Grassland songbirds are already among North America’s fastest-declining species, but a new study led by a former Midwest CASC Graduate Fellow found that many grassland birds do not seek out cooler nesting sites, even when they are available. This is likely because of their strict habitat preferences. As temperatures rise, this may leave some species more vulnerable than others.  

The study explored how local microclimates impact nest selection in grassland birds. Microclimates are small spatial variations in temperature or moisture across the landscape, such as humid areas under dense plants or cool areas beneath shaded outcrops. Researchers first determined if the different species under study primarily selected nesting sites within their normal habitat preferences or if they would use sites in cooler microclimates in hot or dry conditions. They then assessed how the habitat conditions affected nesting success. Using fine-scale models of temperature and humidity to examine microclimates, the researchers found that while some species, such as Dickcissels and Red-winged Blackbirds, nest in dense vegetation that provides cooler, more humid conditions, many other species did not actively seek out favorable microclimates. For instance, ground-nesting species like Eastern Meadowlarks and Grasshopper Sparrows, who prefer sparse vegetation, were more exposed to extreme heat and dry conditions. Constrained by their typical nesting habitat, these specialized birds experienced lower nesting success as temperatures increased, while generalist species fared better due to their ability to nest in a wider range of habitats.

This study highlights the importance of conservation strategies that address both climate change and habitat limitations of different species. While maintaining diverse microhabitats can help buffer some species from the effects of climate change, specialist species with strict habitat preferences may not benefit equally from this approach.