Large and small, plain and colored, splotched and dotted, eggs from the Harvard Museum of Comparative Zoology’s vast collection are on display at the Harvard Museum of Natural History in a new exhibition of eggs and nests.

The nests, like the eggs, come in all shapes and sizes. Unlike eggs, which have the same basic plan, nests vary greatly in complexity, from the simple dirt mounds of reptiles to the elaborate creations of Africa’s weaver birds to no nests at all.

Scott Edwards, Alexander Agassiz Professor of Zoology and curator of ornithology at the Museum of Comparative Zoology, said the new exhibit uses eggs and nests as an accessible way to educate the public about birds. Because for birds, Edwards said, much of their lives revolves around building nests and filling them with eggs.

“It’s springtime. Eggs and nests are one of the more accessible routes into bird biology,” Edwards said.

The exhibit, which opened to the public May 18, runs through March 2008.

In an opening lecture on Thursday (May 17), Edwards gave the audience at the Geological Lecture Hall a global tour of eggs, nests, and the creatures that build them.

Edwards traced mammals, birds, and reptiles back to a single ancestor. While mammals went on to develop a largely egg-free way of reproducing, Edwards pointed out that some mammals, such as the platypus, continue to give birth to young in eggs.

Reptilian egg-laying habits evolved over time, through what Edwards referred to as “nonavian dinosaurs” to birds.

While reptiles lay leathery eggs in earthen nests, birds have developed a harder shell for their young and lay their eggs in nests that span the spectrum of form and structure. Emperor penguins use no nest at all, incubating their young on the feet of male birds, protected from the bitter Antarctic cold by a flap of skin while the male fasts and the female goes in search of food.

Other birds create a variety of nests, from the intricate interlacings of weaver birds to the astounding hardened-saliva constructions of swifts, whose nests are collected for bird’s nest soup.

Eggs come in an enormous variety, from the 3.3-pound ostrich egg, to the 0.03-ounce egg of the hummingbird. Extinct now is the champion of all, the egg of the elephant bird, as much as seven times bigger than the ostrich egg.

Birds have also developed different strategies in egg size. A larger egg, favored by ground nesting birds, means more nourishment for the young. It requires a longer incubation time, but develops young that can begin to move and eat right after hatching. Other birds have a different strategy, laying smaller eggs yielding young that are helpless and dependent on parental care.

“Everything in a bird’s life revolves around eggs and nests and reproduction,” Edwards said.

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