Out My Backdoor: Backyard Wildlife Love Acorns

By Terry W. Johnson

Acorns rank as one of the very best wildlife foods. For generations stately oaks have been rooted in backyards across the state. Although the beauty of these trees has long been recognized, their importance as valuable food plants for backyard wildlife remains largely unappreciated.

With more than 30 species of oaks native to the Peach State, regardless of whether you live in the city or country, the mountains or the coast, there is an oak that will grow in your backyard.

The fact of the matter is that a myriad of our backyard wildlife neighbors are attracted to acorns like iron filings are drawn to a magnet. In fact, approximately 150 species of wildlife eat acorns. The lengthy list of the mammals and birds that frequent our backyards in search of these brown, food-rich nuggets includes blue jays, woodpeckers, fox and gray squirrels, eastern chipmunks, brown thrashers, tufted titmice, common grackles, rabbits, white-tailed deer, gray and red foxes, eastern towhees, rusty blackbirds, Carolina wrens, brown thrasher, dark-eyed juncos, and white-breasted nuthatches.

The meat within the acorn's tough hull is jam-packed with carbohydrates, fats and vitamins. As such, acorns help many wildlife species maintain skeletal and muscle health during the winter months when food is often scarce.

Eastern towhee eating an acorn. (Terry W. Johnson)

A few decades ago the results of a study by a wildlife biologist demonstrated just how important acorns are to wildlife. The researcher found that 83 percent of a year's crop of acorns is eaten by wildlife, 6 percent is consumed by weevils and other insects and some 10 percent is naturally defective. This leaves less than 1 percent of the acorns to sprout and produce a new generation of oak trees.

As you might expect, not all acorns are created equal; wildlife prefer some over others. These preferences seemed to be linked to the size of the acorn and its taste. The result is that some acorns vanish within weeks of hitting the ground, while others still litter the ground the following spring.

White-tailed deer, for example, favor white oak acorns far more than the others. This is because white oak acorns contain just a smidgeon of tannic acid, giving them a sweeter taste. For this reason, white oak acorns are the usually the first to disappear. Acorns that are high in tannic acid are very bitter. As a rule, oaks in the white oak group produce acorns that contain less tannic acid than trees in the red oak group.

It is easy to tell which oaks belong to which group. Members of the white oak group have leaves with rounded lobes and leaf margins free of bristles. Crack open the shells of these trees’ acorns and you will see that they are hairless inside. Their acorns mature in one year.

In comparison, members of the red oak group sport leaves with bristle-tipped lobes or smooth margins. The interior of the shells of their acorns are hairy. These acorns take two years to mature.

The size of an acorn also affects whether or not an animal eats the acorns of certain oaks. Some acorns are simply too large for certain animals to swallow. However, this obstacle can sometimes be overcome.

I have often seen many small birds congregate in city streets where acorns have been crushed by the tires of passing cars. The birds brave traffic to eat tiny pieces of acorns left after being run over.

I once witnessed a mixed flock of grackles and blackbirds descend on a small grove of oaks standing in a front yard. During the flocks' feeding frenzy the birds neatly clipped the caps from the acorns hanging on the trees. As the birds ate, they dropped many of the acorns they had selected. These mishandled acorns rained onto the ground. It wasn't long before a small flock of dark-eyed juncos arrived and began feeding on the exposed meat of the fallen acorns.

Some of us are blessed with one or more oaks growing in our yards. However, if you do not have an oak spreading its branches over a section of your yard, and want to plant one that will offer your wildlife neighbors food, you must realize that it will take some time before your sapling will produce its first acorn.

Some oaks, such as the water oak, can begin bearing acorns at age 20, while other oaks do not begin developing acorns until they are 40-50 years old.

Once an oak begins yielding acorns it will do so for years. White oaks, for example, will bear acorns for centuries. However, the number of acorns produced by a tree can vary tremendously from year to year.

White oaks produce a bumper crop every four to 10 years, while most other oaks bear a bumper crop every three to four years. In the “off” years, many oaks yield just a fraction of the number of acorns they do during a bumper crop. While no one knows for sure what triggers a bumper crop, some experts suggest that weather may play a key role in acorn production.

There are several things that you need to keep in mind if you decide to plant an oak in your yard. First, consider the size of your yard. Some oaks grow taller and spread wider than others. Select a variety that won't totally dominate your landscape. This is important, as regardless of which oak you select, as it grows it will begin shading out portions of your yard that may be dedicated to flower beds, lawns or sun-loving shrubs.

Also, it is a good idea not to plant an oak within 50 feet of your home or a sidewalk. Underground roots can crack concrete sidewalks and foundations. In addition, the last thing that you want is for you oak to fall on your home during severe weather.

Planting an oak is obviously not an option for all homeowners. However, should you decide that an oak is perfect for your home landscape, select an oak that produces an abundance of acorns and is native to your neck of the woods. The Georgia Forestry Commission, www.gfc.state.ga.us, can provide recommendations on which oaks do best in your region of the state.

Terry W. Johnson is a former Nongame program manager with the Wildlife Resources Division, a backyard wildlife expert, and executive director of TERN, the friends group of the Nongame Conservation Section. (Permission is required to reprint this column. Contact rick.lavender@dnr.ga.gov.) Learn more about TERN, The Environmental Resources Network, at http://tern.homestead.com. “Out My Backdoor” archive.