We documented an adult Lesser Cuckoo Cuculus poliocephalus killing nine-day-old Japanese Bush Warbler Cettia diphone nestlings by ejecting them from their nest. Among the available hypotheses concerning brood-parasitic birds destroying host nest contents, only the ‘farming hypothesis’ helps to explain this case, although the attack did not force the warbler to immediately re-nesting because one nestling survived. Considering the long breeding season and frequent re-nesting habit of the Japanese Bush Warbler, as well as the delayed arrival of the Lesser Cuckoo into the breeding area, such predatory behavior seems to be effective in creating replacement clutches for future parasitism.