Sparrow populations in Japan are plummeting, just as they are in Europe.
Quite why remains something of a mystery, but researchers point to urban sprawl and modern styles of architecture that have deprived the birds of their natural habitat and usual nesting places in towns and cities, as well as a lack of food, particularly insects.
Sparrow numbers in Japan have fallen by about 60 percent over the past two decades, the researchers say.
The estimate by a team at Rikkyo University in Tokyo and Iwate Medical University in Iwate Prefecture is based on the results of monitoring by the Yamashina Institute for Ornithology.
Gen Morimoto, a researcher at Rikkyo University’s Lab of Animal Ecology, and Osamu Mikami, an assistant professor of biology at Iwate Medical University, are members of the team.
They used data from the institute to quantify a suspected decline in sparrow numbers after ornithologists and bird-watchers raised the alarm.
The institute tracks the migration of birds through bird ringing, attaching tags to legs, to gauge their numbers. The nationwide project is overseen by the Environment Ministry.
The institute has 31 designated monitoring sites. All birds flying over these areas are captured for analysis.
Between 1987 and 2008, roughly 70,000 birds were captured annually at these locations.
Initially, about 4,000 sparrows were among the total, or approximately 6 percent. But in recent years, the number has fallen to about 1,000, or less than 2 percent.
After taking trends in populations across the country into account, along with periodic fluctuations and other factors, the team concluded that sparrow numbers have fallen by about 60 percent over 21 years.
Before the latest undertaking, Mikami had projected a 50-80 percent decline since 1990 based on a trajectory of sparrow numbers in some areas and the number of birds killed by farmers to protect their crops.
The team’s findings confirmed that sparrows are quickly vanishing, not only in urban areas but also in monitoring sites set up in rich natural surroundings.
“We reached the same conclusion on the sparrow decline even after we computed the bird’s population with statistics that we had not used before,” Morimoto said. “Sparrow numbers keep dropping. That’s what we know for certainty.”
In years passed, it was common for sparrows to build nests under the eaves of traditional Japanese homes. But changes in home design, and a paucity of food in urban areas, have led to the loss of their habitats.
This has resulted in fewer chicks, contributing to the sharp decline in sparrow populations.
MASAHIRO YONEYAMA / Staff Writer