A friend once asked me for advice on how to paint a seasonal mural. He wanted to know which plants and animals best represented each season in our region. There are so many options! Evergreens and red cardinals in winter, flowers and frogs in spring, butterflies and bees in summer are just a few that come to mind.
I contemplate this question again, as we cycle into fall. Autumn brings cloudy mornings, dewy spider webs, cool air mixed with a warm breeze, warm reds, yellows and oranges appearing on tree-covered slopes. It is a time for the harvest, the seeds, the chubby marmots and the earliest nights. Two things I would definitely recommend putting on the mural for fall are blue jays and oak trees.
Blue Jays are a conspicuous and common bird. Their loud, raucous calls are heard in most habitats, including backyard bird feeders. They are large in size with striking colors and patterns and one of the easiest birds to identify. I have gotten used to showing a picture of this distinctive bird and making 4 year olds scream “Blue Jay!” with certainty and joy.
Many of their behaviors, including their ability to dominate a bird feeder, make them unpopular with some bird lovers. However, blue jays provide a critical service to our forests through their foraging and storage behavior. Therefore, although they are present in our region in all seasons, I associate them more with autumn than with any other season. More on the Blue Jays in a bit.
The other essential element in a fall mural is an oak tree. There are hundreds of species throughout the world. Oak trees provide food, shelter, shade, and water absorption wherever they are found. Thousands of leaves fall, returning nutrients to the soil with the help of bacteria, fungi, and other creatures that slowly break down the leaves. Many oak-loving insects fall from the tree and pupate in the leaf litter below.
In the fall, oak tree seeds known as acorns also ripen. In its lifetime, a tree can produce up to three million acorns: compact packages of carbohydrates, fats, and proteins that can be eaten but also stored. As food, acorns support dozens of species of wildlife, including turkeys, deer, squirrels, wood ducks, and bears. And Tiles!
A squirrel running out from under an oak tree with an acorn in its mouth is a common sight in the fall. Finding the partial acorn shell on a log, with the insides chewed up, is also not unusual. But from the plant’s perspective, why produce a seed that is simply eaten and digested? An acorn does not have a hard seed that passes through an animal’s digestive system, coming out in its poop. It has no hooks to attack animal fur and no wings to travel with the wind.
Oak trees have a different strategy for spreading their seeds. They count on their seeds to be stored and forgotten. Squirrels are often associated with oak trees. That’s right. Many species of squirrels store acorns to eat during the winter. Some of those acorns are never found. The squirrel can be forgotten or eaten. Then the seed has a chance to sprout and become a new tree. However, the prize for scattering acorns does not go to the squirrel, but to the blue jay.
Blue jays also eat and store acorns for the winter, but in a way that also benefits potential future tree sprouts. While a squirrel can bury acorns up to 200 feet from the tree, a blue jay can move the acorn up to a mile away. Blue Jays can also carry up to five acorns at a time. They carry one in their mouths, one on the tip of their bill, and two or three in a specialized pouch in their throats called the gular pouch. They also store one acorn at a time, often on the ground. Is there a better way to plant a tree?
(It is also important to note that “frequently” is not the same as “forever”. I once saw a blue jay hide acorns in the thick moss that grew on my garage roof. Is there a worse way to plant a tree?)
Blue jays and oak trees have a well-studied relationship. In one study, six birds with radio transmitters were found to hide between 3,000 and 5,000 acorns each in one fall. Jays not only have a fondness for acorns, they are also good at detecting which acorns have been infested with weevils and which have not. Acorn weevils lay their eggs on the developing acorn, and the larva eats all of the acorn’s flesh. In autumn, the weevil emerges through a small hole in the acorn, but the acorn no longer grows. Blue Jays are very good at not storing weevil-infested acorns.
Blue Jays inadvertently plant trees that will grow and produce seeds long after they are gone. With the number of acorns blue jays lay down, they can start a forest in their lifetime. In fact, blue jays are thought to be the reason oaks spread north so quickly after the last glacial period.
Found throughout the eastern and central United States, blue jays aren’t the only birds to move acorns. Other jay species around the world also scatter acorns and other seeds.
In these kinds of relationships, we might wonder who benefits. Is the blue jay helping the oak or is the oak helping the blue jay? The answer is both, and more. I think we benefit from these mutualistic relationships. We sit under or climb the branches of an oak tree. We use wood to create things we need and want. We can even eat the acorns, if you’re adventurous that way. And we learn and witness the amazing way the world works.
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