This photo shows a sparrow. The number of sparrows in Japan is on the decline, according to a recent survey. (Photo courtesy of Osamu Mikami, professor at Hokkaido University of Education's Hakodate Campus)

       The Mainichi Shimbun answers some common questions readers may have about the decline of sparrow and swallow populations in Japan.

       Question: I've heard there was a major bird survey released recently. What was it?

       Answer: That would be the Japan Breeding Bird Atlas survey, also known as the national bird census, and it was the first time it has been released in about 20 years. It showed that the number of sparrows in the country has fallen by 34% since the 1990s, and that of swallows has decreased by about 40%.

       Q: Why have their populations declined?

       A: Although the cause of the decline is not clearly understood, it seems that they have been severely impacted by human activity. According to Osamu Mikami, a professor at Hokkaido University of Education's Hakodate Campus who is researching the sparrow population decline, the birds need suitable places to nest and enough food to live.

       Nests are usually built under the eaves of houses or in gaps in tile roofs, which are difficult for predators to get into. Recently, however, more square houses with no eaves and no roof joints are being built.

       Q: Is it also getting harder for the sparrows to find food?

       A: In addition to a decrease in farmland, vacant lots and wooded areas close to residential areas, as well as green spaces at temples and shrines, are disappearing, making it difficult for the birds to find the seeds and insects that make up the core of their diet. Sparrows do not typically stray more than about 100 meters from their nests. It's likely that the number of places where the birds can find both good nesting sites and enough food are decreasing.

       Q: Are humans also responsible for the decline in swallows?

       A: Swallows also build nests under the eaves of houses and feed on insects in open green spaces such as farmland, so their situation is like that of sparrows in that suitable living environments are increasingly difficult to find.

       Q: Will the number of swallows and sparrows keep shrinking?

       A: Although they are not yet at risk of extinction, their numbers may continue to decline. Mikami said, "I hope that this survey will help people realize that the nature around us is being lost."

       (Japanese original by Tomoko Mimata, Science & Environment News Department)

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