The birds are beginning to settle down at Somme Woods. Somme is the Cook County forest preserve in Northbrook where I have been working with three other volunteers on a survey of nesting birds.

We started the survey in early March, when the only birds around were year-round residents like downy woodpeckers, black-capped chickadees, cardinals, and crows. Since then we have been watching the migrants come in. The first wave included red-winged blackbirds, grackles, robins, and song sparrows, all of which arrived in the first part of March. Later that month we saw our first flickers, woodcocks, and eastern meadowlarks.

The pace picked up in April, with brown thrashers, towhees, and field sparrows among the arrivals. Also, the numbers of blue jays and goldfinches increased through the month.

In March and April we also had several sightings of bluebirds and were hoping they would stay to nest, but it has been more than a month since we last saw one. Apparently the birds we had been seeing were migrants.

We have always had the much-despised European starling, an alien species, nesting at Somme, but this year starlings are moving into parts of the preserve where they had not nested before. Starlings are hole nesters, and one of the reasons bird lovers don’t like having them around is that they are very aggressive in going after choice nest sites, often driving away native birds. So far this year we know of one pair of flickers evicted from a nest hole by starlings, and Bill Valentine and Bev Hansen, two fellow volunteers, saw starlings driving our only known pair of hairy woodpeckers out of their nesting hole.

May brings the final wave of our nesting population. The migrants that wintered in the tropics arrive just as the opening leaves trigger the hatching of spring’s first crop of caterpillars. We now have house wrens singing furiously. I have heard the wheezy, flatulent, two-note song of the blue-winged warbler. Yellow warblers and yellowthroats are singing in the brush, indigo buntings from the treetops. A wood pewee is once again singing from the lower branches of the oaks in Vestal Grove. Northern orioles are building nests.

We also have our first young of the year. On May 11 I saw a female mallard with 13 downy, flightless young swimming on the shallow pond we call the Prairie Pothole. I’m worried that our monthlong drought may dry up the pond before the young are mature enough to fly.

And there certainly are predators around waiting to grab anything helpless. Bev and Bill went to check on a crow’s nest we had found some weeks ago and discovered a fat raccoon curled up asleep in the nest. It seems safe to say it ate the eggs or young before settling down for a nap.

Several of the robins’ nests we located have also been destroyed. Robins seem totally unconcerned with concealment. Their general attitude is “Hey, look at me. I’m building a nest.” Orioles sometimes act that way too, but orioles build hanging nests way out at the tips of the tallest branches of the tallest trees, a place where few predators can climb. Robin nests, in contrast, are very accessible. The ones we have found so far are mostly on deadfalls within five feet of the ground. The trunk of a downed tree provides the sturdy horizontal surface these birds like, and the tangle of dead branches does provide some cover. But not very much. We found the nests by standing and watching the birds building them. I don’t think we ever got within 30 feet of them, but they were quite visible nonetheless. About half of them have been destroyed so far.

Later in the season the robins will build higher up in the trees. But the first nests of the year are built before the leaves emerge–we found our first on April 22–and standing trees provide almost no cover. The birds–and this seems typical of many species–build their nests well before they are ready to lay eggs. The nest may sit empty for a week or two before laying begins.

I found my first two cardinal nests this year. Cardinals have been singing since February, and the males seem to have well-defined territories by early April. But it was not until May 7 that I saw a female carrying nesting material. Song sparrows are equally leisurely in their approach. The males have been singing since early March, but only now are the females sitting on eggs. By contrast the very first catbird I saw this year was in the act of building a nest.

We may be able to add two species to our list of confirmed nesters this year: American kestrel and common nighthawk. A female kestrel spent the winter at Somme, and this spring we have been seeing a male about the place as well. Last week Bill and Bev saw the birds copulating, an act that moves them up from the “possible nester” category to “probable nester.”

Kestrels are another hole-nesting species, so Somme should provide them with a rich selection of possible homes. Clearing trees for potential prairie has been a major part of the restoration effort there–the larger trees are simply girdled to kill them and left standing. Natural cavities develop in standing dead trees, and of course woodpeckers dig lots more. It seems unlikely that starlings would be able to drive kestrels away from a good nest hole.

The American kestrel is Falco sparverius, a close relative of the European kestrel, Falco tinnunculus, and of the much larger peregrine falcon, Falco peregrinus. Kestrels do not hunt with the spectacular dives, called stoops, that peregrines use. Their usual method is either to perch on a high place with a good view of the surroundings or to hover over a likely spot and scan the ground for movement.

Kestrels are not much bigger than robins, so they cannot take the larger birds that peregrines specialize in–chickadees and goldfinches are as big as they can handle. They also eat mice and other small mammals and lots of insects.

The presence of predators is a sign of a healthy ecosystem. It says that energy is flowing through the system, from sun to plant to herbivore to carnivore, in sufficient quantity to support animals at the apex of the food chain. We now have red-tailed hawks and kestrels, and we think Cooper’s hawks are nesting east of Waukegan Road in a portion of the preserve we are not surveying.

I am really pleased about the possible addition of nighthawks to our list of nesting species. Nighthawks are members of a family called Caprimulgidae. The name is a Latin word meaning “goat sucker.” The Romans, with their usual acuity, believed that caprimulgids came out at night and suckled goats. Actually goatsuckers are nocturnal insect eaters that were probably attracted to goats because goats attract bugs.

The European nightjar is a goatsucker, and so are the American whippoorwill and chuck-will’s-widow. Goatsuckers, whose mouths are very large, capture their insect prey on the wing.

Nighthawks are among the birds that have adapted to city life. Their preferred nesting location is bare ground, but in the city they nest on flat roofs, especially flat roofs surfaced in gravel. This time of year you can hear them calling– the call is a nasal “peent” that sounds like the answering buzzer on the front door of an apartment building. If you hear it, look up and you should see a bird with long, narrow, pointed wings flying lazily or buoyantly.

Nighthawks don’t really build a nest. They just find a piece of ground that is to their liking and lay their eggs on it. During the day they sit very still, and their mottled brown plumage camouflages them very effectively.

At Somme we have found them in areas that have been newly cleared of buckthorn and other brushy plants. Dense buckthorn thickets cast such heavy shade that nothing can grow under them, so when a thicket is cut the ground is exposed. The seeds of prairie and savanna plants are scattered on this bare ground, but it takes a couple of years for these seeds to sprout and the plants to grow big enough to provide a new ground cover. In the meantime we could have good nighthawk habitat.

It would be useful to confirm nesting for this species. Though the birds are common all summer in the city, confirming them as nesting species requires getting permission from building owners to search their roofs–and you might have to search half a dozen buildings before you find anything.

The addition of kestrels and nighthawks to our list of probable or confirmed nesters brings us to a total of 36 species for the 150-acre preserve.