Dairy pastures and hayfields provide important habitat for several grassland bird species
of conservation concern, and farm management can have a substantial impact on
populations of these species. Understanding the value of rotational grazing to grassland
birds may reveal new opportunities for bird conservation, and may clarify the degree to
which this management practice can enhance agricultural sustainability. We evaluated
management practices (e.g. grazing intensity) and habitat variables (e.g. land cover) at
100m and 1200m radii on 53 dairy farms in Wisconsin, Pennsylvania and New York, in
order to assess whether rotational grazing farms supported substantially higher
abundances of three grassland bird species – Savannah Sparrow, Bobolink, and
Grasshopper Sparrow -- than other dairy farms. We conducted 2-way ANOVAs in SAS
(9.2) to examine differences in relative abundance among states and farm types using PROC GENMOD. Additionally, we modeled relative abundance as a response to Julian
date and land cover at 100m and 1200m radii using PROC GLIMMIX. Abundances of
each grassland bird species did not differ significantly among farm types. Responses to
land-cover variables differed among species but demonstrated that relative abundance
was positively associated with the proportion of hayfields and pastures in the surrounding
landscape, and negatively associated with woody cover. Savannah Sparrows and
Grasshopper Sparrows each showed a significant response to at least one habitat variable
at the 1200m scale. Our results suggest that differences in abundance of grassland birds
among farm types are modest at best, and that the impact of management practices on
these species must be understood in the context of the surrounding landscape. Our data show that grassland birds can benefit from increases in the total area of pasture and
hayfields on the landscape, which could be provided through broad adoption of rotational
grazing. However, the benefits provided by increasing grassland habitats on a small
number of farms are unlikely to have a substantial impact on bird populations,
particularly in the context of a highly fragmented agricultural landscape. Future research
for conservation planning and policy development should focus on the landscape scale
(i.e. ! 500 ha) to ensure that conservation actions are most effective.
University of Minnesota M.S. thesis. April 2011. Major: Fisheries, Wildlife and Conservation Biology. Advisors: Nicholas P. Jordan and Todd W. Arnold. 1 computer file (PDF); vii, 39 pages.
Clower, Kathryn Marie.
Effects of rotational grazing on grassland songbirds on U.S. Dairy farms..
Retrieved from the University of Minnesota Digital Conservancy,
Content distributed via the University of Minnesota's Digital Conservancy may be subject to additional license and use restrictions applied by the depositor.