In the month of April, more than 200 birds have been found poisoned to death in Dongsheng Nature Reserve, a “refueling station” for migratory birds in Baoqing County, Heilongjiang province, northeastern China. Among the poisoned birds were species considered threatened by the International Union for Conservation of Nature, such as the lesser white-fronted geese, mallards, and Baikal teals.

Birds that stop at the Dongsheng Nature Reserve are on their way from warmer climates back to their breeding grounds in northern Asia and Siberia.

On April 18 alone, more than 180 dead geese and ducks were found. Liu Hongqin, chief of the Baoqing County forest police department, told Sixth Tone’s sister publication The Paper that the birds were poisoned from eating corn kernels laced with carbofuran, a pesticide toxic to birds. The forest police suspects someone deliberately scattered the corn at locations in the nature reserve where birds were likely to stop during migration.

The Baoqing Forestry Bureau used farming equipment, including rotary tillers, over a 3-acre area to make sure any poisoned corn kernels would be buried deep underground.

“Migrating birds are so smart that it’s not going to work if someone just puts poison in a random area,” said Huang Ximin, a local bird protection volunteer. “These geese and ducks were targeted.”

On Thursday, The Paper reported that 11 suspects had been caught. According to local police, the suspects, dealers in rare animals, have admitted to poisoning the birds.

A Chinese version of this article first appeared on The Paper, a sister publication of Sixth Tone.

(Header image: A dead mallard found on farmland in Dongsheng Nature Reserve, Heilongjiang province, April 18, 2016. Quan Yi/Sixth Tone)