Which came first? The bird or the egg?
That long-running philosophical mystery hasn’t been solved, but it does clearly focus on one thing that makes birds unique: All birds lay eggs in order to reproduce; no birds give live birth to their young. On the other hand, all but a handful of mammals do give live birth to their young. These exceptions are the duck-billed platypus and the echidna (a species of spiny anteater) that are definitely odd-ball mammals in that they lay eggs.
Still, it’s birds that are such dedicated egg layers. From the largest to the smallest, all birds start out life by hatching from eggs.
Photo by U.S. Fish & Wildlife • Eggs of a yellow warbler snug in the nest.
The world’s largest bird, the ostrich, produces the largest egg of all birds. Each egg weighs a little more than three pounds. An ostrich hen can…
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