It is a scourge straight out of Hitchcock, and the crows here look and act the part. With wing spans up to a yard and intimidating black beaks and sharp claws, Japan’s crows are bigger, more aggressive and downright scarier than those usually seen in North America.

Attacks, though rare, do happen. Hungry crows have bloodied the faces of children while trying to steal candy from their hands. Crows have even carried away baby prairie dogs and ducklings from Tokyo zoos, city officials said.

Image A member of the Crow Patrol of Kyushu Electric Power in Kagoshima, Japan, looking for nests that are often found on poles. Credit... Ko Sasaki for The New York Times

While no one knows the precise number of crows in Japan, bird experts and government officials in cities across the nation say populations have increased enormously since the 1990s. Tokyo says the number of crows it has counted in large parks rose to 36,400 in 2001 from 7,000 in the late 1980s, prompting a trapping plan that cut the numbers to 18,200 last year. However, ornithologists say that the actual number in Tokyo is closer to 150,000 birds, and that some crows may have moved to different areas to avoid the traps.

Behind the rise, experts and officials say, has been the growing abundance of garbage, a product of Japan’s embrace of more wasteful Western lifestyles. This has created an orgy of eating for crows, which are scavengers. Some steps taken to reduce crows include putting garbage into yellow plastic bags, a color the birds supposedly cannot see through, and covering trash with fine-mesh netting, to prevent large beaks from reaching the goodies within.