Why "Phantom Bird" Kingfishers Returned to Upscale Neighborhoods in Central Tokyo

Why Did the Kingfisher Disappear from Central Tokyo?

The kingfisher has bright cobalt blue and orange colors and a long beak, and because of its jewel-like beauty, its name is written with the kanji (Chinese characters used in Japanese writing) for "jade." They live near water throughout the year, diving into the water to prey on fish, shrimp, crabs, and aquatic insects.

Professor Yanase says, "During the Covid pandemic, I could not travel far so I started to go on walks around my neighborhood. That was when I spotted a kingfisher from a bridge and was captivated by its beauty and style. I started going to other rivers to look for them and found a kingfisher couple living together. Since then, I have been observing and studying them."

According to a survey in 1968 by the Wild Bird Society of Japan, the only place in Tokyo where the bird could be seen was to the west, deep in the mountains of the Okutama area.

"The reason was clear. Environmental pollution caused by the rapid economic growth of the postwar period made the rivers uninhabitable for the kingfisher's food sources such as fish and shrimp. Carp can survive in somewhat polluted rivers, but even they were gone. Take the Meguro River, for example. It is now famous for its cherry blossoms, but I well remember from when I was living in Ebisu near Shibuya that, at that time, the river smelled like a drainage ditch due to factory and household wastewater, and nobody came to see cherry blossoms. It was inevitable that kingfishers left the city center for the countryside in search of food."

Emergence of the "New Wild"

Why are kingfishers returning to the heart of the city then?

"The answer is simple: the rivers in the city center have become clean enough for fish to live in. The environment has improved. In fact, along the Kanda River on my walking route, I can see the Haguro damselfly with its pitch-black wings and beautiful metallic green body. They only live around clear streams. This shows just how much the water quality has improved."

However, the creatures that inhabit the rivers in the city center today are not the same as in the past.

"Many of the native species in urban rivers have become almost extinct due to pollution during the period of rapid economic growth. The most prolific species that kingfishers feed on now is the cherry shrimp, a non-native species from China that was released as fishing bait. The same goes for the American crayfish. There are also very few freshwater fish, other than carp released by fishery research centers, and most are brackish water species such as mullets and gobies that can travel between the sea and freshwater."

Professor Yanase describes the situation as the "new wild," where such non-native species and brackish-water fish have increased in the rivers of central Tokyo. This has led kingfishers in search of food to return. Another important factor is the habitable environment.

"Kingfishers normally dig nesting holes on riverbanks with their long beaks. However, riverbanks in central Tokyo have been reinforced by concrete. But if you look closely, you will see that there are pipe holes for drainage. Kingfishers use those holes for nesting. This might be easier and more comfortable for them because they do not have to dig their own holes.

The "Old Wild" Still Remains

But why did the returning kingfishers choose upscale residential areas? The answer lies in spring water.

"Tokyo has always had many springs because it sits on the Musashino Plateau. Parks and green areas were created around spring-fed ponds and have been well maintained and preserved. Tokyo is one of the largest cities in the world, but still has abundant nature and greenery."

Since ancient times, people have gathered and fought for water and used the surrounding area as a sphere of influence.

"Back in the Edo period (1603-1868), powerful lords built their residences in parts of Tokyo with springs and left vast areas of greenery. Powerful figures in the Meiji era continued to live around springs, leading to the development of the upscale residential areas that exist today. Spring water ponds tend to have clean water, and it was around those ponds where kingfishers returned in the 1980s when the rivers were still dirty."

These so-called "old wild" areas still remain in Tokyo. One example is the Shibuya River. It is believed to have its source in a spring in Shinjuku Gyoen National Garden, one of the city's largest green spaces, and flows through upscale residential areas. Though its name changes from section to section, kingfishers live year-round along its tributaries like the one in the park at the National Museum of Nature and Science's Institute for Nature Study in Minato City.

Tokyo's Major Attraction

"The largest green space in central Tokyo is the Imperial Palace. Former Princess Kuroda Sayako  studied the ecology of kingfishers that had returned to the Palace while a researcher at the Yamashina Institute for Ornithology when she was still a member of the Imperial Family," Professor Yanase says.

To him, one of Tokyo's major attractions is that the old wild remains and co-exists with the new wild, which is centered around non-native species and brackish water fish. He also has an idea of what to do next: "Now that the rivers have been cleaned up, I would like to see initiatives to connect the old wild and the new wild closer together by systematically releasing native fish species with the help of biologists."

Yanase Hiroichi

Born in 1964. After graduating from Keio University with a degree in economics, he joined Nikkei McGraw-Hill (now Nikkei Business Publications, Inc.). He has worked as a Nikkei Business reporter, book editor, and producer of Nikkei Business Online Edition. Professor at the Institute for Liberal Arts, Tokyo Institute of Technology since 2018. In 2023, he received the Seiichi Tejima Research Award for his book National Highway Route 16: The Road that Created 'Japan'.

Video of a kingfisher in central Tokyo shot by Professor Yanase.

Operating on the concept that envisions green urban development for the next 100 years, the Tokyo Metropolitan Government is pushing initiatives to protect, increase and maintain, and cultivate Tokyo's greenery.
By promoting initiatives like the creation of a biodiverse community, its efforts aim to transform Tokyo into a sustainable city that exists in harmony with nature.
https://www.metro.tokyo.lg.jp/english/policies/environment/0804_01.html