Bird Use of an Experimental Strip Intercropping System in Northeast Iowa

Abstract

Avian use of an experimental strip intercropping system was evaluated in 1992-93 by censusing birds along transects, observing birds from tower blinds, and monitoring the outcome of nests. Thirty-five bird species were observed using the strips, with brown-headed cowbirds (Molothrus ater) and vesper sparrows (Pooecetes gramineus) most abundant. Feeding was the most common behavior, and corn and soybean strips were used most by birds. Four species of birds nested in the strip intercropping system, although only vesper sparrows nested in 1992. One vesper sparrow nest successfully fledged young. The 40 remaining nests were lost because of desertion (5% of all nests) or destruction by farm implements (39%), predators (29%), brood parasitism (12%), weather (5%), or observor (3%). Corn and soybean strips were preferred for nesting by birds. Bird abundance was higher in the strip intercropping system than in conventional row crop fields, suggesting better foraging habitat in the strips. This system, however, may function as an ecological trap for birds by attracting them to nest in an area with high risk of nest failure.