Archives for posts with tag: natural history

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ROBIN EGGS: THE BLUER THE BETTER

Illustration and Text by Patterson Clark

(originally published 5/1/2012 in the Washington Post)

Not much point in looking around for a nearby nest when you find an American robin eggshell on the sidewalk.

Soon after a chick hatches, the female robin grabs the eggshell and flies off to drop it far from the nest. Leaving the baby behind for a few moments is worth the risk, since the bright white insides of the eggshell can attract predators.

But before the egg hatches, blue-green pigments on the outside surface of the egg might help with camouflage. Pigments might also strengthen the egg and help protect it from solar radiation.

A robin coats her eggs with the same turquoise-hued compound found in our bile and bruises, biliverdin, an important antioxidant. Female robins with higher concentrations of biliverdin in their tissue lay darker, more vividly colored eggs, which apparently sends a strong signal to males.

“Males seem to use egg color to gauge the quality of their mate and the eggs she lays, putting more effort into rearing babies when they are more likely to survive and prosper,” says Robert Montgomerie of Queen’s University in Canada.

With Philina English, Montgomerie determined that when eggs are more colorful, male robins will invest as much as twice the amount of energy helping feed nestlings.

SOURCES: Behavioral Ecology and Sociobiology; Bird Coloration: Function and Evolution; Stanford University

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END OF APRIL

by Phillis Levin

Under a cherry tree

I found a robin’s egg,

broken, but not shattered.
 
I had been thinking of you,

and was kneeling in the grass

among fallen blossoms
 
when I saw it: a blue scrap,

a delicate toy, as light

as confetti
 
It didn’t seem real,

but nature will do such things

from time to time.
 
I looked inside:

it was glistening, hollow,

a perfect shell
 
except for the missing crown,

which made it possible

to look inside.
 
What had been there

is gone now

and lives in my heart
 
where, periodically,

it opens up its wings,

tearing me apart.

 Illustration: “Opus No. 122” by Kazue Shima

“End of April” is found in Phillis Levin’s collection The Afterimage (Copper Beech Press, 1995), available at Amazon.com.

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When poet Phillis Levin found the robin’s eggshell under the cherry tree, she might have been interested to learn a bit more about its unique, vivid shade of blue. For this, we turned to an expert — Patterson Clark, who writes and illustrates the Urban Jungle column for the Washington Post.

Image

ROBIN EGGS: THE BLUER THE BETTER

Illustration and Text by Patterson Clark

(originally published 5/1/2012 in the Washington Post)

Not much point in looking around for a nearby nest when you find an American robin eggshell on the sidewalk.

Soon after a chick hatches, the female robin grabs the eggshell and flies off to drop it far from the nest. Leaving the baby behind for a few moments is worth the risk, since the bright white insides of the eggshell can attract predators.

But before the egg hatches, blue-green pigments on the outside surface of the egg might help with camouflage. Pigments might also strengthen the egg and help protect it from solar radiation.

A robin coats her eggs with the same turquoise-hued compound found in our bile and bruises, biliverdin, an important antioxidant. Female robins with higher concentrations of biliverdin in their tissue lay darker, more vividly colored eggs, which apparently sends a strong signal to males.

“Males seem to use egg color to gauge the quality of their mate and the eggs she lays, putting more effort into rearing babies when they are more likely to survive and prosper,” says Robert Montgomerie of Queen’s University in Canada.

With Philina English, Montgomerie determined that when eggs are more colorful, male robins will invest as much as twice the amount of energy helping feed nestlings.

SOURCES: Behavioral Ecology and Sociobiology; Bird Coloration: Function and Evolution; Stanford University