Of blue jays and pin oaks: How jays have shaped our oak forests around the world

blue jay bird holding an acorn in its beak
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Winter is a time for reflection. We often spend more time inside looking outside during the Illinois winter. Perhaps one of the most popular past times for many of us is watching the birds, which often stand in stark contrast to the still winter landscape. It is through this, that I learned something fascinating about the relationship between blue jays and oak trees.

Introducing the Oak

My journey of observation began this past autumn. In our backyard stands a massive pin oak (Quercus palustris). Pin oaks can grow into 100-foot-tall behemoths. This particular tree provides excellent shade for the house, however, if I were to direct the hands planting it 30 years ago, I may have suggested a bit farther away from the house. I’m not sure who is more guilty of clogging my gutters more, the oaks or the maples. Both seem to be working together to keep me on the ladder at all times of the year. This past fall our pin oak did something I have not yet observed of this particular tree. It had a mast year.

A mast is where a tree puts an enormous amount of energy into seed production. In the case of the oak, the seed is the acorn. Many different species of trees show this tendency of years with low fruit production to an overabundance. The theory behind this is the idea of providing so much food for those animals eating the seed, there is no way all the acorns could be eaten, thus ensuring some offspring of the tree will survive predation.

What does a mast year mean for the pin oak in my backyard? Essentially, a carpet of acorns on the ground. The area beneath the tree is so full of acorns, the lawn is mostly smothered. And the gutters are full, almost comically so, of acorns. Looking into the canopy of the tree as winter set in, I noticed clusters and clusters of acorns still holding fast, not having dropped yet. You get the picture; it was a lot of acorns.

Enter the Jay

With all these acorns it seems to make sense how widespread oak trees are around the planet. Of course, the tree can’t move its acorns far and wide. Something must be responsible for sowing oaks across the landscape. Some may credit squirrels for this enormous task, and they likely do their fair share of work, but the animal credited with oak dispersal planet-wide are the jays. There are many different species of jays around the world. For us here in Illinois specifically what we see is the Eastern blue jay (Cyanocitta cristata).

And this lined up precisely with what I was seeing in my backyard. Blue jays were swarming the pin oak. Early in the fall they would grab acorns out of the canopy or from the ground and fly off out of sight. During the winter I observed blue jays pluck acorns from the ground and fly into the tree and peck away at the hard shell to get to the nut inside. Smaller birds waited below on the ground gobbling up any stray pieces of acorn meat falling from the sky. Both the cats and I were enchanted with the spectacle going on in the backyard.

The Link Between Jays and Oaks

While it may be new knowledge to me, this relationship between blue jays and oaks is already well-known. About mid-winter I sat in an online conference where the keynote speaker was Dr. Doug Tallamy, an entomologist with University of Delaware. He was describing the multitude of benefits native trees, specifically oaks, provide to wildlife. He then brought up blue jays and acorns and I sat up on the edge of my seat. Turns out various species of jays and oaks are tied together all over the planet.

In the fall, the blue jays in my yard were stockpiling acorns. They will fill their beaks and then fly to an isolated location to bury the acorn. If there so happens to be another blue jay nearby, the bird will continue to fly until there are no others to see where it caches its prize. Ornithologists believe blue jays even know when being observed by other species like humans and will scramble their behavior, making research on them difficult. According to UC Berkley’s Thomas Scott, an industrious group of jays can move “a forest worth of trees every autumn.” Scott cited an article titled Airlifting the Oaks (Natural History 10/86:41-46), that discovered “50 jays transported and cached 150,000 acorns in 28 days, about 110 acorns per day for each bird.”

Like the tree rat (aka squirrels), the blue jay will not recall every single stash of acorns. And in the case of my pin oak, will not need to as the abundance of acorns is still present even as we enter spring. Airlifting the Oaks authors Carter Johnson and Curtis Adkisson, also discovered acorns stashed by blue jays had a higher germination rate than those carried away by other species and they planted at an ideal depth for germination. Making it possible that blue jays are selective in what acorns they choose to cache. Credit may also be placed on the jays with spreading oaks far and wide following the last ice age.

This knowledge has brought about a newfound appreciation for the eastern blue jay. Hopefully, your winter brought new discoveries of the natural world. Now I don’t know about you, but I think I’m ready to stop watching from the inside and get out there to do some work. Even as we toil in the yard this season, don’t forget to stop and observe the pageantry of the natural world around us.

Good Growing Tip of the Week: In addition to acorns, blue jays will frequent tray or hopper feeders preferring sunflower seeds, peanuts, and suet.

Source: Jays Plant Acorns, by Thomas Scott, UC Berkley

 

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MEET THE AUTHOR

Chris Enroth is a horticulture educator with University of Illinois Extension, serving Henderson, McDonough, Knox, and Warren counties since 2012. Chris provides horticulture programming with an emphasis on the home gardener, landscape maintenance personnel, and commercial landscapers. Additional responsibilities include coordinating local county Master Gardener and Master Naturalist volunteers - providing their training, continuing education, advanced training, seasonal events, and organizing community outreach programs for horticulture and conservation assistance/education. In his spare time, Chris enjoys the outdoors, lounging in the garden among the flowers (weeds to most).