Monday, April 6, 2009

Why do robins lay blue eggs?*

These beauties live in the tree beside my carport. I'm a little concerned about them--it's supposed to get cold tonight.
*Let me know if you have an answer to this question. I tried Googling it but got bored.

10 comments:

Anonymous said...

Don't worry, the mother robin will keep them warm.

Grandma

Anonymous said...

This is an answer I found online by a Cornell ornithologist.

Why are robin's eggs blue?

Question
More than 30 years ago, famous bird biologist David Lack wondered the same thing. He noticed that birds nesting on the ground often lay brown or gray eggs that blend in with the surroundings. And birds that lay highly visible white eggs often conceal their nests in a hole. He suggested that the blue eggs of many songbirds might blend in at the bottom of a dark nest that is screened by leaves from above. This could help hide the eggs from predators such as squirrels, ravens, and jays. But, he admitted, blue eggs were the "biggest puzzle."

Franz G�tmark tried to solve the puzzle by painting quail eggs white, blue, or spotted, then putting them in artificial nests in trees. Predators took all three types equally. So although, in theory, blue eggs in nests might be hard to find, scientists haven't yet come up with the evidence.

And that's just one of the mysteries when it comes to the color of eggs. Why are an emu's eggs dark green like an avocado? Why are a Chilean tinamou's eggs purplish? I don't know.

Most birds have pigment glands that deposit colors on the egg as it passes through the oviduct. Usually each bird species has a characteristic egg color.

But in some species, such as the common murre, different females lay eggs with different colors—for example, bright pinkish, creamy or pale blue. Additionally, the eggs can have black, red, or yellowish-brown blotches or squiggles. A murre lays her eggs on a ledge near the eggs of other females. Distinctive eggs may help her recognize which ones are hers. Experiments show that a murre will only accept a new egg if it resembles her own.

OK, but why do the eggs laid by the same American crow look so different from one another—some heavily spotted, others nearly plain? Maybe some day you can help us find out.

Anonymous said...

That was from Aunt T

Leah said...

I hope they're okay! The mom might get cold too. Has she come back?

The Bakers said...

Does it make me sound shallow if I say those eggs are so pretty? I am concerned about the baby birds as well, of course.

Bowlby said...

Not shallow, Julia. My first thought was, "Do you think the mother bird would notice if I took one of the eggs to the Benjamin Moore store to have paint matched?"

{Kidding, kidding!}

Leah said...

You could wait until they're hatched and then take in the shell.

Anonymous said...

I'm surprised you were able to get close enough for that shot - surprised the mother bird did not dive bomb you. Robins are know for that behavior. Ask Aunt T.

Grandma

Anonymous said...

Is Robin's egg blue in the crayola 64 crayon box? I love that Everyone knows what color that is. Mary (Robin's sister)

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