Songbird Foils the Notorious Cuckoo By Moving to Suburbs

The Daurian redstart, a migratory songbird living throughout much of Asia, has learned to avoid its cheeky nemesis, the cuckoo, by moving closer to human developments.

The cuckoo, a notorious “brood parasite,” lays its eggs in other birds’ nests so that it doesn’t have to expend resources on raising its young. The unwitting foster parents, like the Daurian redstart, will feed and nurture the bastard chick as its own, even as it matures into a very different-looking bird (photo shows cuckoo, mouth wide, with a mother redstart). If you’ve ever wondered where the term “cuckold” comes from, now you know.

The redstart has learned to mitigate the threat of this parasitism by moving its nests closer to people. Cuckoos shy away from humans but redstarts don't mind them so much. Scientists from the Max Planck Institute for Biological Intelligence teamed up with colleagues from Beijing Normal and Beijing Forestry Universities to document this strange adaptation.

Daurian redstarts breed twice per season, before and after cuckoos show up in the region. The researchers observed that redstarts moved their nests closer to human settlements for the second egg-laying period, presumably to avoid the cuckoos. They tested the hypothesis by piping in cuckoo calls to mimic the parasites before they arrived in the area, and sure enough, the mimicry caused the birds to move, and always toward where people live.

The scientists also found that the risk of getting cuckolded increased with the distance between the nest and the nearest people, showing that Daurian redstarts have developed a truly novel adaptation strategy. Now the researchers are wondering how, not if, the cuckoos will adapt. Parasites are good at it too.

Photo credit: Jinggang Zhang / Biological Intelligence