In 1889, naturalist Alan Octavian Hume wrote that he was perplexed by the eerie decorations he observed in many bird nests: strips of dried snakeskin.
“Are birds superstitious?” Do they believe in amulets? He writes in “Nests and Eggs of Indian Birds.” If not, why did so many birds use scraps of snakeskin to decorate their nests? We hypothesized that.
A new study suggests they were on to something: After analyzing centuries of bird nest records and observing more than 140 nests with and without snakeskin, the study Last month, researchers reported in The American Naturalist that the presence of snakeskin plays a major role in some species' nests. Reduced risk of predators stealing eggs.
All reptiles shed patches of dead skin as they grow, but snakes shed skin all over their bodies in one large clump. But finding snakeskin in the wild can be difficult, said Vanya Lower, a curator at Cornell University's Museum of Vertebrate Zoology and author of the study. It is even more remarkable that so many birds use snakeskin in their nests because of its rarity.
“How on earth do they find it? And why do they spend all that time trying to bring it back to the nest?” Dr. Lower said.
Dr. Lower pored over digitized historical records of bird nesting behavior, including handwritten nest observations from more than 100 years ago. He and his colleagues found that cavity-nesting birds (birds that nest in holes in structures such as trees or cliffs) are more likely to use snake skin for nests than species that make more “classic” cup-shaped nests. We determined that they were 6.5 times more likely to be incorporated into
Based on this information, Dr. Lower devised a series of experiments “to try to understand the benefits of shed snake skin.” He investigated microorganisms and large parasites in nests with and without snakeskin to see if the skin repelled creatures such as fleas and ticks or reduced harmful microorganisms in the nest. . There didn't seem to be any correlation. “Another idea we considered was the idea of nest predation,” Dr. Lower said.
In a wooded area called Monkey Run near the Cornell campus in Ithaca, New York, Dr. Lower placed quail eggs into 65 hollow-nest-like nest boxes and 80 empty robin nests (open-cup nests). Ta. He added snake skin to half of the nest and spent the next few weeks checking the nest using a ladder. “My wife gave me the nickname Rudderman,” he said.
During his stint as Ladder Man, Dr. Lower made a surprising discovery. Snake skin did not seem to make a big difference in the safety of eggs in open cup nests, but scaly debris made a big difference inside nest boxes.
“Cavity nests with snakeskin were much more likely to survive the 14-day incubation period than those without snakeskin,” he said. In particular, snakeskin seemed to deter small mammals like mice, which are known to eat eggs.
This finding suggested further questions. “What's scary about snakeskin?” Is it the smell of snakeskin? Is it the sight of snakeskin for this small mammal? ” Dr. Lower said.
Australian National University ecologist Ross Crates, who was not involved in the study, said other studies have shown that some birds hiss to scare away predators from their nests. “Pretending that there is a snake in the nest in some way is beneficial to small birds that nest in holes. These birds may actually use their nests to prey on larger, primarily mammalian predators.” “They have a lower ability to physically protect themselves from this,” Dr. Crates suggested.
Dr Lower said nests can be difficult to observe and study and have traditionally been overlooked in scientific research. Digitized datasets like the one he and his colleagues used are helping researchers make discoveries. “We're just now starting to really look at some of the unique substances found in bird nests,” he says.