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Field & Street

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Spring arrived officially at the beginning of this week. As is usual in Chicago, its arrival was signaled by snowstorms and subzero windchills and celebrated by the local inhabitants with wisecracks and lots of shivering. Even when we have an unusually warm winter, it seems we can count on a cold spring.

However, the birds are taking all this foul weather in stride, arriving, or passing through, just as they do every year. The spring migration begins at this latitude in late February and continues until early June. Temporary shifts in the weather, sudden cold snaps or freakish warm spells, seem to have no more than slight effects on the process.

Waterfowl come first. Eighteen species of ducks were reported from the Palos forest preserves last week. Tundra swans and mute swans are showing up here and there. It used to be that migrating flocks of wild geese signaled the coming of spring, but since the establishment of resident flocks of Canada geese around Chicago, we see these birds year-round. It's hard to tell whether a passing flock is on its way to Hudson Bay or just flying from an ornamental pond at a suburban corporate headquarters to the North Branch of the Chicago River.

The critical question for the waterfowl is whether the winter ice has melted from our lakes and rivers. Once the ice is gone and the birds have access to their food supply, snowstorms or short cold snaps won't bother them much.

Tundra swans have probably been passing through here on their way north since the end of the last ice age, but the mute swan is a rather new addition to our avifauna. It is a European bird, the bird that Andersen's ugly duckling grew up to be. Introduced to the U.S. in the last century as a decor item in formal parks and gardens, it is slowly expanding its range. The first established population in the midwest nested around Traverse City, Michigan, and most of the birds we have been seeing around Chicago come from that population. It is only in the past decade that it has become a regular, predictable bird in this area.

There are also a few trumpeter swans around. A captive flock lives at Underwriters Laboratories in Northbrook, and lately an immature bird of uncertain origin has been hanging around a golf-course pond in Lincolnwood. Trumpeter swans are enormous birds, the world's largest swans. A big male can weigh nearly 40 pounds and its wings can span more than eight feet. Putting one next to a Canada goose is like standing a Clydesdale next to a Shetland pony.

Until a century ago the trumpeter was a nesting species in the Chicago area, but the combination of habitat loss and hunting pressure extirpated it. In fact, the combination nearly drove it to extinction. Thirty years ago small populations in Yellowstone Park and Montana were all that remained of the trumpeter swan. Since then it has been successfully reintroduced in several areas. The Lincolnwood bird may have come from such a reintroduction in Michigan.

March is also the season for seeing all three species of mergansers. Mergansers--the name is a combination of the Latin words mergus (diver) and anser (goose) --are fish-eating ducks whose long, slender beaks are edged with a row of serrations like the teeth on a saw, a trait that figures to be helpful to a bird that needs to hang on to slippery fish.

The common merganser and the red-breasted merganser are both big birds. The common is almost the size of a chicken. We see both of these species on Lake Michigan during the winter. The much smaller hooded merganser just passes through in spring and fall. The two big species need a long runway, and therefore a big body of water, for takeoff. They patter across the water, wings beating furiously for 20 or 30 yards before they become completely airborne. The smaller hooded merganser can leap directly into the air like a mallard, and therefore can live on tiny ponds or streams.

All three species are skilled divers. They go down headfirst and swim underwater with both feet and wings. They can also control their buoyancy so precisely that they sink out of sight without the tiniest splash, or sink only their bodies and leave their heads out of water.

Aside from water birds, the other major group of early migrants is birds of the prairies and grasslands. Snow melts early on open ground that gets full sun every day, so seeds, insects, and small mammals are exposed on the prairies when woodlands are still buried in snow.

Meadowlarks began arriving about the first of March, and they are now in full song. We live on the boundary between the eastern and the western meadowlarks, although the eastern species is far more common. The two are almost identical in appearance, so their songs are the best way to tell them apart. The eastern sings a clear descending, slurred whistle. Peterson describes the song of the western meadowlark as "flutelike, gurgling, and double-noted."

