Renae Schmitt (2000)
Renae Schmitt (2000)- The association between Brown-Headed Cowbird foraging and ungulate grazing on native tallgrass prairie (Mentor: Jack Cully)
The Brown-headed Cowbird (Molothrus ater) is a brood parasite whose historic breeding range was located primarily in the Great Plains of North America. Cowbirds often forage for insects around large grazing ungulates, such as bison and cattle. Grazing ungulates help foraging cowbirds by flushing insects from vegetation. Recent research has focused on how ungulates and habitat structure affect cowbird foraging behavior and populations. However, much of the research takes place in areas with no native prairie and focuses on the cattle-cowbird association. Since cattle and bison behaviors differ, and cowbirds evolved with bison on tallgrass prairie, it is necessary to research how cowbirds forage on tallgrass prairie with both bison and cattle. I hypothesized that bison and cattle behaviors differed significantly and that cattle grazed more than bison. Because cattle behavior would be more predictable, foraging cowbird flocks would be larger around cattle than bison. I also hypothesized that foraging flocks would be larger on cattle-grazed than ungrazed tallgrass prairie because of shorter vegetation and that foraging flocks would be larger around cattle herds than in any other area on cattle-grazed prairie. I observed bison and cattle in separate enclosures and noted the time they spent performing eight behaviors and the numbers of cowbirds in each enclosure. I performed flush counts on cattle-grazed and ungrazed watersheds and noted any foraging cowbird. I also compared the number of cowbirds flushed around cattle herds to the number flushed in areas away from the cattle herds. I found that bison and cattle behaviors did not differ significantly nor did they affect cowbird flock size. More foraging cowbirds were on cattle-grazed than ungrazed watersheds, although there were still very few cowbirds on cattle-grazed watersheds. However, there were a large number of cowbirds foraging around cattle herds, suggesting that cowbirds select grazed tallgrass prairie because of the cattle and not the shorter vegetation. Much more work needs to be done on the ungulate-cowbird association in order to gain new insights on how cowbirds select and use habitats.
