Forest Preserve District of Cook County, Illinois
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Bird's Eggs - Their Size, Shape and Color
Nature Bulletin No. 455-A   April 29, 1972
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation

BIRD'S EGGS THEIR SIZE, SHAPE AND COLOR


There is usually a time, especially in his youth, when a man seems to have the instinct and habits of a pack rat or a crow. A boy is liable to collect anything from "lucky" pebbles or marbles to picture cards, stamps, cigar box lids or butterflies. There was a time, 50 years ago and more, when many boys and men, too -- collected birds' eggs. In search of nests they roamed the woods thickets, meadows and swamps.

Of course, we lads acquired a fund of nature lore. It took sharp eyes, patience and knowledge of their habits to discover a meadowlark's nest hidden beneath a clump of grass, or the tiny lichen-covered nest of a hummingbird. But many boys and men took every egg from a nest and those were sad days for the birds. There was brisk trading of eggs between collectors, not only locally but throughout the country, and this hobby was so popular that there were several magazines devoted to it. Fortunately, now and for many years there have been stringent federal and state laws forbidding such practices.

Bird's eggs are extremely variable in every respect. The elephant birds of Madagascar, now extinct, laid eggs about 14 inches long with a capacity of about 2 gallons. In contrast, a hummingbird's egg looks like a small bean. Domestic chickens, when pullets, often lay very small eggs at first and the last eggs laid by old hens are apt to be unusually small. There are eggs with shells so thin and fragile that they are almost transparent but the sculptured porcelain shell of an ostrich egg, about 6 inches long, almost as much in diameter and weighing nearly 3 pounds, has to be opened with a hammer and chisel.

The eggs of birds vary in color from pure white to almost black. Those of the tinamous, South American game birds, have solid metallic colors and a finish like that of a new automobile. Most birds that nest in dark holes, like the kingfisher and the woodpeckers, lay plain white eggs; whereas those of the kill deer, whip-poor-will, plovers and terns, laid in exposed places with no protecting nest, are colored like the soil or gravel and are very difficult to find. The majority of birds that build protective nests lay eggs having a ground color of some delicate tint with spots, streaks or scrawls of darker pigment such as purple, brown or black and, often, this forms a kind of wreathe around the larger end. Robins and bluebirds have blue eggs but those of some other thrushes are spotted with darker color.

Birds' eggs are not even uniform in shape. Most of the 8600 or more species lay eggs shaped about like our familiar "hen fruit" but those of the owls and the Old World bee-eaters are nearly round, and many birds have eggs much longer than they are wide. The auk or murre nests on bare rock ledges of sea cliffs and lays an extremely pointed egg which, if accidentally kicked, will roll a circle instead of over the edge. Plovers and sandpipers also lay pointed eggs. Arranged on the ground, with the points inward, they occupy less space and, although rather large, can be more easily covered by the brooding mother.

Some of the penguins, albatrosses and other sea birds that nest in accessible places lay only one egg. The California Condor, nearly extinct, lay but one and that was true of the extinct passenger pigeon and the great auk. Wild ducks and game birds such as quail and pheasants, which have numerous enemies, lay 15 or more in a clutch. Most songbirds lay from 3 to 5, although hole-nesters like chickadees may lay 8 or more; tropical species seem to lay fewer eggs than their northern relatives; hawks and owls lay more eggs when their prey is plentiful; but nobody ever saw a square one.


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