Seeing the Mountain through the Trees: More on Nutcrackers and Pines

Photo: Gunnsteinn Jonsson, via Wikimedia Commons

Not long ago, I wrote about how whitebark and limber pines and Clark’s nutcrackers are co-dependent: nutcrackers chisel away at whitebark cones, carry off these living seeds under their tongues, and store them for the winter; but they accidentally forget some as the season passes, and so plant new trees. Well, recent research in the Cascades adds yet another chapter to this story.

During a U.S. Forest Service study, researchers radio-tracked 54 nutcrackers, and here’s what they found: Nutcrackers do forage widely for whitebark nuts. But rather than caching them nearby, they carry them back to their home range, sometimes as far as 20 miles away. Such a distance is great for the genetic diversity of whitebark pine populations, because it mixes the trees. However, the birds tend to hide their seeds in the lowest, driest elevations of their territories—which makes sense, right? Wouldn’t you also store your food where you could reach it most easily, first placing your stores (or store-bought goods) on the lowest, most-accessible slopes (or shelves)? But as a result, the Cascades' nutcrackers hide only 15 percent of the whitebark nuts they collect in niches where germination is even possible. So while the birds' unwitting propagation and distribution of the species is essential, it may not be able to keep pace with how quickly whitebark pines are dying as alpine zones continue to warm.

And then, there’s this: the study showed that nutcrackers reliably gather ponderosa pine nuts as well. This larger pine, with its puzzle-like bark, grows lower down on the mountainside, and thus the birds more consistently hide ponderosa seeds in just the zone where they might grow. Nutcrackers are pretty important to ponderosa forests, it seems, and vice versa. So to save whitebark pines—which are closely tied to nutcrackers, but by a more fragile strand than we once thought—the conservation of ponderosa forest also becomes essential. And that, to my mind, lassos just about the whole mountain—it’s all one story, unfolding.