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.
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.
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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Update: June 2012