A new study, based in the Monkey Run Natural Area just outside Ithaca city in New York State, has found that when birds line their nests with snake skin, it's not just for decoration – it’s a clever way to keep predators away, too.
Birds nesting in enclosed spaces, such as tree cavities, are more likely to use shed snake skins than those building open-cup nests, say researchers from Cornell University. This tactic helps protect their eggs from predators.
“What do snakes eat? They eat a lot of mice and small mammals,” explains lead researcher Vanya Rohwer. “We think that an evolutionary history of harmful interactions between small-bodied predators of birds that are often eaten by snakes should make these predators afraid of snake skin inside of a nest.”
“It might change their decision-making process of whether or not they’re going to go into a nest.”
Birdwatchers have long noticed this behaviour, but no one had tested whether it actually deters predators – until now, say the researchers.
Nest test
To test this predator-deterrent hypothesis, the scientists set up an experiment in the 550-acre Monkey Run Natural Area, a protected woodland corridor surrounding Fall Creek just east of Ithaca. They placed two quail eggs inside more than 60 nest boxes and 80 inactive American robin nests to simulate cavity and open-cup nests. Some nests contained snake skins, while others didn’t.
Over a two-week period, researchers regularly climbed up to the nests to check on the eggs. Motion-activated cameras showed that open nests attracted both birds and small mammals, while enclosed nests were mostly visited by flying squirrels.
“If you were in one of those nest boxes and you had snake skin, you had a much higher chance of surviving that 14-day period,” Rohwer says. “The benefits of the material are most strongly expressed in cavity nests,” he concludes.
Find out more about the study: The evolution of using shed snake skin in bird nests
Main image: foggy forest in New York State (not study site)/Getty
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