What came first, the chicken or the egg?

Eggs were around long before there were chickens. In addition to birds, mollusks, fish, insects, frogs, reptiles, and even some mammals lay eggs. These mammals are known as monotremes. The closest living relatives of birds include crocodiles, lizards, snakes, and turtles, all of which lay eggs with soft shells.  Birds have evolved a hard-shelled egg to protect the egg from breaking or drying out as the chick develops.

Laying eggs instead of giving birth to live young has several advantages for birds.  Eggs are heavy and, in most species, the female lays more than one egg. These would be too heavy for the female bird to carry around inside her body as they developed if she were to give birth to live young. Also, laying eggs allows the male bird to help with caring for the eggs.

Large, dark colored emu egg in a pale blue box

This Emu (Dromaius novaehollandiae) egg from DMNH’s scientific collection
was collected April 20, 1902 in Port-Darwin, Northern Territory, Australia.

Did you know?

  • Most birds lay their eggs early in the morning
  • The group of eggs a female lays in her nest is called a clutch
  • In many species, the clutch is just one egg, but in some it may be more than 20 eggs.
  • In many species, the female can lay one egg each day, while in others it may take up to eight days to produce an egg.
  • The number of eggs laid can be affected by how much food is available to the female.

Great White Heron (Ardea herodias occidentalis) eggs collected March 30, 1925
by Edward Jay Court and Louis Weber, now in the scientific collection.

Our Collection

The Delaware Museum of Natural History has 36,000 clutches of eggs, the second largest collection of bird eggs in North America. Many of the eggs in our collection were collected before 1900. Collecting bird eggs was a popular hobby in the late 1800s. It is now illegal to collect wild bird eggs in the U.S., but eggs collected decades ago provide detailed data for scientists. Scientists from all over the world use our collections in their research.

Tinamou eggs, such as these from the DMNH scientific collection, are naturally glossy.