Horned larks and lapland longspurs are also passing through right now. The horned lark is our only native lark, a relative of the European skylark, the bird that Shelley apostrophized as a "blythe spirit." Horned larks seem to favor the barest and least inviting of lands. Plowed fields are good places to look for them.

The lapland is one of four species of longspur--the birds are named for the unusually long claws on their hind toes--and the only one that appears regularly in the Chicago area. Longspurs are finches that feed and nest on open ground. The lapland longspurs we see here are heading for the tundra where they will spend the summer.

The most spectacular March migrant among birds of the open country is the sandhill crane. There are only a few places around Chicago where cranes are likely to touch down. Mostly, we see them passing overhead. They are easy to identify: big, gray birds that fly with their long necks outstretched and their long legs trailing behind. They move their wings in a distinctive way too, following each powerful downstroke with a sudden, flicking upbeat.

They announce their passage with their bugling calls, cries that can be heard for a mile or more. Cranes of all kinds have long, convoluted tracheae whose coils are held within the animals' breastbones. The trachea of a sandhill crane can be four feet long, almost as long as the tubing on a trumpet. You can usually hear a passing flock long before you can see it.

There are six distinct populations of sandhill cranes. Three--those in Cuba, Florida, and Mississippi--are sedentary. The other three are migratory. The birds we see here are greater sandhill cranes. They nest around the upper Great Lakes and winter in Florida. For the past several years, small numbers of these birds have been staying through the summer around Chain O' Lakes State Park west of Antioch, providing Illinois with its first nesting population in many decades.

Whooping cranes used to nest around here too. They were birds of wet prairies and prairie marshes, and Illinois was at the eastern end of a breeding range that extended northwest to North Dakota and the prairie provinces of Canada. Whooping cranes are very wary birds that cannot tolerate close human contact. They had vanished from this entire breeding range by the 1890s.

In the 1930s they became the first of the famous endangered species. By then the population had been reduced to about 15 birds that spent every winter on the Gulf Coast of Texas. The protection effort began in 1937 with the designation of their winter home as the Aransas National Wildlife Refuge. Their nesting ground, near the Arctic Circle in Canada's Wood Buffalo National Park, was not discovered until 1954. It took ten years of intensive aerial searching to discover it.

With the total population reduced to a single flock, the species could have been rendered extinct by one bad hurricane or one disease outbreak. In hopes of reducing the birds' vulnerability, the U.S. Fish and Wildlife Service decided to establish a captive flock. They had learned that whooping cranes usually lay two eggs. The female begins incubating the first egg as soon as it is laid, so it hatches some days before the second egg. The older sibling almost always kills the younger (ornithologists call this phenomenon "cainism"), so biologists concluded that they could remove one egg from each nest without lowering the flock's reproductive potential. Egg collecting began in 1967 and continued until 1974.

Despite the removal, the wild flock continued to grow. It now numbers 134 birds. The captive flock, at the Fish and Wildlife Service's Patuxent River (Maryland) research lab, now totals 40 birds.

Sandhill cranes became a part of this saga in 1975, when eggs from the captive flock were placed in sandhill nests at Grays Lake National Wildlife Refuge in Idaho. The sandhills successfully reared the young birds and led them on migration to their wintering grounds in New Mexico. However, the whoopers have not fared very well. Almost 300 eggs were placed, and nearly all of them hatched. But a combination of avian TB and a heavy concentration of electrical wires on the migration route has left only 14 birds still alive. The Grays Lake program is now suspended.

The Fish and Wildlife Service is planning to try to establish whoopers with the sedentary sandhill flock on the Kissimmee Prairie in central Florida. And they are considering another attempt at establishing a migratory flock with sandhills at Seney National Wildlife Refuge in Michigan's upper peninsula. Since the Seney sandhills pass through here in the spring and fall, we could someday see whooping cranes passing over Chicago.

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