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Desert Diary
Birds/Speckled Eggs


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We've all seen pictures of bird eggs with splotches of color, usually brownish or reddish. For generations, the explanation has been that these act as camouflage against egg predators, helping to break up the oval outline and allowing the eggs to blend in better with the background of nesting material. And true, this may be one reason for the spots.

Scientists, though, are suggesting that there may be an additional reason. Researchers in the United Kingdom found that eggs of the Great Tit, white with red speckles, didn't have the pigmented spots scattered at random. Instead, they appeared at places where the eggshell was thinner; what's more, the thinner the shell at any one place, the heavier the pigment deposit. Also, the number of spots varied geographically, with regions having high levels of calcium tending to produce heavier shells—and fewer spots. The authors conclude that the pigments, known as protoporphyrins, reduced friction between the calcite crystals making up the shell, reducing brittleness and thus the likelihood of breakage. Too bad Humpty Dumpty didn't know about this!
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Listen to the Audio (mp3 format) as recorded by KTEP, Public Radio for the Southwest.


Contributor: Arthur H. Harris, Laboratory for Environmental Biology, Centennial Museum, University of Texas at El Paso.

Desert Diary is a joint production of the Centennial Museum and KTEP National Public Radio at the University of Texas at El Paso.