A European songbird that usually dines on insects and seeds has added an unusual item to its menu: hibernating common pipistrelle bats, BBC News reports.
Scientists writing in the journal Biology Letters, said that during two winters studying a cave in Hungary, they documented great tit songbirds “systematically hunting bats by sight and sound as they hibernated through the cold months,” said BBC reporter Richard Black. This is the first proof of songbirds actually hunting bats.
Researcher Bjorn Siemers of the Max-Planck-Institute for Ornithology in Seewiesen, Germany, told the BBC that the birds preferred other food when they could get it and bat-hunting probably is very rare (although bats are often hunted by hawks, owls and other raptors, and other birds are reported to eat bats on occasion).
“It doesn’t look like this is an overwhelming thing that threatens the bat population,” Siemers said. “So the question to ask is ‘how did they invent it?,’ and so far we can only speculate: it could be a kind of cultural learning,” he told BBC News.
Black said that other scientists previously have reported at least one European bat being eaten by a great tit and other bats that might have been killed or injured by the birds, but no conclusive evidence that the birds were actually hunting bats.
Working in northeastern Hungary, the researchers recorded 16 cases of great tits “hunting, killing and eating hibernating bats in the cave,” BBC said. The birds would fly into the cave, land and disappear into crevices used by bats, then either eat the bats in the crevice or carry them away.
Common pipistrelles are about one-fourth the size of a great tit, and when disturbed, the bats vocalize in a range that is audible for both humans and great tits. The researchers told BBC News that the birds may be listening for the bat sounds. When recorded bat calls were played back, Black said, “the birds responded with interest about 80 percent of the time.”
He added that scientists believe the birds can only hunt when they can actually see their prey, which is often impossible in pitch-dark hibernation caves. But a great deal of sunlight filters into this wide-mouthed cave in Hungary. That, the researchers conclude, suggests that bat hunting is rarely seen among these birds.
The scientists also provided other food items for the birds, finding that they mostly left the bats untouched when such things as sunflower seeds and bits of bacon were available. This, Siemers told the BBC, indicates that bats are a food of last resort in a harsh winter.