In the study, aimed at determining how effective the birds are in regenerating whitebark pine, the researchers fitted 54 Clark's nutcrackers in the Olympic and Cascade Mountains with radio collars and tracked them for three seasons. They found that:
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 in sheltered locations at the driest, lowest elevation sites within their rangeareas unsuitable for successful whitebark pine germination
"One of the most important things this study helped us to understand is how unlikely it is that whitebark pine seeds will end up in good germination spots," Raphael said. "Birds placed only about 15 percent of the seeds they gathered in places where germination is actually possible."
In addition to revealing that Clark's nutcracker caching alone, while critical, would not be sufficient to recover populations of whitebark pine, the study also is the first to document the role of the birds in disseminating the seeds of ponderosa pine. 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.
"Because we 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 ponderos
|Contact: Yasmeen Sands|
USDA Forest Service, Pacific Northwest Research Station