This is a slight mystery, but researchers point to urban sprawl and modern styles of architecture that have deprived the birds of their natural habitat and their usual nesting places in towns and cities, as well as a lack of food, particularly insects.
According to the researchers, the number of sparrows in Japan has fallen by 60 percent in over the past 21 years. 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 Yamahsina 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 Ministry of the Environment.
The institute has 31 designated monitoring sites. All birds flying over these areas are captured. Approximately 70,000 birds were captured annually at these locations for analysis from 1987 through 2008. Initially, about 4,000 sparrows were among the total count, or approximately 6 percent. But in recent years, the number has fallen to about 1,000 or less than 2 percent.
Furthermore, after analyzing a tendency of each place generally, and inspecting it with regard for considerations of fluctuation, the team concluded that the number of sparrows in Japan has fallen by about 60 percent in 21 years.
Before this latest work, Mikami had estimated a 50-80 percent decline since 1990. This estimate is 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. "It is clear that the number of sparrows keep dropping."
It used to be common for sparrows to build their nests under the eaves of traditional Japanese houses. But changes in house design, and a paucity of food in urban areas, have led to loss of their habitats. This has resulted in fewer chicks, contributing to the sharp decline in sparrow populations.
The team continues researching it in detail.
Image Credit: Lip Kee/CC BY-SA 2.0
Hiroshi Nomaki, Japan correspondent for American Daily Herald, studied law at Kanagawa University and writes from Sagamihara, Kanagawa Prefecture near Tokyo.
Copyright © 2012 Hiroshi Nomaki. Used with Permission.
