Many species of birds use shed snake skin when building nests, but this behavior is poorly understood. In a new study, Cornell University ornithologists used comparative and experimental approaches to suggest that the evolution of this behavior is mediated by nest morphology and predator community. They used a series of experiments and comparisons to test four hypotheses (nest predation, nest microbiota, nest ectoparasites, and social signaling) that snake skin confers fitness effects, and the predation hypothesis found support for.
Great Crested Flycatcher (Myialchus crinitus) are famous for using snake skin to construct their nests. Image credit: Barbara Taylor/Macaulay Library.
“What do snakes eat? They eat a lot of rats and small mammals,” said Dr. Vanya Lower, lead author of the study.
“Given the evolutionary history of harmful interactions between small-bodied predators that are commonly eaten by snakes, these predators should become fearful of snake skin in their nests.”
“It may change the decision-making process for whether or not to nest.”
“Birdwatchers have been recording the use of snakeskin in nests for centuries, and have speculated that snakeskin occurs more frequently in hollow nests, but no one has tested this theory. There was no one there.”
“We were trying to understand why birds spend so much time and effort finding this strange substance.”
First, Dr. Lower and his colleagues looked at the literature and found that 78 species in 22 families have been reported to use shed snake skin for nest building.
All but one of these species are passerines, and in a comparative analysis, the researchers found that this behavior was disproportionately observed in cavity-nesting species.
Next, they examined a subsample of North American species, all of which are reported to use snake skin for nest construction, and found that between cavity-nesting species and open-cup nesting species, snake skin We investigated whether the proportion of nests with
The analysis suggested that the proportion of nests with snake skin was approximately 6.5 times higher in cavity nests than in open cup nest species.
“The proportion of nests that had snake skin in the nest description was about 6.5 times higher in cavity nests than in open cup nests,” Dr. Lower said.
“This was really, really cool and suggested to us that these two completely independent data series were telling very similar stories.”
To test the benefits that cavity-nesting birds derive from snake skin, scientists investigated how snake skin reduces nest predation, reduces harmful nest ectoparasites, and benefits birds. We investigated whether they can alter the microbial community or serve as a signal of parental quality. Parents make more efforts to raise their children.
Of these ideas, the results supported the nest predation hypothesis, but only in cavity nests.
For the experiment, the authors placed two quail eggs in more than 60 nest boxes and more than 80 inactive robin nests set up around Ithaca’s Monkey Run Natural Area. Cavity nests and open cup nests were simulated.
Some nests received snake skins collected from local snake breeders, while others did not.
Every three days for two weeks, the team used a ladder to climb through the monkey run to the nest and check for eggs.
Trail cameras revealed that while small mammal and bird nest predators visit open cup nests, only small mammals, namely flying squirrels, visit nest boxes.
“If you were in a hive like that and you had snake skin, you would have a much better chance of surviving those 14 days,” Dr. Lower said.
“The benefits of the material are most strongly expressed in hollow nests.”
team’s result appear in american naturalist.
_____
Vanya G. Lower others. Evolution of the use of snake skin in bird nests. american naturalistpublished online on December 17, 2024. doi: 10.1086/733208
This article is a version of a press release provided by Cornell University.
Source: www.sci.news
