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USD Biologists Predict Changes in Grassland Bird Numbers Due to Climate and Land Use

A lark bunting bird sitting on a barbed wire fence. The bird is small and mostly black with one white stripe on the wing. The lark bunting is one of the 24 grassland bird species studied by USD biology professors David Swanson and Mark Dixon.

VERMILLION, S.D. – With support from the National Science Foundation, University of South Dakota biologists analyzed data to show how future shifts in land use and changes in climate will impact grassland birds in a section of South Dakota, North Dakota, Wyoming and Montana known as the Upper Missouri River Basin.

Over the past century, about half of the grasslands that once covered the Great Plains of North America have mostly been converted to cultivate crops and graze cattle. The loss of this rich ecosystem affects wildlife in the region. Grassland birds such as the western meadowlark and the bobolink, for example, have experienced a population drop of more than 40% in the last 50 years.

Despite past declines due to the loss of habitat, future changes—including a warming climate—may increase numbers of certain grassland birds, according to USD biology professors David Swanson, Ph.D., and Mark Dixon, Ph.D., co-investigators on the study with Andy Baltensperger, Ph.D., a former USD post-doctoral researcher now at the University of Alaska.

The researchers used field bird survey data from the Bird Conservancy of the Rockies and climate and land-use scenarios spanning a range of future possibilities developed by the U.S. Geological Survey. They projected changes in population abundance for 24 grassland bird species using 20 climate and landscape variables, such as winter and summer temperature, elevation and land use changes associated with different scenarios of biofuel cultivation.

The researchers found that most of the species will increase their numbers in many of the future scenarios, though some, like the lark bunting, show a population decline. Birds in the southeastern section of the area studied are more likely to be affected by the rise in temperatures due to a decline in food supply. Swanson said that many birds may move to a habitat in higher elevation because of the rise in temperature.

“Overall, we found that climate change was a more important predictor of future bird abundance than land-use change, perhaps because most land-use change has already happened, but also because broad-scale shifts in suitable climate likely outweigh smaller-scale land-use change,” Swanson said.

The researchers published the findings of this study in the August 2020 issue of Landscape Ecology.