Birds at Midewin

Upland Sandpiper

The Birds of Midewin

In the past 25 years grassland bird populations have declined more than any other group of North American birds.

Midewin is famous for grassland birds, a group of birds that is imperiled in North America because of habitat loss.  Although most people come to see the grassland birds, wetland, shrubland, and woodland birds can also be seen at Midewin in appropriate habitats.

Many grassland birds have specific habitat requirements regarding size of habitat and structure of vegetation. During the Joliet Arsenal decades, the Army leased to local farmers all the land that served as buffer for the TNT manufacturing plants. These extensive pastures, hayfields, and other grasslands provided both the area and diversity of habitat structure to meet the needs of many species of grassland birds.

Grassland birds can be placed into three suites;

those that prefer short-stature grasses,

those that prefer medium-stature grasses and

those preferring tall-stature grasses. Species do overlap the three general suites, but each seems to do best in one of the suites.

The continuing management challenge at Midewin is to maintain the different habitat structures preferred by different grassland bird species. Species do overlap the three general suites, but each seems to do best in one of the suites.

As grassland habitat restoration and improvement continues, populations of wetland birds and woodland birds should also improve.  Some common shrubland birds may decrease in population numbers as invasive non-native shrubs are controlled, but some habitat will remain for the rarer shrubland birds such as Bell’s vireo and yellow-breasted chat.

 

Killdeer (Charadrius vociferus)Short-stature Grasslands

The most critical grass habitat at Midewin is short-stature grasslands.

Midewin uses cattle grazing to provide short-stature grass habitat. Hay mowing and idle pastures provide the mid-stature grass habitat, while prairie reconstructions and other non-grazed areas provide tall-stature grass habitat.

The lands at Midewin have a long history of cattle grazing, especially the area west of Route 53.  In much of that area, plowing for crops was not feasible because the dolomite limestone is so close to or even at the surface.  Instead, the farmers used the area for pasture, and that practice was continued on buffer lands while the Army administered the Joliet Arsenal. 

Grass height is monitored during late spring and early summer to determine if the proper habitat structure is being maintained. Tall-stature grasslands don’t differ much from year to year and are given a much lower priority for monitoring.

Grazing tracts are measured more than non-grazing tracts to help determine the proper number of cattle needed to achieve the desired results. The Robel pole method is used to determine grass height.

Another component of habitat structure is the amount and location of shrubs and trees within the grasslands. Most grassland birds require wide-open areas with few to no shrubs and these areas are often referred to as “unfragmented” habitat. The Loggerhead Shrike prefers short-stature grassland with some shrubs for nesting.

When areas at Midewin were unfragmented by removal of woody brush and small trees, small groupings of shrubby trees are left for Loggerhead Shrikes along the perimeter. Approximately one-half of the Loggerhead Shrike nests found each year at Midewin are located in these small areas of shrubby trees on the edges of unfragmented tracts.

 

Upland Sandpiper (Bartramia longicauda)The Upland Sandpiper

As the huge herds of bison roamed across the central grasslands, eating and leaving behind huge swaths of disturbed prairie with short vegetation, the Upland Sandpiper made its home in their wake.  Today Upland Sandpipers are listed as endangered in Illinois and as a Regional Forester Sensitive Species. 

The large acreage of short-stature grassland habitat at Midewin supports the state’s largest population of Upland Sandpiper and some of the largest breeding concentrations of grassland birds in Illinois, especially Upland Sandpipers and Bobolinks.

 

Nesting and Habitat

Upland Sandpipers will only nest on a large grassland, and only if the vegetation is shorter than the bird is tall.  When the bison disappeared, the Upland Sandpiper adapted to nesting on large cow pastures in tallgrass prairie regions, and continued to nest in natural shortgrass prairie further west. 

As agriculture changed in Illinois from mixed farming with hayfields, pastures and cropland to the current corn-soybean rotation, Upland Sandpipers nearly disappeared from the state. 

In 1982, several biologists from the Illinois Department of Natural Resources attended a meeting at the Joliet Army Ammunition Plant. While there they noticed upland sandpipers sitting on utility poles. 

Since upland sandpipers were rare in Illinois and listed as endangered by the Illinois Endangered Species Protection Board, attempts were begun to open up the ammunition plant to a survey of upland sandpipers. The Army allowed limited surveys on the manufacturing (west) side in 1983 and 1984. 

The surveys showed good numbers of upland sandpipers, representing the largest population in the state.  From these early surveys it was obvious that the livestock grazing tracts at the ammunition plant were home to most of the upland sandpipers. 

Starting in 1985, expanded surveys began to cover all grazing and hay fields at the ammunition plant, approximately 5,000 acres, and to look for all grassland birds.  It soon became clear that the ammunition plant was one of the most important grassland bird areas in the state, perhaps in the Midwest. 

 

Indigo Bunting (Passerina cyanea)Midewin’s Role in Grassland Bird Recovery

As grassland habitat is lost to suburban housing, commericial/industrial development, and corn or soybean crop fields, Midewin provides a refuge for many grassland birds. Midewin provides perhaps the last opportunity in this region to create relatively large grasslands for several threatened birds, including Bobolink and Loggerhead Shrike. 

The grasslands were managed for livestock grazing under Army ownership, which was good for grassland birds such as upland sandpipers, grasshopper sparrows and loggerhead shrikes, who like short stature grasses.  Bobolinks were common in the hay fields, although early haying may have killed nestlings. 

However, since there weren’t many tall stature grasslands, several species, such as Henslow’s sparrows and sedge wrens, were very rare. 

Today the Forest Service is working hard to improve habitat at Midewin for upland sandpipers and other grassland birds that prefer short grasses, as well as for grassland birds that prefer taller grass structure. 

One effort that has been made was converting crop fields to grazing tracts and clearing brush from existing grazing tracts.  With these efforts Bobolinks and Henslow’s sparrow populations have already increased in numbers. Grasshopper sparrows, while declining nationally, are doing well on Midewin and Loggerhead shrike numbers, while not increasing, are also not declining.  And ecologists hope that, over time, the population of upland sandpipers will also increase. 

The future is bright for grassland birds at Midewin.