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.
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.
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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.
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.
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.
