God and evolution: weaverbirds (Evolution)

by David Turell , Wednesday, January 15, 2025, 19:25 (58 days ago) @ David Turell

A new study with snake skins:

https://phys.org/news/2025-01-cavity-birds-cleverly-snake-skin.html

"When a bird drapes its nest with snake skin, it isn't just making an interesting home décor choice. For some birds, it keeps predators at bay.

"Researchers combined new and historical data to show birds that nest in cavities—covered nests with small openings—are more likely to use shed snake skins in their construction than birds that build open-cup nests, and this practice helps deter predators from eating the eggs.

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"Birdwatchers have documented the use of snake skins in nests for centuries and speculated that it occurs more in cavity nests, but no one had tested this theory, said Rohwer, who is also a curator at the Cornell University Museum of Vertebrates, housed at the Lab of Ornithology.

"'We were trying to address why birds are investing all this time and effort in finding this bizarre material," he said.

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"'The proportion of nests that had snake skin in the nest description was about 6.5 times higher in cavity nests compared to open cup nesters," Rohwer said. "So that was really, really neat, and that suggested to us that we have these two totally independent lines of data that are telling a very similar story."

"To test what benefit cavity-nesting birds might be getting out of the snake skin, the researchers explored if snake skin could reduce nest predation, reduce harmful nest ectoparasites, change microbial communities in ways that benefit birds or function as a signal of parental quality and increase the effort parents make in raising their young. Of these ideas, their results supported the nest predation hypothesis, but only in cavity nests.

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"'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 said. "The benefits of the material are most strongly expressed in cavity nests.'"

Comment: this covers weaverbirds as part of a generalized 'cavity nest' birds group, and adds a interesting fact. Obviously a learned behavior.