By Karen E. Worley MANAGING EDITOR
Photos by Ken Bohn SDZG PHOTOGRAPHER
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hat’s in an egg? In addition to a growing chick, quite a lot. An egg is one of nature’s marvels, a well-constructed container that not only protects a developing embryo but also provides it with almost everything it needs, all in one perfect package. While most of us are familiar with the white and sometimes brown chicken eggs at the grocery store, the variation in these avian vessels covers a wide spectrum of sizes, shapes, and colors, depending on the species. Plus, the structure of an egg is a remarkable puzzle in itself. Ready for a little “eggs-ploration?”
Sizing It Up
It makes sense that a big bird lays a big egg, and the ostrich lays the biggest: seven inches long, five inches wide, and weighing three pounds. At the other end of the scale are hummingbird eggs, which
can be about a half-inch long and a quarter-inch wide, weighing less than a pea. And there are eggs of just about every size in between. Some bird species lay clutches of several eggs, while others lay only one or two. Species that have more developed, precocial chicks tend to produce larger eggs than those with less developed, altricial chicks. That’s because precocial chicks typically spend more time incubating inside the egg before they hatch, and they need more yolk and protection to support them. But there is one unusual bird that stands out in the egg department: New Zealand’s kiwi. The female kiwi manages an incredible feat—she produces one egg that is almost one-third the size of her entire body, taking up a huge amount of internal space until it is laid. Apparently, nature decided that after all that, she needed some help, since the male kiwi takes over incubation duty.
Same contents, different size: Whether it’s a seven-inch ostrich egg, a two-inch chicken egg, or a quarter-inch hummingbird egg, each one contains all the structures and nutrients needed to make a chick.
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