Lisa Robinson photo
A Clark’s nutcracker using its bill to begin to pry open a whitebark pine cone in the tree trop.
Photo provided/Susan Ballinger
This grove of whitebark pines on the northwest-facing slope of Mission Ridge burned in September 2012. You can see that multiple tree trunks grouped together, as they all arose from a single Clark’s Nutcracker seed cache. This wildfire opened up the forest floor to sunshine, making way for a new grove of whitebark pine, once Clark’s nutcrackers replant the slope with seed caches.
The sharp scent of fresh-cut pine is a signature of the holidays and reminds us of our deep human connection to conifer trees. Our Eastside Cascade forests are home to four native pines: ponderosa, lodgepole, western white and whitebark. Pines grow signature cones, each containing seeds. Most commonly when ripe, the woody cone scales open and spread apart, exposing a seed surrounded by a papery wing that is easily carried away by the wind. However, whitebark pinecones never open on their own so their large wingless seeds remain encased inside resin-coated thick scales.
Whitebark pine (Pinus albicaulis) is one of seven world-wide stone pine species that requires a nutcracker bird to harvest and plant its seeds. Stone pines inhabit cold mountain environments and most are the highest growing conifer tree, forming timberlines. In western North America, whitebark pine’s windswept form is a signature of high county wilderness ridges and peaks. And, the guttural “Kra-a-a-k” call of the Clark’s nutcracker (Nucifraga columbiana) joins the wind as its soundscape. The range of the Clark’s nutcracker in the Pacific Northwest exactly mirrors the distribution of whitebark pine forests. Our closest whitebark pine forests are on Mission Ridge, Icicle Ridge, and in the Enchantments, so these are places to go to find resident Clark’s nutcrackers.
Year-round, the Clark’s nutcracker main food (for both adults and juveniles) are fresh and stored pine seeds. To harvest whitebark pine seeds, the bird perches in the tree next to an unopened cone and uses its long, pointed bill to pry off the thick scales. Then it plucks out a large seed that is embedded in the cone’s core. With a quick backward flip of the head, the bird uses it’s tongue to insert the seed into an elastic sack-like pouch on the floor of its mouth (think luggage carrier) that can hold up to 150 seeds or up to 20 percent of the bird’s weight. Strong wings carry the bird to a cache location, either very close by or often several miles away at a high elevation forest opening. To cache, the bird loosens the soil with its bill, brings up a single seed from the pouch, holds it in its bill, and then and pushes it about an inch down into the soil. Nutcrackers cache seeds singly, or in groups, averaging about three to four seeds/hole. The bird then conceals its cache by covering it. It continues caching seeds nearby until the pouch is empty and then the bird flies back to the tree and resumes harvesting. Clark’s nutcrackers begin harvesting whitebark pine cones in mid-July and continue through the fall, caching more seeds than are needed to sustain a bird and its young for the coming year.
Photo provided/Susan Ballinger
Our Washington native pine tree cones: Upper left, ponderosa pine; lower left, western white pine; upper right, lodgepole pine; lower right, remains of whitebark pine cones after either Clark’s nutcrackers or tree squirrels have removed the scales and harvested the seeds. Stone pines, such as whitebark, rely on a nutcracker to harvest and plant its seeds because the cones don’t open on their own.
Remarkably, Clark’s nutcrackers use memory to re-find and eat from their seed caches, winter through early summer. Not all caches are recovered, and this is the only way the next generation of whitebark pine seedlings sprout and grow. Because caches often have many seeds, multiple trees grow up in a tight group. Without Clark’s nutcracker, the forest would have no whitebark pine.
At present, whitebark pine is in decline throughout its range due to four threats, all direct results of human actions over the last century: reduced habitat due to fire exclusion and climate change, and increased tree death due to a native bark beetle and an introduced blister rust fungus.
Habitat alteration due to a century of fire exclusion means that whitebark pine face increased competition for growing space. Shade-tolerant trees like subalpine fir and Englemann spruce are not eliminated by wildfire much less frequently, so they grow and shade out the pine seeds that need a sunny forest opening to grow and thrive.
An introduced Eurasian disease, white pine blister rust, has been spreading and infecting all five-needled pines in the Pacific Northwest, since its accidental introduction in 1910. Blister rust commonly kills the upper, cone-bearing branches on whitebark pine. Recently, foresters have sought-out trees that are disease-resistant and are growing their seeds in nurseries. But the high cost of replanting a slow-growing, non-commercially harvested tree on remote mountain tops is a funding challenge.
The next two threats are a direct result of climate change. Over the past few decades, warmer than historically average summers and winters at high elevations has accelerated the life cycle timeline for the mountain pine beetle, a native tree-killer. As beetle densities increase, a greater number of whitebark pines are attacked, and subsequently, die. The warming trend at high elevations reduces the habitat available to whitebark pine, as they can’t move to any higher, cooler ground. The synergy between all of these combined threats mean that whitebark pine as a species is in severe decline, and our window to take action is narrow.
Susan Ballinger teaches a 12-week Wenatchee Naturalist course every fall at Wenatchee Valley College. This winter, Ballinger will offer a conifer identification workshop and two birding short courses through WVC Continuing Education.