Clark's nutcracker caches up to 20K seeds per year - and remembers where
Calling someone a ‘birdbrain’ should be a compliment, says naturalist
While it's often used as an insult, calling someone a birdbrain should actually be a compliment, says CBC Alberta's resident wildlife expert Brian Keating.
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For instance, the Clark's nutcracker, a bird that is part of the Corvidae family found across western North America, creates between 5,000 and 20,000 separate seed caches throughout its home territory each year — committing each individual treasure trove to a map in its brain.
Starting in the summer, the nutcrackers dart from tree to tree, using their beaks to pry into cones and collect seeds. The Whitebark pine tree is a particular favourite.
According to a study by H.E. Hutchins and R.M. Lanner published in the journal Oecologia in 1982, the birds can collect 32 seeds per minute, depositing them into pouches located under their tongues. Each Clark's nutcracker can carry about 100 seeds at a time, Keating said.
From there, the birds go in search of hiding spots, pecking holes in the topsoil, burying seeds under leaf litter and and in nooks high up on trees.
And their job is not done until the cold weather arrives, usually in November, Keating says.
Then, the birds switch from hiding to seeking.
While no one knows exactly how the birds find their many seed caches, there are two major theories:
- The nutcrackers may memorize two or three permanent landmarks or object in the vicinity of their caches; they later triangulate the cache's location based on proximity to the landmarks.
- Other biologists believe the birds note landmarks, but rather than relying on distances, they use angles to find their cache.
Of course, snow complicates the process — particularly if some of the landmarks are buried. That's why you will sometimes see a nutcracker perch on a low-lying branch to survey the area before swooping down and digging. Occasionally, the birds will return to their branch and survey once more before trying another spot, slightly over from the original.
In the 1970s, biologist Stephen Vander Wall tried to test the triangulation of several captive nutcrackers by moving some of the markers in their cage, publishing his findings in Birds of the Western Slopes. Predictably, moving the markers interfered with the nutcrackers' ability to find their food.
In the wild, Clark's nutcrackers rely on the caches into the spring months when their chicks are fledged — and then it's time for a new season of saving.
Of course, there are stored seeds every year that are never reclaimed. Because nutcrackers tend to favour hiding spots favourable for seed germination, a clump of left-behind seeds can quickly form a noticeable pocket of new growth, making it clear that a smart bird has been there.