Storks reintroduced in Japan grow steadily but challenges remain

This autumn marks 20 years since the beginning of an effort to release artificially bred oriental white storks back into the wild in Japan.

The once extinct animal's breeding grounds have since expanded to 13 prefectures, including Ibaraki, Kyoto and Saga, with the population in the wild growing to 558 as of late August.

The oriental stork is found in East Asia and Siberia. The large migratory bird has a wingspan of about 2 meters.

However, the birds went extinct in Japan due to a combination of factors including overhunting, loss of habitat, industrialization and urban development, and the decline of their food sources caused by modern farming practices like widespread use of pesticides and chemical fertilizers.

The last wild individual in Japan died in Toyooka in 1971, marking the species' extinction.

Artificial breeding and reintroduction programs were implemented across the country after the species went extinct in Japan in 1971. The species is classified as critically endangered on Japan's Environment Ministry's Red List, indicating an extremely high risk of extinction.

Hyogo Prefecture and Toyooka City launched the reintroduction project in 1992. The initiative was sparked seven years earlier when six juvenile storks were adopted from Siberia. Breeding and rearing continued at the Hyogo Park of the Oriental White Stork with the goal of "returning extinct storks to Japan's skies".

Back to sky

The birds were first reintroduced to the wild on Sept 24, 2005. Five birds were selected from a breeding population of over 100 as the first step toward reintroduction. Each was fitted with a radio transmitter on its back to track how far they flew and where they settled.

The project team used the data from the transmitters to understand the birds' distribution. The team continued releasing the remaining birds, taking genetic diversity into account. By autumn 2023, a total of 59 birds had been released back into the wild, with reintroduction projects also conducted in Fukui and Chiba prefectures.

In late June, four chicks fledged from an artificial nest on a tower facing Lake Kasumigaura in Ibaraki, the second largest lake in Japan. It was the third consecutive year of successful natural breeding in the city.

Oriental white storks typically migrate to areas rich in fish, frogs, insects and other prey.

"The chicks perhaps took a liking to the abundant natural environment of Lake Kasumigaura and surrounding areas," a city official said.

"When we reintroduced the first birds, I worried they might die quickly," said the park's former keeper Minoru Funakoshi, 61, who was involved in the 2005 reintroduction.

Back then, Funakoshi was busy traveling nationwide whenever breeding was confirmed, attaching leg bands to chicks before they fledged.

"It is wonderful to see the population grow this much," he said. "I hope they become birds cherished by the Japanese."

Competition for sites

In recent years, chicks have been born across a wide area that is rich in food, such as rice paddies. However, the growing population has given rise to concerns over competition for breeding sites.

"They could expand their habitat to the Tohoku region and Hokkaido, where rice farming is thriving," said Takayuki Funo, 48, the Hyogo Park of the Oriental White Stork's chief researcher.

Many bird species build their nests on utility poles and other structures, posing a risk of electrocution. The modern farming methods, which favor higher rice yields, reduced the populations of frogs, fish, and other small organisms that the storks depended on.

Tomohiro Deguchi, an associate professor of University of Hyogo, said, "Local governments are urged to take the lead in ensuring abundant feeding grounds, such as by leaving rice paddies flooded during winter and reducing pesticide usage."

Takuma Kaito, a senior ranger from the Kyushu Regional Environmental Office, said, "Our goal is for the animals to survive stably in their natural state, but we are still far from achieving that."

The Japan News