Cover Often Limits Bobwhite Numbers
Among the factors influencing the number of native quail (bobwhite present without stocking), individual landowners can probably impact quail populations the most through the management of cover.
Some aspect of cover, either too little or too much, often limits quail abundance. This is an important concept because many quail managers expend much of their efforts trying to increase quail numbers through management of quail foods. Fall and winter foods seldom limit quail abundance to the extent that cover limits quail abundance.
So, spending money and time on quail food management generally does not increase quail numbers when some aspect of cover limits quail abundance.
Management of native bobwhite populations is very challenging, often frustrating. The frustration occurs because quail managers often do not adequately identify and change the real factors that limit bobwhite abundance. Several things appear to influence the number of bobwhite naturally occurring on a tract of land. Some of these factors include temperature extremes, rainfall patterns, habitat fragmentation, grazing, fire, hunting, predation, food, and cover. Quail habitat is dynamic; weather and plant communities continually change. Changes in weather and plant communities often alter which factors limit quail numbers.
For an area to support as many native quail as possible, every bit of the area must be quail habitat. The entire area must have appropriate cover. Quail habitat includes many kinds of cover, such as loafing or resting cover, traveling or feeding cover, ground cover, escape cover, nesting cover, and roosting cover. In southern Oklahoma and northern Texas, the most limiting aspects of cover usually appear to fall in one or more of the following categories: lack of appropriate woody cover, poor distribution of appropriate woody cover, excessive woody cover, lack of herbaceous cover, or excessive thatch (ground cover). Herbaceous refers to plants that do not have woody stems. All grasses, grass-like plants, and forbs are herbaceous plants. Forbs are broadleaf or nongrasslike herbaceous plants.
Woody cover provides protection from summer heat, cold winter winds, and predators. Some woody plants also provide food. Woody cover typically provides most of the loafing and resting cover as well as some of the traveling, feeding, and escape cover.
The amount of woody cover necessary for optimum quail habitat depends on the quality of local herbaceous cover. Quail need less woody cover when high quality herbaceous cover is abundant. Dr. Fred Guthery, Oklahoma State University Bollenbach Chair in wildlife management, says openings should not exceed 50 yards wide when herbaceous cover is relatively poor. With abundant high quality herbaceous cover, he says open spaces between woody cover can be as wide as 150 yards. As opening size increases beyond this point, the area supports fewer quail.
Distribution of woody cover is as important as overall abundance. Optimum quail habitat should have woody cover well distributed throughout the whole area. When woody cover is clumped into only a few patches, an area supports fewer quail than if it is well distributed throughout the area.
Woody cover can be excessive. Quail need open areas, too. Optimum woody cover for bobwhite varies from 10 percent to 60 percent of the landscape depending upon the amount of herbaceous cover. An area completely covered with brush or timber, or even two-thirds covered with woody vegetation, supports fewer quail than an area with a better balance of woody cover and openings.
Quail woody cover should be dense overhead and along the sides with the ground surface relatively open underneath. Most woody plant species can provide adequate quail cover during some growth stage. Many tree species, such as post oak or loblolly pine, provide adequate quail cover only during their young shrubby growth stages. Some woody species, such as sand plum and lotebush, provide excellent woody quail cover throughout much of their lifespans. To provide good quality quail cover, most patches or clumps of woody plants should cover at least 75 square feet.
Forbs and grasses provide herbaceous cover. Herbaceous cover allows quail to feed and travel without detection by predators or excessive exposure to sun and cold. It provides nesting cover, roosting cover, and escape cover from predators. Forbs and grasses provide most of the insects and seeds that quail eat. Ideally, herbaceous cover should be dense enough overhead and laterally to hide quail from predators and weather extremes while open enough underneath to allow quail relatively unrestricted movement across the landscape.
The quality of herbaceous screening cover on an area fluctuates due to changes in seasons, rainfall, grazing, burning, mowing, tillage, fertility, and spraying herbicides. For example, a robust stand of common broomweed provides excellent screening cover in the fall, but provides no screening cover when the site is mowed or tilled. Since herbaceous cover changes and can be inconsistent, it is probably better to manage for smaller opening sizes (closer to 50 yards rather than 150 yards) and relatively abundant woody cover (closer to 40 percent rather than 10 percent) to buffer changes in herbaceous cover.
Plant material covering the ground surface is called thatch. Excessive thatch interferes with quail feeding and traveling. Excessive thatch exists in lush bermudagrass. It can be a problem in other grass pastures when they are ungrazed or unburned for more than a year. Optimum quail habitat requires annual disturbance such as grazing, burning, or tillage to manage thatch.
Even though other factors influence quail numbers, management of quail cover seems to provide us the most power to increase naturally occurring bobwhite populations. With the best managed habitat, bobwhite numbers are higher, but continue to fluctuate in response to weather factors that we cannot control. Cover is probably the most limiting aspect of bobwhite habitat that we can change.