Summer begins to slip away even as the sweat rolls down our faces. I began to notice the signs while at a cocktail party on Navy Pier the evening of July 25. Sipping rum and Coca-Cola, nibbling on prosciutto and melon or strips of smoked salmon wound around asparagus tips, savoring the loveliest of summer sunsets, I watched the gulls fly by. There are a lot of them, and many were clothed in very dark plumage, a mark of birds born this year. Already out of the nest and on their own, they are a sign that the rookery is breaking up, that the nesting season is over. The birds have begun the late-summer wandering that will culminate in the fall migration.

I saw three Caspian terns that evening–or perhaps one Caspian tern three times. These birds nest in colonies on islands at the northern end of Lake Michigan, so they too were wanderers who had left the nesting grounds behind.

After the party ended, as we walked the length of the pier, two immature black-crowned night herons flew by, headed out toward the breakwater. They probably came from Lake Calumet, the nearest nesting colony, and they may have been wandering north. Herons do that. Southern species –tri-colored herons and reddish egrets, for example–often are sighted in August far north of their breeding grounds.

The birders’ hot line (708-671-1522) brings news of Franklin’s gulls, birds that nested in prairie potholes in the Dakotas, seen now on Waukegan beach, along with laughing gulls that have wandered north from the Gulf coast.

Shorebirds are in full flight from their tundra breeding grounds. A dozen species show up some days at Lake Calumet, whimbrels with long sickle bills among them. We can expect the first south-bound warblers any day.

At Somme Woods Forest Preserve in Northbrook, where I have been working on a breeding-bird survey, the sense of a season ending is very strong. A few weeks ago huge flocks of young starlings just out of the nest were in clumsy flight through the preserve. Last Sunday I was scaring up equally clumsy flocks of young red-wings.

Only a few birds were still singing: a song sparrow, perhaps working on its third nest of the summer, an indigo bunting, probably nesting for the second time.

But the plants and the insects of the prairie and savanna grove had not got the news of summer’s end. Dragonflies were everywhere, as were butterflies: monarchs, crescentspots, wood nymphs, sulphurs, skippers–more kinds than I could hope to identify. And hordes of bumblebees, honey bees, wasps, and mystery bees I had never seen before.

And flowers. Flowers in profusion, in numbers I have seldom been privileged to see. Not quite 15 years ago Somme Woods was an ordinary forest preserve formed from old fields and former cow pastures. It offered some green space, some relative quiet, some room for various animals, and a refuge for a few rare plants of our native prairies and savannas.

But then, the Cook County Forest Preserve District granted permission to a volunteer organization called the North Branch Prairie Project to manage the land, to restore the prairie and savanna communities that had existed before the land was turned to cow pasture and cornfield. For 13 years now the work has gone on, tens of thousands of hours of hard labor by more than a thousand volunteers. On hands and knees searching through the weeds to gather seeds from prairie and savanna plants on the site and on unprotected and endangered land nearby, doing stoop labor cutting invading brush–buckthorn and other miserable aliens–with lopping shears and handsaws, and then raking the native seeds into the cleared ground. They fought cold and damp in March and December, endured mosquitoes and heat in June, got rained on, snowed on, sleeted on, and never stopped. Week after week they came back. Spring and fall, they came out with drip torches to burn the land, to return fire to the place it had in this ecosystem before plows and pavement came to Illinois.

And my God, the results. You don’t need to be some sort of ecological expert to know that Somme Woods is a special place now. The flowers will tell you.

I took a brief stroll around the western half last Sunday and started writing down the names of the flowers I recognized. Some I didn’t know, so this list is incomplete.

The greenish-white globes of rattlesnake master caught my eye first. Early settlers used an infusion of this plant to treat snakebite–with what results I do not know. Cattle find it quite palatable, so it disappeared from all but the best prairie remnants.

Brown-eyed susan, a daisy with yellow rays and a brown disk at the center, has become a garden plant as well as a prairie species. Yellow cone flowers look like brown eyed susans except that their yellow rays droop downward to form a cone rather than extending straight out from the disk.

The shallow pond where Canada geese swam early this spring is filled with the pink blossoms of swamp milkweed, and on the low ground all around the pond are the delicate pinks of nodding wild onion. One story on the origin of the word “Chicago” says that it means “place where the nodding wild onions grow,” or something like that. Certainly this would have been a common plant on the wet prairies of the Chicago lake plain.

The pale blue heads of the wild bergamot are scattered over drier areas, and here and there are the tall spikes of the blazing stars, their purple flowers just beginning to open.

At this point I have come maybe 100 feet from my car. I haven’t yet seen the first tiny white blooms of the flowering spurge or the rich purple prairie clover or the long slender, gracefully arching flower clusters of the culver’s root, or the white clusters of the woodland milkweed. Not to mention the grasses, the tall prairie grasses–big bluestem and Indian grass–that are just beginning to send up their flowering stalks.

What is most impressive about all this is that these flowers are not just present, they are abundant. You don’t need to search carefully through the weeds. You don’t need the trained vision of an expert to find them. You can’t miss them. There are thousands of them. They surround you.

Perhaps the most impressive place in the whole preserve is Vestal Grove (named after an Illinois botanist named Stanley Vestal and not after the vestal virgins of the Romans. Applying Old World mythology to this New World setting would be totally inappropriate). When work began on the grove, the giant old oaks that survive from presettlement times were buried in a dense growth of European buckthorn. This invasive shrub grew so thickly in the understory that you couldn’t even see the oaks.

I happened to be there on an early spring workday when the process of cutting the buckthorn from the grove began. We started in from the north edge, cutting away these dense shrubs, and I remember how amazed I was to come upon an oak with a trunk so thick my outspread arms reached barely halfway around it.

Now a path leads through the grove, and you can see the huge trunks and the enormous limbs of the spreading crowns. It is the buckthorn that is hidden now. It hangs on in the shade under a gloriously fecund growth of native savanna plants. I saw the purple flower clusters of joe-pye-weed plants taller than me, and hundreds of equally tall figworts with their strange green and brown flowers. The rich blue blossoms of tall bellflower flanked the path, and here and there I could see the flower clusters of bottle-brush grass.

None of these native savanna plants grew in Somme Woods when restoration began. The seeds were collected by hand and sown here, and the vigor of their growth reveals how completely they belong here.

The wonder of ecological restoration is that at some point, the reviving ecosystem takes over and begins to heal itself. Those bumblebees dancing through the bergamots are helping create seeds that will scatter over the prairie and grow even more bergamots.

There is still brush to be cut and invading box elders to girdle. We still have weeds such as cow parsnip and sweet clover to worry about, and more native species will be added to the system in the coming years. But for increasing areas of the preserve the ecosystem can maintain itself with nothing more than an occasional fire. At Somme the prairie and savanna have been brought back to life.