You may not have noticed it lurking behind the snowbanks, but spring is definitely creeping in. The birds are sure it is coming, even if you and I still have our doubts. The usual early-spring migrants–redwings, grackles, killdeer, robins–are flowing through in substantial numbers. Fox sparrows, the largest species of sparrow in North America, first showed up a couple of weeks ago, and of course song sparrows are already common.
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A flock of about a thousand sandhill cranes passed over the southern suburbs. They were headed northwest, probably toward their breeding grounds in central Wisconsin. The local resurgence of this species is one of the few pieces of good news about birds we have heard in these generally worsening times. After years of absence as a nesting species in Illinois, the cranes have become regular breeders at Chain o’ Lakes State Park. The large numbers we have been seeing passing through the Chicago area also suggest that the species is doing well on its long-established nesting sites in Wisconsin and upper Michigan.
Spring migration is a long and complex phenomenon. Birders have been watching it for generations now, so the patterns are quite familiar. We know what to expect and when to expect it.
In flight, mergansers look streamlined and sleek, without the dumpy build of other ducks. This profile is related to their way of life. They are the only ducks that catch fish. Other ducks are either vegetarians or eat animal food but go after small crustaceans, insect larvae, and other slow-moving stuff. You have to be quick and maneuverable to catch a fish. Mergansers look more like miniature loons than ducks.
Ducks are notoriously loose in their sexual habits. Hybrids between various species are quite common. Drakes of one species will court females of another species, and the females often respond. And the shocking irregularities don’t end there. Some ducks lay their eggs in the nests of other species. Redheads do this fairly often. They also build their own nests, but they tend to be rather casually attached to them. And they abandon their young at an earlier age than most ducks.
Migration reaches its peak in May–at this latitude about mid-May. There are more species and more individual birds to be seen then than at any other time of the year. The insect-eating songbirds–warblers, vireos, tanagers, flycatchers, swallows–are the most numerous.
