Abstract

To reduce blackbird (Icteridae) damage to field crops in the north-central United States, dense stands of cattail (Typha spp.) are thinned with glyphosate herbicide. The stands become unusable as roosting and loafing sites, which helps to protect susceptible crops nearby, particularly sunflower (Helianthus annus). Landscape-level impacts of cattail management on non-target avian species have not been studied. We measured use of upland breeding territories by male ring-necked pheasants (Phasianus colchicus) following cattail reduction in wetlands used by pheasants for overwintering. In August 1992, glyphosate was applied to all wetlands with ≥ 70% cattail coverage in four 23-km² study blocks in south-eastern North Dakota. Four other blocks were used for controls. Habitat use was inferred from territorial crowing counts. No treatment effect or treatment*year interaction (all P ≥ 0.05) was evident during 2 years of post-treatment observations. Although the herbicide eradicated large contiguous stands of cattail that pheasants had used for winter cover, surface water levels rose in 1993, which created additional cattail growth in untreated wetlands within the blocks. The additional cattail may have lessened the effect of the herbicide treatments. During drier periods, when cattail growth slows, cattail reduction could affect use of upland breeding sites. We recommend more research to assess the effects of glyphosate during drier periods.