Nature: Blue jays eat and spread acorns, helping many oak trees grow – The Columbus Dispatch

This is the 408th column I’ve written for The Columbus Dispatch, and I’ve rarely written about the same subject twice. “Nature” covers a lot of turf and it’d be easy to write a weekly column for eternity and never repeat topics.
The blue jay is an exception. This is my third column on these brash crow family members, and it may not be the last.
This time, I want to give jays credit as avian Johnny Appleseeds for the oak family. Many species of birds play vital roles in the dispersal of plant fruit. Indeed, the botanical world abounds with fruit that co-evolved to lure birds. Perhaps the most easily observed examples are bright berries. The colorful pulp is irresistible to the frugivorous (fruit-eating) crowd, and birds often wolf down such fruit with abandon. The hard seeds within often survive the ride through the digestive tract, to be expelled far from the source shrub or tree. Birds make great agents for broadcasting fruit far and wide.
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In the case of oak trees, the fruit are acorns. Hard-shelled fruit produced by woody plants such as beech, hickory, and oak is termed mast. Many animals covet mast: deer, mice and other small mammals, squirrels, red-headed woodpeckers, wild turkey, and many others.
But perhaps no animal can compare with the importance of blue jays to oaks and their dispersal.
Come fall and the ripening of oak fruit, the blue jays set to work harvesting the acorns on a truly epic scale. We’re in the midst of the jay’s harvest now. If you observe blue jays consistently flying to and fro on the same flight pattern, and oaks are around, you can be sure they’re raiding acorn-rich oaks.
On Oct. 23, I was at a site in Licking County rich in pin oaks. Squadrons of jays regularly passed overhead and it didn’t take long to see what they were up to. On each return trip, the birds were toting acorns and usually more than one. I made the accompanying image that day, and the jay is carrying five acorns! Two are in its bill, the tip of another protrudes from its mouth, and its throat bulges with (at least) two others.
I watched the birds for perhaps three hours, and the dozen or so acorn-hauling jays probably harvested well over 100 acorns during that time. Blue jays are so engaged all over Ohio, and eastern North America.
Where are they going with their oaken plunder? Like feathered pirates with stolen booty, the jays bury their treasures. An acorn-laden jay finds suitable soil, tries to ensure no one is watching, and quickly tamps the acorns into the ground. The bird will often cover the burial site with small stones or leaves to hide the evidence.
Unfortunately for the jays, they will forget where they hid many of those acorns. That’s good for the oaks, though. As one hard-working jay might plant a few thousand acorns annually, a better disperser of the trees’ spawn could not be designed. Jays will retrieve acorn caches when times are tight, and other animals will discover some. But many will go undetected and sprout new oaks.
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The epic scale at which blue jays plant acorns and other mast may be the primary reason that mast-bearing trees rapidly expanded northward on the heels of the last glacial period. Reid’s Paradox is a term for the apparent discrepancy between expected northward plant expansion based on typical seed dispersal rates, and the much greater rapidity that this occurred as shown by fossil evidence.
Paleobotanist Clement Reid, namesake of the paradox, came to the conclusion that highly mobile bird vectors were the most likely factor in expediting post-glacial floristic advances. In eastern North America, the blue jay may be the linchpin of Reid’s Paradox.
Naturalist Jim McCormac writes a column for The Dispatch on the first, third and fifth Sundays of the month. He also writes about nature