Eggs are not all the same shape as the chicken eggs that we eat. Even the shape of the domestic chicken egg is different from that of its wild ancestor, the Red Junglefowl. Some birds eggs are more pointed, or pyriform and, at the other extreme, some are more rounded or spherical.

Many Factors Affect Egg Shape

  • Egg shape is determined by the internal structure of the hen. Her oviduct, distribution of internal organs and shape of her pelvic bones all affect egg shape. The Mallard’s egg at the top of this picture is subelliptical (not quite spherical). The Great Horned Owl’s egg is spherical and the Red-tailed Hawk’s egg, at the bottom, is elliptical.

Consequences of Shape

  • Aristotle once suggested that males came from more pointed eggs and females from more rounded eggs. This of course, is not true. The shape of an eggshell does affect its physical properties, however. The general spherical shape of an egg maximizes shell strength while also conserving shell materials. More rounded eggs further maximize the volume of the egg for theamount of eggshell as well as ensure heat conservation.

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