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Monday, 19 October 2015 19:28

Blue Jays & Acorns

BlueJaywithAcorn

"A blue jay with an acorn in its mouth, flying to locate a spot to store it for future consumption. Notice the distended throat, an indication the bird has stored a few more acorns in its gular sac, a special pouch in its throat used to store food".

Come the cooler weather many wildlife species begin to harvest and store as a strategy to prepare them for the oncoming winter, when food supplies are much reduced. Observing the interesting behaviors of animals as they undertake this critically important task can be a fun part of your autumn outdoor experience. The food gathering behavior of one specific animal - blue jays (Cyanocitta cristata) - was recently on my mind as I sat in a third floor office during a business meeting.

At the meeting I had a clear view out the large double window situated behind one of the participant’s desk which provided an expansive view of the sky and hillside outside of the building situated upon a hilltop. About once a minute a blue jay would fly past the window moving from right to left carrying something large in its mouth. Just as frequently another bird, empty-mouthed would fly in the opposite direction. It took a couple of window passes before I realized what was going on - the blue jays were collecting oak acorns and carrying them away to cache them for future use. 

Caching food is a common strategy a number of mammal and bird species employ to tide them through the winter. Squirrels and chipmunks are well known for harvesting large amounts of nuts and seeds and storing them underground to be drawn upon as needed on cold winter days. It is the same in the case with blue jays. A bird will pick a spot to its liking and place an acorn in the ground, typically in soft, moist soil which is more pliable to a jay’s bill. With their survival depending upon an adequate food supply they become industrious animals during the fall, especially the month of October. This industriousness was revealed in a 1986 study in which researchers documented 50 blue jays caching 150,000 acorns in a month - an average of about 110 acorns per bird per day. Moving this number of acorns is assisted by the fact that blue jays can transport several acorns at a time by storing a few in their gular sac, a storage pouch in their throat, and carrying a few more in their bill.

An unintended but unsurprising result of all this acorn caching are the growth of individual oak trees and the spread of oak forests. Blue jays have impressive memories as do all members of the Crow or Corvid family to which they belong. (In fact, their distant cousin, the Clark’s Nutcracker remembers the locations where it has cached thousands of pine nuts). But still, the bird cannot remember every nut or acorn. Or maybe a blue jay plants an acorn and on its way back to get more it becomes food for a Cooper’s Hawk. In any case some untouched acorns, stored a mile or more from the parent tree and having been planted in a good soil environment, sprout and grow.

Thus, we may have blue jays to thank for much of the oak forests of Long Island, the New England area, and the entire eastern United States. In fact, before acorn caching by jays was observed and described in the literature it was a mystery as to how, after the last glacier retreated, the oak forests in the northeastern United States and southern Canada became re-established so quickly. After all, unlike wind blown seeds that can be carried on the wind for great distances, acorns aren’t going to disperse very far from the tree they developed on.  But blue jays with their acorn-caching habits greatly accelerated a return of our forests. When I learned this I never looked at Blue Jays the same way again.

- John Turner, Conservation Policy Advocate

Blue Jay photo - Luke Ormand (c) 2015 

Last modified on Tuesday, 20 October 2015 20:32
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