How rude!

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Scientists are surprised to learn that some birds risk life and limb to pluck fur for their nests directly from live mammals.

The results of a recent study, cleverly titled "What the Pluck?" were published last month in the journal Ecology. In it, researcher Jeffery Brawn, a natural resources and environmental sciences professor at the University of Illinois Urbana-Champaign, cites numerous instances of hair thievery phenomenon, including his own video of a titmouse robbing a sleeping raccoon of tufts of its fur.

"The titmouse I saw was plucking hair from a live animal," Brawn said in a statement released by the university. "This was from a live raccoon with claws and teeth. And the raccoon didn't seem to mind because it didn't even wake up."

Prior to Brawn's observations, it was assumed that birds gather mammal hair that had been shed into the environment or from carcasses. The idea that industrious birds would go right to the source for their nest-building material is relatively novel.

Brawn and his colleagues named the strange behavior "kleptotrichy"—which roughly translates in Greek to "hair-stealing."

The researchers found only 11 mentions of kleptotrichy in scientific literature, with most involving the Paridae family (tits, chickadees, and titmice) of birds. On YouTube, however, they discovered a whole heap of evidence against the offending birds.   

They found a total of 99 incidents of kleptotrichy committed by birds, including 47 against humans, 45 against dogs, three cats, three raccoons, and even one porcupine. Sometimes the target animals were sleeping, and sometimes they were awake.

"We know, of course, that birds use a variety of materials to line their nests," Mark Hauber, the study's co-author and a professor of evolution, ecology, and behavior at the University of Illinois Urbana-Champaign, said in a statement. "But why are these birds risking their lives to approach these mammals?"

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The hair's role in the nest is still debated, although it's known to be great at insulating against cold. It might also repel nest and nestling parasites.

While more research is needed, Henry Pollock, the postdoctoral researcher who led the write-up, believes studies like this one highlight the hidden lives of animals.  

"Unexpected interactions such as these remind us that animals exhibit all types of interesting and often overlooked behaviors and highlight the importance of careful natural history observations to shed light on the intricacies of ecological communities," Pollock said.

Pretty cool, y'all!