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Why robin eggs are blue

Mystery of blue-green bird eggs solved: Researchers show that egg color protects the embryo from harmful sunlight

Date:
May 27, 2016
Source:
University of Chicago Press Journals
Summary:
Scientists are testing the hypothesis that blue eggshells (unlike dark colors) both shield the interior from UV radiation and prevent the egg from heating up.
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People have always wondered why many birds lay bright blue eggs.

David Lahti of the City University of New York and Dan Ardia of Franklin & Marshall College tested the hypothesis that pigmentation might help an egg strike a balance between two opposing and potentially damaging effects of the sun: light transmission into light-colored eggs, and heating up of dark-colored eggs.

As predicted, more intensely blue eggshells shielded the interior from light, including dangerous UV radiation--but more intense color also caused eggs to absorb more light and heat up, which can be even more dangerous in brighter environments. These two patterns--termed by the authors "pigment as parasol" and the "dark car effect"--combined with a knowledge of the nesting behavior and habitats of birds, can lead to predictions as to why the eggs of some birds vary across species from blue to white.

Darker eggs are predicted in moderate light to shield the embryo, but in brighter nests the dangers of egg heating predict lighter colored eggs. Whereas camouflage from predators is still probably the single most important factor governing the evolution of dull and mottled egg colors, for the brighter colors the biophysical evidence points to the sun.


Story Source:

Materials provided by University of Chicago Press Journals. Original written by David C. Lahti and Daniel R. Ardia. Note: Content may be edited for style and length.


Journal Reference:

  1. David C. Lahti, Daniel R. Ardia. Shedding Light on Bird Egg Color: Pigment as Parasol and the Dark Car Effect. The American Naturalist, 2016; 187 (5): 547 DOI: 10.1086/685780

Cite This Page:

University of Chicago Press Journals. "Why robin eggs are blue: Mystery of blue-green bird eggs solved: Researchers show that egg color protects the embryo from harmful sunlight." ScienceDaily. ScienceDaily, 27 May 2016. <www.sciencedaily.com/releases/2016/05/160527190410.htm>.
University of Chicago Press Journals. (2016, May 27). Why robin eggs are blue: Mystery of blue-green bird eggs solved: Researchers show that egg color protects the embryo from harmful sunlight. ScienceDaily. Retrieved May 27, 2017 from www.sciencedaily.com/releases/2016/05/160527190410.htm
University of Chicago Press Journals. "Why robin eggs are blue: Mystery of blue-green bird eggs solved: Researchers show that egg color protects the embryo from harmful sunlight." ScienceDaily. www.sciencedaily.com/releases/2016/05/160527190410.htm (accessed May 27, 2017).

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