Got Nature? Blog

Every hunter knows the importance of acorns for game and non-game species alike. When acorns are plentiful it can alter the movements and patterns of game species and when acorns are absent wildlife must rely on alternative food sources to meet their nutritional needs during the fall, winter, and early spring. Knowing the importance of acorns to many wildlife species, it is beneficial to identify which trees are the most reliable and best producing in the woods.

Intro to oaks

White oak acorns are clustered at the end of the branch – this year’s growth, like on this swamp white oak on the left. Whereas, red oak acorns are farther down the branch at the end of last year’s growth, like the northern red oak acorns on the right. (Photo by Brian MacGowan)

Oak trees in Indiana fall into 1 of 2 groups, white oak (e.g., white, swamp white, and chinkapin) or red oak (e.g., northern red, black, and pin). White oaks produce acorns in 1 growing season (acorns falling in 2016 are from flowers that were pollinated in the spring of 2016) and red oaks produce acorns in 2 growing seasons (acorns falling in 2016 are from flowers that were pollinated in the spring of 2015). This means a late frost in the spring may result in poor acorn production in white oaks in the fall of the same year, but will not influence red oak acorn production the same fall. However, a late frost in back-to-back years may result in a mast failure from both groups.

White oak acorns tend to be selected by wildlife more than red oak acorns because they contain less tannins resulting in a less bitter and more digestible acorn. Check out the Native Trees of the Midwest to learn more about oaks, their value for wildlife, and help you learn to identify different species.

Oak trees can be split into production groups based on their relative acorn production capabilities. Some individual oak trees are inherently poor producers and rarely produce acorns even in a bumper crop. Whereas other individuals are excellent producers and may produce acorns even in the poorest year. Research from the University of Tennessee reported poor mast producing trees represented 50% of white oaks in a stand and produced only 15% of the white oak acorn crop in a given year, whereas excellent producing trees represented 13% of white oaks, but produced 40% of the total white oak acorn production. When you included excellent and good producing white oaks together (31% of trees), they accounted for 67% of the total white oak acorn crop in a stand. This means a minority of the white oaks in a stand may produce a majority of the acorns!

Scouting oak trees
Understanding that some individual oak trees are poor producers, some are excellent, and some fall between poor and excellent, surveying oak trees can help identify important mast producing individuals. The late summer and early fall, just prior to or at the beginning of acorn drop, are perfect times to identify the best and worst producing oaks in your stand of timber. Scouting can be as formal as conducting a mast survey, National Deer Association, or as informal as taking mental notes of oak trees with heavy crops of acorns on the ground while you are walking to and from your tree stands in the fall. Either way, scouting oaks for acorn production capability can provide more information when determining where to hunt in the fall or which trees to retain and which trees to remove during a timber harvest. If wildlife management is an objective on your property, trees that you identify as the best acorn producers in the woods can be retained during a timber harvest, while poor producing trees can be removed with little detriment to overall acorn production. It is important to remember to retain a balance of oaks from both the red and white oak group, favoring red oak, to help safeguard against complete mast failures.

Forest management is insurance for mast failure

The top photo is of a mature forest with very few canopy gaps resulting in very little cover or food for wildlife. The bottom picture is of a forest stand where undesirable trees have been girdled (tree on the right-hand side of picture) to increase light to the forest floor and where multiple prescribed fire have been conducted to increase forage production and cover.

Annual acorn production in a stand of oaks is highly variably and can be dependent on environmental conditions. For example, late frosts, poor pollination, and insect infestations all can be culprits for poor mast production across a stand of oaks. Because of these factors, white oaks tend to only produce reliably 2 out of every 5 years, meaning 3 out of 5 years (60%) there is poor mast production or a failed mast crop in white oaks. Red oaks may produce a good crop as frequently as 2 to 5 years, but only produce a bumper crop an average every 5 to 7 years.

The extreme variability in acorn production underscores the importance in considering alternative food sources for fall, winter, and early spring for wildlife. In most mature forests with few canopy gaps there could be as little as 50-100 lbs of deer selected forage per acre in the understory. However, with some management, like thinning and prescribed fire the amount of deer selected forage can be increased to almost 1000 lbs/ac! Additionally, forest management also increases the amount cover throughout the year for species like white-tailed deer, wild turkey, ruffed grouse, woodcock, and many forest songbirds. Contrary to popular belief, cover can be more of a limiting factor for many wildlife species compared to food availability. Forest management could include girdling undesirable trees to expand growing space for mast producing trees or conducting a timber harvest removing undesirable trees and poor producing oak trees while retaining good producing trees. For more information on conducting a timber harvest for wildlife on your property contact a professional wildlife biologist or professional forester in your area.

When spending time in the woods this fall, take the time to look up and down to see which oaks in your woods are the best producers.

Resources:
Native Trees of the Midwest, The Education Store, Purdue Extension’s resource center
Masting Characteristics of White Oaks: Implications for Management, University of Tennessee
Wildlife Biologists, Indiana Department of Natural Resources (IDNR)
Find a Forester, Indiana Department of Natural Resources (IDNR)
Enrichment Planting of Oaks, The Education Store
Forest Improvement Handbook, The Education Store
The Hardwood Ecosystem Experiment: Indiana Forestry and Wildlife, The Education Store

Jarred Brooke, Wildlife Extension Specialist
Purdue University Department of Forestry and Natural Resources