One might imagine that the vast prairies of the middle western United States have always been there, but in the geological time scale they are relatively new, the product of global warming. The last glacial period reached its peak only about 18,000 years ago. Ice covered most of Canada and extended down into what are now the north Atlantic states and south to around the Ohio River in the Midwest.
of the age and species of pollen collected at nearby Nelson Lake
provide an interesting picture of the history of the prairie. As the ice
receded over the next 2,000 years the area around my second home in Illinois resembled present-day Arctic tundra, covered by low-lying sedges and
scattered evergreen trees. Humans crossed over to North America from
Asia via the land bridge before the oceans rose to separate the
forests then proliferated over the next 5000 years. The soil remained
moist, favoring hardwoods such as ash and elm that began replacing the
evergreens. About 11,000 years ago, as rainfall diminished, oak and
hickory appeared, and the pollen record indicates that grasslands
developed in forest openings. Beginning around 6,500 years ago, with the onset of a
3,000 year dry period, lightning-caused fires greatly enlarged the grasslands as they flourished and evolved into the
landscape that greeted the first European settlers. Following this, as
prairie was tilled and forests were cleared, exotic plant pollens
appeared. Native grasses and plants declined.
A view of the old
silo and restored tall grass prairie at the east entry of the Nelson
Lake Marsh/Dick Young Forest Preserve, Kane County, Illinois. Ahead, a
woodland borders the east shore of the lake.
There are wetlands along the southern and western edges of the lake, as well as in several potholes.
extend to the north and west of the lake. These 800 acres of former
crop and grazing lands are actively managed by mowing and controlled
burns to restore them as nearly possible to their original condition. In
fall the grass turns a golden brown and is a rich source of seeds for
Over the course of the seasons, the diverse habitat attracts a stunning variety of bird species, from the large...
...to the small.
Sandhill Cranes breed in the wetlands.
A Cooper's Hawk soars overhead. The prairie suddenly falls silent.
are among my favorite photographic subjects. Catching them out in the
open and in good light requires patience (and I must admit that at my
age I don't mind the opportunity to rest a bit while I wait). Several
species of sparrows breed in the grasslands and marginal savannas. Song
Sparrows are most abundant.
Savannah Sparrows often forage on the trails.
Grasshopper Sparrows are less often seen out in the open. Their numbers
seem to depend upon the availability of short grass in areas that had
been recently mowed or burned.
A few Henslow's Sparrows breed in the prairie in small clusters.
The habitat requirements of this threatened species are very demanding, as
they will not build a nest in a recently cleared area. Henslow's
Sparrows select nesting areas that have a couple of years of dead grass
litter accumulated on the ground. They abandon the site after two or three years, when taller weeds and saplings start invading. They also require an
expanse of tall grass prairie surrounding their breeding areas, and
will not nest in fragmented habitat.
Sparrows are more often heard than seen, as they sneak through the
grass like mice. They look as if they are putting great effort into their
song, which comes out sounding like little more than a squeak.
Field Sparrows prefer the woody edges of the prairies.
Swamp Sparrows build their nests in the marshes.
Chipping Sparrows are most commonly found in the woodlands.
Among the non-breeding sparrows, I have seen a few Lincoln's Sparrows.
Sparrows invade as winter approaches, and stay until spring. (This
photo is my favorite of the species. I took it in Alaska. All the other
images are from the Nelson Lake area.)
White-throated Sparrows favor the shrubby margins of the woodlands.
Fox Sparrows can be elusive, rummaging through the ground litter or hiding in the trees.
This [I thought was] is the only Clay-colored Sparrow I have ever seen at Nelson Lake. [See Steve's comment below. The corrected identification is Swamp Sparrow-- sorry about that, but in the field its light breast and dark "mask" led me astray, not to mention the fact that it was in a thicket out on the prairie. Ken]
Now take a good look at this-- will you ever again call sparrows just LBJs*?
* "Little Brown Jobs"-- NOT
Search archives of ROSYFINCH.COM