Last week our grassland birds were on an epic journey north to Wisconsin. They made this monumental trek to gain access to the huge flush of productivity that occurs in the northern spring and summer. This food bonanza will make raising a brood a hungry chicks easier, and makes the hard migration worth it in the long run.
So what happens to our birds after they arrive back in Wisconsin? They search for habitat and work towards setting up territories.
We know that grassland obligate birds require grassland habitat during their breeding season; they cannot nest in any other type of habitat. However, all grasslands are not created equal, and many of these birds have strong habitat preferences. Where we may see a fairly uniform swath of grass, birds are able to pick out very distinct patches of habitat -- some that they avoid, and some that they gravitate towards. Try to think of grasslands more like a forest: with a canopy of tall grasses, an understory of flowering forbs, and a litter layer of dead vegetation from years past. Just like a forest, grasslands are not typically a homogenous stand of grass. There are clearings with no canopy layer, or areas that are denser than others. It is within these patches that grassland birds find their homes.
Many birds have strong preferences for vegetation structure. Grasshopper sparrow and upland sandpiper are both species that nest in short grass habitat. They prefer habitat without much standing dead vegetation or dead grasses laying on the ground (litter layer). They often build their nests directly on the ground next to a clump of live vegetation. These birds require habitat that is managed regularly with either prescribed burning or mowing to remove old, dead vegetation.
Savannah sparrow, bobolink, dickcissel, and eastern meadowlark all nest in mid-grass habitat. These are the species that you can find in just about any grassland habitat. Since they fall in the middle of the grass habitat spectrum, there will likely be patches that they can use in any grassland.
Henslow’s sparrow are at the far end of the vegetation spectrum. They build their nests in clumps of dead grasses remaining from past seasons, and therefore require tall grass prairie with a thick litter layer. They will not nest in a prairie that has been burned within the last year, as there will not be enough of a litter layer to suit their needs.
For some bids, the amount of grass on the landscape is equally, if not more, important than vegetation structure. These area-sensitive species like northern harrier and upland sandpiper require 250 - 500 acres of contiguous grassland, which are hard to find in Wisconsin’s fragmented landscape. Prairie chickens, which nest in central Wisconsin, are also area-sensitive. Treelines or houses disrupting the horizon my deter these birds from nesting in smaller grassy patches. The SWGSCA (Southwest Wisconsin Grassland and Stream Conservation Area) in southwest Wisconsin is trying to manage for grassland habitat on a landscape level. The DNR currently protects 12,000 acres of grassland within the project area, and is working to create wonderful habitat for grassland birds.
The next time you’re visiting your favorite grassland, try to view it as a bird would. Get down on one knee and observe the litter layer. While you’re down there, look up at the canopy of tall grasses. Think about what it would be like to search for food while hopping along on the ground beneath all of that vegetation. I hope this helps you to see grasslands through a new lens, and gives you more insight as to how neat these birds are.
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This summer, to celebrate Year of the Birdand 100 years of bird conservation under the Migratory Bird Treaty Act, we’ll be posting regular articles about grassland bird nesting ecology. My M.S. thesis focused on grassland bird nesting ecology, and I’m excited to share my knowledge—and stories from the field- with you! We’ll go into the nest to learn about chick behavior, adult sleep habits, feeding and fledging. We’ll discuss predation and learn about how adult birds respond to different predators. You’ll get to see beautiful photos of nests, eggs, and chicks, as well as video footage straight from the nest! Best of all, the next time you’re out hiking in your favorite Wisconsin prairie, you’ll feel a bit closer to the birds you love.
If you’re interested in reading more and can’t wait for the next post, you can read more about my thesis work here.
Stay tuned for our next edition of Into the Nest, coming soon!
Written by Carolyn Byers, Madison Audubon education director