Northern Prairie Wildlife Research Center
There were seven basic land-use treatments applied to three habitat types. Treatments for annually tilled cropland habitat included standing crop, standing stubble, mulched stubble, and summer fallow. Treatments for either native mixed-grass prairie or seeded grasslands included grazing, prescribed burning, and idling or nonuse.
In this paper, grazed refers to habitats subjected to a month or more of livestock grazing at some time during the year. Grazing usually occurred between April and November for various lengths of time. Burned refers to habitats subjected to a rotation of periodic prescribed fires with intervals of nonuse between fires. For example, a field burned in 1971, rested during 1972-74, and burned again in 1975 was referred to as burned for the entire period 1971-75. A major problem with published fire and duck nest success data is the lack of a term for an area that is no longer being burned and is going into nonuse; thus, the reason for our definition of burned. Idle refers to habitats that were not grazed by livestock, burned, or tilled for usually more than 5 years in succession. These habitats were open to use by native wildlife and, except for an occasional trail, there were no visually obvious wildlife use effects.
Height, density, and rankness were recognized as important vegetative characteristics of quality nesting cover. We used poor, fair, good, and excellent as a subjective method of rating the quality (Kirsch and Higgins 1976) of cover surrounding each nest. Poor cover included bare summer fallow fields, overgrazed pastures, feedlots, mulched stubble fields, mowed areas with little or no regrowth, and brush clumps with no understory vegetation. Most cover was 15 cm or less in height. Such areas provided little nesting material and probably no barrier to predator movements. Fair cover included fields of standing stubble, moderately grazed pastures, mowed areas with heavy regrowth, brush clumps with some understory vegetation, and vegetation on poor soils. Most cover averaged 15-30 cm in height. Such areas provided thin, uniform nesting cover or scattered clumps of fairly dense cover but little barrier to predator movement. Good cover included lightly grazed pastures, undisturbed vegetation on some sites, and brushy clumps with grassy understory. Such areas provided large expanses of nesting cover with only occasional openings or paths, and offered a moderate deterrent to predator movements. Excellent cover included stands of tall-grass or grass-forb mixtures on good soils. Most cover was taller than 60 cm. Such areas provided heavy cover with no paths, roads, or trails and only scattered small openings, and possibly offered a barrier to some mammalian predator movement.