Date of Award

December 2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biology

First Advisor

Susan Ellis-Felege

Abstract

Cattle grazing is one of the main economic contributors driving grassland ecosystem existence across the landscape. Cattle grazing can impact a variety of aspects of grassland ecosystems functions, including which wildlife species use them and in what ways. Given the drastic declines in grassland passerines, it is especially important to understand how different grazing practices affect critical population metrics such as reproductive success, clutch size, and number of fledglings. There is a wealth of research on grassland passerine reproductive in response to grazing systems throughout North America; however, most of the existing literature studies more traditional, longer rotational (LR) grazing practices with few studies in North Dakota and limited information on high intensity, short duration (HISD). In HISD systems, higher cattle densities, smaller paddock sizes, shorter durations in paddocks and longer rest periods are common characteristics that could impact habitat selection and reproductive success by birds. Moreover, because working landscapes rely on the ranchers who employ such practices, there is a need to understand how the values, intents, and motivations may influence ranchers towards different grazing practices that ultimately impact the wildlife using the grasslands. In this study, we investigated passerine use and reproductive success across 4 HISD and 4 LR sites in North Dakota during May to August from 2021 – 2023. In addition, we used semi-structured interviews to conduct a qualitative analysis of ranchers to determine the values, intents, and motivations that may set apart HISD from LR grazing practices. We found no difference in daily nest survival in passerine guilds (ground, suspended, and canopy nesting passerines) between the two grazing practices, despite differences in cattle density, duration in paddock, and paddock size. Further, we found less than 2% of all the nests in our study period over the three years were trampled, which was opposite of our initial hypotheses that increased cattle densities in smaller paddocks would have resulted in greater trampling rates. In HISD sites, we observed greater parasitism rates from Brown-headed Cowbirds (Molothrus ater), which resulted in increased daily nest survival and nest survival estimates but lower host clutch sizes and fledging success from host species compared to those metrics on LR sites. From area transect surveys conducted twice each summer, we found similar species composition with slightly more species in HISD sites than LR sites. Of note, Chestnut-collared Longspurs (Calcarius ornatus) were more numerous on LR sites compared to HISD sites. When examining vegetation characteristics between the LR and HISD sites, we found the two grazing practices ultimately had the same utilization across plots after grazing had occurred, and this likely shaped our limited differences in bird reproduction and bird use. Generally, it appeared that although ranchers were grazing in different ways, they were ultimately grazing to similar vegetation outcomes and that cattle densities were not as intense on the HISD as assumed would be the case from rancher discussions during site selection. Further, HISD ranchers in North Dakota may have intense rotations but not necessarily intense grazing outcomes. Finally, from our interviews we found that regardless of grazing practices, ranchers share a lot of values and motivations that guide their way of life. These included strong values associated with forage/grass production, a focus on their families, and the autonomy that the ranching way of life brought to them. They were frequently motivated in succession planning in their multi-generational operations. Differences were observed in intents such as HISD ranchers intended to build better resiliency in their forage/grass production through increased rest periods, which helped them battle drought. Comparatively, LR ranchers intended to ranch more simply, and not have to worry about the increased labor or costs associated with intensive grazing management like increased fencing or water availability. Future research should continue to examine vegetation outcomes to better understand specific bird species responses since grazing practices may not be reflective of the actual habitat characteristics on the landscape. In addition, surveys on average stocking rates and perceived “grazing practices” that ranchers use would help to characterize the overall grazing intensity common across the North Dakota landscape. Ultimately, by working to partner with ranchers to produce specific deliverables could be a more effective manner for conservation delivery through embracing the knowledge that exists in working landscapes.

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