When a bird decorates its nest with snake skin, it serves a purpose beyond mere aesthetics. Researchers from Cornell University have discovered that for certain birds, this choice helps to deter predators.
When a bird decorates its nest with snake skin, it serves a purpose beyond mere aesthetics. Researchers from Cornell University have discovered that for certain birds, this choice helps to deter predators.
Scientists have analyzed both new and historical data, revealing that birds that build nests in cavities — which have small openings — are more inclined to incorporate shed snake skins in their nests compared to those that create open-cup nests. This behavior appears to help protect their eggs from potential predators.
“What do snakes eat? They primarily consume mice and small mammals,” explained Vanya Rohwer, the lead author and senior researcher of the study published in The American Naturalist.
“We hypothesize that the evolutionary history of dangerous encounters between smaller bird-eating predators and snakes leads these predators to be wary of finding snake skin in a nest,” Rohwer noted. “This could influence their decision on whether or not to approach a nest.”
Birdwatchers have observed the use of snake skins in nests for hundreds of years and have theorized that this occurrence is more common in cavity nests. However, this theory had not been put to the test, according to Rohwer.
To investigate the potential advantages of snake skin for birds, researchers considered whether it could lessen predation on nests, reduce harmful parasites, alter microbial communities in ways that are beneficial for birds, or act as a signal of parental quality, leading to increased parental investment in raising their young. Their findings supported the idea that snake skin helps reduce nest predation, but only in cavity nests.
For their experiment, researchers placed two quail eggs in over 60 nest boxes and 80 abandoned nests of American robins around the Monkey Run Natural Area in Ithaca to mimic cavity and open-cup nests. Some of the nests contained snake skins obtained from a local snake breeder, while others did not.
Every three days over a two-week period, researchers would climb up to the nests using a ladder to monitor the eggs.
Footage from trail cameras showed that small mammals and birds of prey frequented the open-cup nests, while only small mammals — particularly flying squirrels — visited the nest boxes.
“If you were in one of those nest boxes with snake skin, your chances of surviving that 14-day period were significantly higher,” Rohwer stated. “The advantages of using this material are particularly pronounced in cavity nests.”
