A wasp was caught on camera attacking and killing a baby bird

A wasp’s bites may be as bad as its sting. A paper wasp (Agelaia pallipes) has been caught on camera attacking and killing a baby bird in its nest, researchers report July 13 in Ethology.

The video shows the wasp landing on the 4-day-old lined seedeater’s head while its parents were away. The wasp repeatedly bit the nestling and tore at its flesh, leaving it bloodied and mortally wounded. Other young birds in the same area of Florestal, Brazil, had similar injuries, suggesting that such attacks may be more common than expected.  

We tend to think that birds prey on wasps, but the opposite can happen, says Thiago Moretti, a forensic entomologist in Campinas, Brazil, who was not involved with the work. Wasps are known to visit birds’ nests to get a protein-rich snack of parasites, such as mites or fleas, that dwell on the birds, he says. The insects also scavenge carrion. But they rarely attack living vertebrates, he says (SN: 6/21/19). With a vulnerable bird, “it is a matter of opportunity.”

Researchers caught the killing while filming nests to study the parental behavior of lined seedeaters (Sporophila lineola). “It was totally unexpected,” says Sjoerd Frankhuizen, a zoologist at Wageningen University & Research in the Netherlands. Upon finding the wounded nestling, Frankhuizen and his team suspected a reptile, larger bird or possibly ants, since the body was left behind. “We really had no idea that it would be a wasp,” he says.

A. pallipes lives in big colonies, so you wouldn’t expect one to take down a nestling on its own, Frankhuizen says. During this encounter, though, the lone attacker made 17 visits during the roughly hour and 40 minutes of video, possibly making multiple trips to carry bits of the bird to its own nest, he says.

Researchers have observed that many bird species nest near wasps’ nests. The birds may benefit from the wasps’ aggressiveness in defending their colonies, says Bruno Barbosa, an ecologist at Universidade Federal de Juiz de Fora in Brazil who was not part of the work. Birds attacked by a different predator may agitate the insects, “causing the wasps to attack everything around them in order to defend their colony.” And that may indirectly defend the birds.