone chips flying in the process.
The bird caches seeds in the ground throughout late summer and early fall. The birds’ remarkable memory allows them to retrieve seeds from their caches throughout the winter, but those that remain are left to germinate.
“This study demonstrates once again how our environment is a fabric made of many interdependent and interwoven threads. Pulling on one thread can cause the unintended unraveling of the whole cloth,” said Mike Parr, Vice President of American Bird Conservancy, the nation’s leading bird conservation organization.
“This illustrates one reason why we are concerned about the potential loss of any single species – we don’t often know all the ripple effects from a species going extinct,” said Parr.
The study, which involved fitting 54 birds with radio collars for three seasons, also documented the important role of ponderosa pine seeds as a food source for Clark’s Nutcracker as well as, for the first time, the effectiveness of the bird in disseminating those seeds for germination. The nutcrackers not only routinely gathered ponderosa pine seeds within their home ranges, but were more effective in dispersing them to suitable germination sites than they were at dispersing whitebark pine seeds.
Included in the study’s key findings:
- The nutcrackers foraged widely for whitebark pine seeds, but transported nearly all of them back to their home ranges for caching, which suggests that natural generation of the tree would be greatest within the birds’ home ranges.
- The nutcrackers transported seeds over much longer distances than previously observed, sometimes up to 20 miles, which suggests that the birds facilitate a great amount of genetic mixing of the tree.
- The nutcrackers tended to cache their seeds, about 85 percent of the time, in sheltered locations at the driest, lowest elevation sites within their range—areas unsuitable for successful whitebark pine germination, which makes their role all the more important.
Because the study found ponderosa pine seeds to be an important food for nutcrackers in Washington and Oregon, the success of whitebark pine restoration may be irrevocably linked to the conservation of low-elevation ponderosa pine.
American Bird Conservancy (ABC) is a 501(c)(3) not-for-profit membership organization whose mission is to conserve native birds and their habitats throughout the Americas. ABC acts by safeguarding the rarest species, conserving and restoring habitats, and reducing threats, while building capacity in the bird conservation movement.