Alexandra Latham (1999)
Alexandra Latham (1999)- Brown-headed Cowbird parasitism rates on ground nesting birds of the tallgrass prairie in bison-grazed and ungrazed habitats (Mentor: Jack Cully)
The Brown-headed Cowbird (Molothrus ater) is North America's best known obligate brood parasite. It is believed to have coevolved with bison, which played an important role in the existence of the cowbird by disturbing insects from the ground cover, on which the birds could feed. The Dickcissel, the Grasshopper Sparrow, and the Eastern Meadowlark are common grassland hosts of the cowbird. We hypothesized that nests of the three species would exhibit higher rates of cowbird parasitism in bison-grazed than in ungrazed habitat. The study was conducted between 6 June and 19 July on Konza Prairie Research Natural Area, in the Flint Hills, northeastern Kansas, where bison graze approximately 1,000-ha of the research area. Sixty-six nests were located. Rates of cowbird parasitism were higher for all host species in the bison-grazed area than in the ungrazed area. Rates of parasitism for all species grouped together were significantly different between sites. Results indicate that parasitism may be enhanced by shorter and less dense grass, characteristic of bison-grazed habitat, which improves the probability of locating host nests. Further studies would be valuable to determine the importance of these two factors.
