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Thursday, May 25, 2006

Eggs-actly right

Here is an eggshell I found on the ground today, not far from our Eastern Phoebe's nest. It is possible that this is the eggshell from a newly hatched Phoebe chick (they have white eggs) and the parents removed the shell from the nest. There is a chip out of one side and that
may be where the parent's bill carried it. It was lying on the dirt, hence the black flecks in the shell. I put it on a blue plate to photograph it.

You can tell by looking at it, that it came from a successfully hatched young and was not an egg gotten by a predator. Eggs that have come to harm, if there is anything left, are usually irregularly broken, smashed in, or are in pieces.

This eggshell is cracked evenly around the large end of the egg. When a baby bird is in the egg, just before it will emerge, it begins to "pip", or crack the egg. The chick has an "egg tooth" on its bill (lost soon after it is born), a specialized little tooth with which it begins to peck at the shell from inside in order to get out of the shell. It also has a hatching muscle on the back of its head that gives it the thrusting power to break through the egg. The chicks head is in the large end of the egg and gradually the chick turns in the egg and, using the egg tooth, cracks the egg evenly all around. Then the blunt end falls away and the baby bird emerges from the egg.

So this shell is evidence that this chick emerged exactly right.

Photo © Lillian Stokes, 2006

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