Farming Behavior by the Large Hawk-Cuckoo Toward the Silver-Eared Mesia and Black-Streaked Scimitar Babbler

Brood parasites improve their reproductive success by offloading the costs of incubation and chick-rearing onto host species. This interaction often triggers an evolutionary arms race between increasingly deceptive brood parasites and increasingly defensive hosts. According to the farming hypothesis, when suitable host nests are limited, some parasitic birds may destroy unsuitable host nests through "Farming behavior" to induce re-nesting, thereby creating new opportunities for parasitism. Despite its potential significance, this behavior has been documented in only a few brood-parasitic species. In 2024, in Jindong County, Pu'er City, Yunnan Province, southwestern China, we successfully captured video evidence of Farming behavior by the Large Hawk-cuckoo (Hierococcyx sparverioides) on its host, the Black-streaked Scimitar Babbler (Pomatorhinus erythrocnemis), and potential host, the Silver-eared Mesia (Leiothrix argentauris). On April 22, 2024, a Large Hawk-cuckoo was recorded removing a 7-day-old Black-streaked Scimitar Babbler chick from its nest, but the chick subsequently crawled back inside. On May 27, 2024, a Large Hawk-cuckoo was observed ejecting three 10-day-old Silver-eared Mesia chicks from their nest. This is the first recorded instance of the Large Hawk-cuckoo removing chicks from the nests of both the host and potential host species. The observed actions are consistent with the Farming hypothesis, suggesting that such behavior may be a more widespread yet underrecognized strategy among brood-parasitic birds.