We are now entering the peak season for birders, the time when you can see more kinds of birds than at any other point in the year. The statewide Spring Bird Count takes place this Saturday, and the really serious listers are thinking about Big Days. A Big Day is a marathon. To do one in the proper style, you start at midnight and bird for at least 20 hours straight, looking at each bird only long enough to identify it and then moving on.

Those of us who follow the sport in a slightly less obsessive way will be looking for hot spots–places where geography and weather combine to concentrate large numbers of migrating birds. Most of these hot spots are predictable. Montrose Harbor, for example, and Wooded Island in Jackson Park are productive year after year.

Sometimes a good place really heats up and becomes, for a time, a great place. Waukegan Beach has been like that for the past couple of weeks. That small stretch of lakeshore has produced a Sandwich tern, piping plovers, a great black-backed gull, a Franklin’s gull, a Wilson’s phalarope, a marbled godwit, flocks of willets, and a half dozen turkey vultures.

Having just returned from Arkansas, I’m not as excited about turkey vultures as I might otherwise be. Down there you can hardly look at the sky without seeing at least one of the big scavengers. The locals call them Ozark eagles.

Some people find vultures loathsome. Their diet is, after all, a mixture of shit and rotten meat. There is a widespread belief that nothing is low enough to eat a dead buzzard. (Buzzard as a word for vulture is an Americanism. In England the word is applied to soaring hawks like our red-tails.) This disgust is by no means universal. From the condors of the Andes to the griffon vultures of Egypt, soaring scavengers have been revered as symbols of divinity. It’s a logical idea, if you think about it. Here is an animal that hangs in the sky all day, watching the earth with an all-seeing eye. And when you die, it comes down and, in a most literal way, collects you and carries you off. William Faulkner admired buzzards so much that he once declared that if there was anything to reincarnation, he wanted to come back as a vulture. It’s a good life, he said. You perform a useful function, and nobody bothers you.

Vultures are nicely adapted to their way of life. Their naked heads allow them to reach into a rotting carcass and pull out an internal organ without getting their feathers gunked up with rotten stuff. Their digestive juices are truly heroic, able to overcome bacteria that would lay us out deader than mackerel. Even cholera germs cannot survive a trip through a buzzard’s intestines. They also seem to make a point of shitting on their own feet, a practice that may transfer some of that antibiotic effect to their talons and may also help keep them cool on hot days.

They are wonderful fliers, able to hang in the sky all day with almost no effort. Their breast muscles are not especially strong. They need help from thermals, rising currents of warm air, to stay aloft. Their dependence on thermals makes them ideal objects of study for birders who hate to get up early. While nearly every other species is up and about at dawn, vultures sit in their roosting trees until mid-morning, waiting for the sun to warm things up enough to create some thermals.

Once in flight, they are quite distinctive. They hold their wings tilted slightly upward in a shallow V rather than straight across like eagles, the only other birds of prey big enough to be mistaken for vultures. As they fly, they teeter constantly from side to side. Their heads look quite small because of the lack of feathers. From below their bodies and the forward halves of their wings are black. The rear halves of their wings are pale gray.

We have two species in eastern North America: the black vulture, which comes only as far north as the southern tip of Illinois, and the larger turkey vulture, which gets as far north as central Wisconsin. The critical difference between the two species may be the wing loading, the amount of body weight per square inch of wing surface. Black vultures are heavier, relative to their wing size, so they need stronger thermal currents to stay aloft without flapping. Turkey vultures, with a smaller load on their wings, can make do with weaker thermals, so they can live farther north. North of central Wisconsin, the role of airborne scavenger is taken over by the even smaller raven.

The California condor, the third species of North American vulture, is extinct in the wild. As recently as a century ago, this bird–one of the largest flying birds in the world–ranged from British Columbia to Baja California. It actually enjoyed a bonanza in the late 19th century. Cattle raising became a big business in California, but the cows were so far from markets that it wasn’t worth shipping them. Instead only the hides were taken for tanning and the skinned carcasses were left on the ground. For a scavenger, those were flush times. In recent decades, human encroachment and–most likely– a lack of food have combined to destroy the wild populations.

Piping plovers are not as bad off as the California condor, but they are plainly headed in that direction. The Great Lakes population of these tiny shorebirds is now considered endangered. Piping plovers are pale, sandy colored birds whose preferred nesting sites are on the beach, where they blend in perfectly with the sand. Unfortunately, humans love beaches too, so nesting piping plovers are constantly subject to being run over by dune buggies or squashed by leaping volleyball players.

When Edward Nelson published Birds of Northeastern Illinois in 1876, he described the piping plover as a “Very common summer resident along [the] lake shore, breeding on the flat, pebbly beach between the sand dune and shore. Arrives in the middle of April and proceeds at once to breeding.” By the 1950s it was considered an uncommon summer resident, and since 1955 there have been only six summer sight records, three from Waukegan. The last was in 1981.

Willets and marbled godwits are both large sandpipers whose appearance here in spring and fall is rare but regular. Great black-backed gulls have become regular winter birds, but we normally expect them to be gone by this time of year.

Franklin’s gull is a bird of the prairies, a common nester in pothole marshes out on the plains. We expect to see a few wanderers every fall, but spring sightings are somewhat more special.

The Sandwich tern is a really extraordinary sighting, one of those special events that can make your whole year if you are a birder. Range maps for the species show it living exclusively along the coast of the Gulf states and on both coasts of Florida. Scattered sightings have been recorded along the Atlantic shore as far north as Long Island, but the bird is almost never recorded inland. According to Steve Mlodinow’s Chicago Area Birds, nobody has ever before reported a Sandwich tern from the Chicago area.

The bird is a medium-sized tern with a wingspan of just under three feet. It has a shaggy black crest that contrasts with its white body. Its feet are black and its bill is black with a yellow tip. Our usual tern species–common, Forster’s, and Caspian–all have beaks in shades of red and orange.

Its name comes from Sandwich in Kent, England, where the type specimen was taken, and its nesting and winter ranges extend over parts of five continents. Seeing a Sandwich tern in Waukegan is probably a once-in-a-lifetime experience. There has never been one seen before; we may never see another.