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The storm that hit the day before Halloween marked the end of the soft autumn days that provide Chicago with its annual taste of perfect weather. The seasonal shift announced itself at my house about 3 AM, when the wind blew a large packing box into the fence under my bedroom window. I awoke expecting to see a truck bursting through the wall. The wind--twisting and whirling between apartment buildings--was actually roaring. The bedroom window had been open since May. Now it was time to close it.

In the morning there were tree limbs down in Berger Park, but the lake was paradoxically quiet. The northwesterly winds were blowing all the water toward the Michigan shore. Wires were down all over the region. My nephew in Des Plaines was without power for 27 hours. This kind of weather at this time of year means one thing to me: birds.

By late October the tiny songbirds are mostly safe in the tropics. This is the time when the big birds pass through, and in the wake of the storm the Chicago Audubon Society Rare Bird Alert (847-671-1522) was filled with spectacular reports. Like the 2,280 sandhill cranes one observer counted while looking through the windows of a north-side apartment about a mile from the lake.

Sandhill cranes are easy to identify and hard to miss. On the ground they stand four feet tall. In the air their wings may span seven feet. If you see some very big birds passing over, check out their legs and their necks. Long legs extending well beyond the tail and a neck held in an S-curve identify a heron or egret. A long neck extended out straight ahead of the body and stubby legs that don't reach the tip of the tail identify a goose. A long, straight neck and long legs identify a crane.

When the wind is blowing at something less than a roar, we usually hear sandhill cranes before we see them. Cranes have elongated trachea that enable them to make very loud noises. You can hear them literally a mile away. The trachea is coiled in loops along the sternum. In the whooping crane the uncoiled trachea would be longer than the bird.

If humans had trachea as long--proportionately--as those of cranes, normal breathing would not keep us alive. It would just push and pull stale air back and forth in the tracheal tube. For cranes, normal breathing means sucking in air like a weight lifter about to try a 400-pound clean-and-jerk.

The call of cranes is a high, clear cry rather like that of geese--although once you hear a crane you will never confuse it with a goose.

Sandhill cranes seem to have improved their circumstances in recent years. In the midwest their main breeding grounds are in upper Michigan and central Wisconsin, but lately they have returned to Illinois, with a few pairs nesting at Chain-o-Lakes State Park. They have long passed over Chicago on their way to their winter quarters in Florida, but 2,280 has to be among the all-time high counts for one day. On the same day an observer at Illinois Beach State Park north of Waukegan counted 1,500 birds.

The observer who recorded that amazing 2,280 cranes--birding is the only nature-study activity you can do through an apartment window--also saw 70 red-tailed hawks, an osprey, and a bald eagle, all swept in by the storm. (Very big birds with short necks and short legs are all raptors: hawks, eagles, vultures, or owls.)

Raptors like to take advantage of favorable winds too. Those 70 red-tailed hawks were topped by the 220 seen that same day at Illinois Beach State Park. The last bit of natural lakeshore in Illinois had seven other species of hunters as well, including 62 sharp-shinned hawks.

Gulls were among the hitchhikers on the storm. Franklin's gulls turned up at Montrose Harbor and at Gillson Park in Wilmette, with no less than 35 birds at Montrose. Franklin's is decidedly not a sea gull. It nests in the pothole lakes and marshes of the Great Plains. Only in winter does it appear over salt water, after a flight from the Dakotas and Saskatchewan to the Gulf of Mexico.

This bird was unknown to early ornithologists, since it does not occur in the east. The first specimens were migrants blown east on their fall flight to the gulf. We see them here every fall when the winds are right.

Many animals migrate. Salmon swim out to sea in the year of their birth and return to the rivers to spawn. Until late in the last century North American bison moved north and south with the seasons in search of good forage. Arctic caribou and African wildebeests still do the same. Monarch butterflies--like the children of Israel wandering in the desert--take generations to complete their migration from Mexico to southern Canada.

For sheer drama, the migrations of birds top all of these peregrinations. With hundreds of species and millions of individuals on the move, the migration sweeps across the midlatitudes. Some birds migrate short distances. Many of our robins will spend the winter in Kentucky or Arkansas. Some species--red-tailed hawks among them--are partial migrants: some birds go south, some stay home.

Cerulean warblers--birds weighing less than ten grams--fly from Illinois to the Andes each fall and return in the spring. The champion long-distance migrant is the arctic tern, which makes an annual flight from the arctic to the antarctic and back every year. It has been pointed out that arctic terns spend more of their lives in daylight than any other species on earth.

Here in the midlatitudes the grandeur of the weather adds even more drama to the trek. In spring and fall much of our weather is the product of massive collisions between air masses from north and south. The warm, moist southern air and the cold, dry northern air do not mix well. Instead, the air masses create fronts, frontiers hundreds of miles long. Winds swirl into the low-pressure areas along the front. The warm air from the south rides up over the colder, denser air from the north. As it rises, it cools and water precipitates from it.

For us earthbound creatures, the massive storms that form along fronts are mainly problems. They blow tree limbs onto our roofs, deprive us of electric power, and create floods. For migrating birds, the storms are opportunities. Once they get up into those winds, the birds can travel hundreds of miles with very little effort.

Of course there are problems with this sort of hitchhiking. Like a frog taking a ride in a powerboat, the birds have little control over where they go. The general direction may be good, but you can't expect pinpoint accuracy. And since the birds fly mainly at night, it is difficult for them to get visual clues as to their exact whereabouts. They just have to wait for daylight and then figure out where they are.

From a birder's point of view, this imprecision is excellent. Thanks to the winds, spring brings us southern species such as blue grosbeaks that have overflown their usual nesting grounds. And the storms of autumn carry in Franklin's gulls making a detour on a flight from North Dakota to the Gulf of Mexico.

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