Forest Foragers of Whitebark Pine Seeds

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Recently, I enjoyed two nights of permitted backpacking and camping just above Lake Caroline. Our group had a surprisingly close encounter along the trail with a black bear. It ignored us, as it was focused on the whitebark pinecone in its mouth, working to extract plump seeds. At camp, a few feet from our tent, a pair of golden-mantled ground squirrels busied themselves by scampering to the top of a whitebark pine, fiddling around with a partly-eaten cone, and then returning to a log to remove the outer seed coat and then eat the plump seed.

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As I looked up, crowns of whitebark pine trees glistened with abundant ripe cones. Overhead, we hear the distinctive calls of a group of Clark’s nutcrackers flying downslope. Four individuals were calling to one another, as they flew in tandem, white edged tails flashing.

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These are the characters in the amazing story of whitebark pines and how they disperse seeds.

September is peak conifer cone ripeness throughout the western U.S for dozens of species of pines, firs, and spruces. Locally, in the upper reaches of the Icicle River watershed, whitebark pinecones project from the tops of trees. The cones are deep red and covered in resin so they glisten in the sun. The seeds are large and desirable food sources for a variety of native wildlife.

Regionally, populations of pines (and many other tree species) produce large cone crops in a boom-or-bust pattern that is termed masting. Masting means that cone crops are highly variable and synchronized. This reproduction strategy ensures that seed predator mammals and birds can’t possibly eat all seeds, so some seeds survive and grow into next generation of trees. This year, at 6000-7000 feet in the Icicle drainage near Lake Caroline, the whitebark pine cone crop is abundant. The seeds are large, nutritious (>50% fat), and long-lasting making them highly desirable as a food source for wildlife.

Our region’s other native pine – ponderosa, lodgepole, and western white pine – have scales that open and allow the seeds to be blown out by the wind. Whitebark pine cones never open on their own, requiring the assist of a bird to make seed dispersal possible.

Whitebark pine rely upon the Clark’s nutcracker to disperse and plant the next generation of seed-grown trees. The birds perch in the tree top, pry open the cone, extract the seeds, store them in an under-tongue pouch, and then transport the seeds to either an above ground or underground cache. The birds return to harvest their own seed caches, but some are forgotten, and these can potentially sprout and grow. However, recent research has shown that nutcrackers cache a small percentage of seeds in habitats that are well-suited for seed germination. Whitebark pine seeds sprout and grow successfully in partial shade in mostly bare soil at high elevations. Nutcrackers cache in a wide variety of places and elevations, both above and below ground. Researcher Teresa Lorenz documented an individual bird caching over twenty miles away from the tree, farther than any other North American rodent, bird, or even the wind, disperses seeds! Most of these cache sites are unsuited for seed sprouting. The fact that whitebark pine forests exist tells us that the birds cache a huge actual number of seeds, since a low percentage are placed in habitats that have the potential for a seed to sprout. Read more about the history of Clark’s nutcracker field research here, learn about recent research conducted in the eastside Washington Cascades by Teresa Lorenz here, and watch a short video featuring researcher Taza Schaming here, all on the Cornell lab of Ornithology website.)

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Can you see evidence of seed removal in the photo above? Most of these cones have been opened and emptied of their seeds by this native nutcracker. Likely, over the coming days, Clark’s nutcrackers will return and continue harvesting seeds, then fly away to cache them, safely stored to become a future meal.

Red squirrels (ours is the Douglas squirrel) compete with Clark’s nutcrackers for whitebark pine cone seeds.

Red squirrels use their sharp incisors to cut down the ripe cone, and let it fall to the forest floor. The squirrel uses its paws to manipulate the cone while biting away the scale and extracting the seed from it’s hard outer seed coat. If not consumed on the spot, the entire cones are stored in underground cavities for later consumption. The seeds store well and are consumed for up to one year.

Curious to learn more about whitebark pine? Start with my older blog, Take Action to Protect Whitebark Pine, and read Cornell Lab of Ornithology’s Soul mates:  Nutcrackers, Whitebark Pine, and a Bond that Holds an Ecosystem Together,  an article by Gustav Axelson in the Autumn 2015 issue of Living Bird Magazine.

Will whitebark pine forests be present in our region in the future? My hearts is hopeful, but my head is concerned. The Whitebark Pine Foundation website has resources about wildlife and current threats to this iconic species. I conclude with an excerpt from the Whitebark Pine Foundation webpage:

Why Does Whitebark pine Matter? These majestic pines are in peril; trees with reddening dead foliage or lifeless grey skeletons replace the greenery, squirrel and nutcracker activity.

Three threats act in synergy to cause this destruction:

• an introduced fungal disease called white pine blister rust,
• outbreaks of mountain pine beetles, and
• increased competition from shade-loving trees caused by fire suppression (see Threats page).

A fourth threat looms over all: climate change, which will ultimately affect the distribution of all species, and is the likely driver behind current mountain pine beetle upsurges. The decline of whitebark pine is compounded by the loss of other forest components: wildlife, other flora, and water resources, which directly impacts humans.