Blue-footed boobies protect their eggs by dirtying them
Numerous birds have been known to camouflage their eggs to protect them from predators, but one species appears to have a rather unique way of going about it.
While most are known to use pigments, a recently published study has found that blue-footed boobies color their eggs with nearby dirt.
Biologists studying the birds on the Pacific island of Isla Isabel had noticed the browning before but thought it was a result of the eggs incubating on the ground without a nest.
But then a team assessed the birds' behavior around their eggs in 2012 and analyzed prior data related to more than 3,600 eggs between 1981 and 2011.
During this latter 20-year period, they determined that the casualty rate in the first five days, when the eggs are their whitest, was nearly half, or 47 percent.
But as the eggs became increasingly camouflaged with dirt over the initial 16 days, there was corresponding boost in the chance of survival. They also proved to be less vulnerable throughout the remainder of the incubation period which typically lasts around 41 days.
The flexibility of the egg staining method is believed to afford the birds more options when choosing incubation sites.
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