Penguins eat mollusks for harder eggshells

[United Press International]

SEATTLE, May 10 (UPI) -- Female penguins tend to eat a lot
of mollusk shells to help thicken their eggshells, thereby
protecting them from harm, said researchers in Seattle.
University of Washington scientists said a Magellanic
penguin mother must ensure her eggs come with extra-thick shells to
withstand being laid on hard surfaces and survive being kicked
during penguin fights.
During the period when eggs are laid, female penguins have
significantly more clam and mussel shells in their stomachs than do
males, according to the researchers.
The mollusk shells gradually leach calcium used to form
eggshells.
While the research centered on penguins, study author Dee
Boersma said the thick-shell pattern follows for some other birds as
well.
"The birds that lay eggs on rocks or those that tend to lay
them from great heights, like ostriches and rheas, also tend of have
thicker eggshells," she said.
The study is published in The Auk, a quarterly journal of
the American Ornithologists' Union.