Conservation Mowing Benefits Wildlife

Landowners and managers may need to mow roadsides, field edges and waterways at some point in the annual growing season for management purposes. Without periodic disturbance (i.e. prescribed fire or mowing), trees and brush can quickly replace grass. The question is, how can you keep trees and shrubs from taking over and still maintain some habitat for wildlife?

Mowing can be an effective wildlife management tool when used to:

• Control annual weed growth when establishing native grasses/forbs.
• Control the invasion of woody stem plants in grasslands.
• Maintain fire breaks and trails (10- to 30-foot width).
• Reduce the amount of standing vegetation prior to a prescribed burn or herbicide treatment.

Mowing is an ineffective management tool when used too frequently or incorrectly as it:

• Reduces the diversity of plant species (wildlife food sources) and can become grass dominated.
• Decreases the number of potential nesting sites.
• Reduces the amount of winter protective cover.
• Decreases escape potential for wildlife species from a predator.

Mowing Recommendations

Wildlife need habitat 365 days a year, just like we need shelter year-round. The most ‘wildlife friendly’ way to mow is to always leave some cover standing to provide some areas of habitat. Consider only mowing a quarter to third of an area at any one time, and mowing some areas high, topping plants at least 12 inches above ground. Remember, not everything needs mowed every year – mow roadsides for safety at intersections and leave the rest.

Consider the timing of vegetation control.

• The best time to mow in the spring is in February and March, which allows cover to remain through the winter, offering protection from predators and severe weather.
• To benefit grassland wildlife and provide their primary nesting and brood rearing habitat, mowing during the growing season should be delayed until at least July 15. The primary nesting and brood rearing seasons for grassland wildlife extends from April 1 through August 1. It is best to mow after August 1, and the earlier the better in August. Delaying mowing until September or early October misses the peak of nesting season but does not allow areas to grow back and provide cover for the winter. If maintaining habitat for monarchs, remember they migrate in September and October so mowing in late July/early Aug leaves fresh tender regrowth of milkweed plants during migration.

When mowing as a management practice, leave plants at a height of 6 to 15 inches to provide necessary ground cover for wildlife.

Wildlife nest will be concentrated to areas within 60 feet of field edges and leaving all or a portion of the edges will spare many nests. Another practice that can help minimize killing nesting hens and young broods is to begin mowing in the center of hayfields and mow in an outward pattern, pushing wildlife to the outside of the field and reducing mortality.

Types of Mowing

Generally, mowing is used for noxious weed control, as a firebreak, as strip mowing to control woody species or to create a trail.

• When mowing for noxious weed control, limit mowing to only affected areas and raise the height of the mow blades to only remove seed heads. This type of mowing is effective during the first and second year of a new native prairie planting.
• Mowing can be effective in creating a firebreak as it keeps the vegetation short and lush, removes the build-up of thatch and helps control the height of flames near the edges of the burn area.
• Alternating mowed and non-mowed strips, called strip mowing, across an entire field can be used to control woody plants. There are some negative effects (such as mowing too frequently and reducing diversity and becoming a monoculture), therefore, utilize strip mowing only to the degree necessary to control the woody invasion.
• Trails may be mowed two or three times a year to facilitate access to the property to conduct other management activities, such as invasive species removal. Only construct enough trails to allow for management activities to take place. Do not mow everything underneath like a city park. Trails should be approximately 10 feet with surrounding native vegetation left undisturbed. Refrain from destructive use of ATVs, dirt bikes, etc.

The tall grasses and forbs in road ditches, waterways and other ‘idle’ areas are much more than ‘grass.’ These areas are ‘home’ to many species of wildlife—ring-necked pheasants, bobwhite quail, cottontail rabbits, many species of songbirds and a variety of insects that these species feed on—that have no other place to go. Predators often get the blame for causing declines in small game populations, but habitat is the primary problem.

When habitat is on the landscape in sufficient quantity and quality, game species can handle the natural losses to predators and still thrive. When all the habitat is removed, wildlife does not stand a chance. Frequent mowing is the leading cause of annual habitat loss from remaining habitat areas.

For more information, contact Bob Caveny at bob.caveny@illinois.gov.

---

Bob Caveny, of Carlinville, is the Agriculture and Grassland Wildlife Program Manager at the Illinois Department of Natural Resources (IDNR). Caveny comes to Wildlife from being the Agricultural Lands Manager within the IDNR Office of Lands. Previously, he worked as the IDNR Conservation Stewardship Program Manager in Private Lands, Illinois Recreational Access Program Coordinator for the Sangamon Soil and Water Conservation District, and as a Regional Wildlife Biologist and Farm Bill Biologist for Pheasants Forever in Indiana and eastern Illinois, respectively. He has a BS degree from Eastern Illinois University in Environmental Biology and a MS degree from Texas A&M University in Wildlife Biology. In his spare time he enjoys hunting, fishing and managing habitat.