Wildlife Use of Experimental Intercropping Systems

Wildlife Use of Experimental Intercropping Systems

Summary

Rationale:
Agricultural cropland constitutes most of the habitat available to wildlife in the Midwest. Some
of these habitats have proven to be "ecological traps" for birds where productivity is well below
levels necessary to sustain populations. Strip intercropping systems may improve habitat
conditions for wildlife in agroecosystems.

Objectives:
1) Document bird and small mammal abundance and species composition in an experimental
strip intercropping system.
2) Determine preferential use of various crop strips by birds and small mammals.
3) Assess avian nesting success and productivity in the strip intercropping system.

Methods:
Bird use of experimental strip intercropping systems was evaluated in 1992 and 1993 from tower
blinds, censusing along transects, and searching for nests. Small mammals were evaluated by
using Sherman live-traps.

Results:
Thirty-five bird species were observed with brown-headed cowbirds and vesper sparrows being
the most abundant. Foraging was the most common bird behavior observed, and soybean and
corn strips were preferred for use by birds. Four species of birds nested in strip intercropping
systems, although only vesper sparrows nested in 1992. Only 2.4 percent of vesper sparrow nests
successfully fledged young. Remaining nests were destroyed by cultivation or planting activities
(39.0 percent), predators (29.3 percent), brown-headed cowbird parasitism (12.0 percent),
weather (4.9 percent), desertion (4.9 percent), or observer error (2.4 percent). Two nests had
unknown outcomes. Six small mammal species were captured, although 94.3 percent of all
animals were deer mice. Deer mice prefer oat strips before oat harvest and soybean or corn strips
after oat harvest.

Conclusions:
Bird species diversity and abundance is high in strip intercropping systems, suggesting better
foraging habitat than conventional row crop fields. These systems, however, provide ecological
traps for birds by attracting them to nest in a poor production area. Small mammal diversity in
strip intercropping systems is low, although greater structure might provide attractive habitat for
a greater period of the growing season than in conventional row crop fields.

Farmer Adoption and Direct Impact:
Forty percent of all nests found in strip intercropping systems were destroyed by farming
implements. It is recommend that farmers wishing to increase avian production on their land
reduce the number of times machinery passes through their fields, and wait at least one month
between passes.

Information Products:
Journal Article: "Bird Use of an Experimental Strip Cropping System in Northeast Iowa". H.R.
Stallman, L.B.Best. Journal of Wildlife Management vol. 60, pp.354-362.