Why Are Sparrows Disappearing in Japan? The Bird That Needs a Gap in the Roof
For people in Japan, the sparrow, suzume, is the most ordinary bird there is. It hops along rice field edges, waits under the eaves, and appears in old folk tales such as The Tongue-Cut Sparrow. Yet over the past few decades, many people have started to say the same thing: there are fewer sparrows than there used to be.
They are right. Japanese researchers have measured it, and the reasons point back to something very close to home: the way we build our houses and keep our gardens.
We are a small tree care and landscape business in Mie Prefecture, central Japan. We also make and put up nest boxes for wild birds. This page explains what is happening to Japan's sparrows, and what a garden can do about it.
Japan's sparrow is not the house sparrow
If you are from Europe or North America, the sparrow you know in towns is probably the house sparrow. Japan's town sparrow is a different species: the Eurasian tree sparrow, Passer montanus. You can tell it by its chocolate-brown cap and the black spot on each white cheek.
In Britain, the tree sparrow is a bird of the countryside, found on farmland and nesting in holes in old trees. In Japan, the same species lives right beside people, in villages, towns and city streets, nesting in the holes and gaps of our houses.
How much have they declined?
In 2009, ornithologist Osamu Mikami gathered every kind of count he could find, from crop damage records to bird ringing data, and published an estimate in the journal of the Ornithological Society of Japan. His conclusion: the sparrow population had fallen to roughly 20 to 50 percent of its level around 1990. Compared with the 1960s, it may be only about one tenth.
Long-term monitoring has since confirmed the trend. Monitoring Site 1000 is a national survey run by Japan's Ministry of the Environment, in which local volunteers count species at 325 rural sites. Its report covering 2005 to 2022 found that 16 of 106 bird species were declining at a rate of 30 percent or more per decade. That is fast enough to meet the criteria for Japan's endangered species list. The sparrow was one of them.
What makes this striking is that the sparrow is not a rare bird. It is not on any red list. It is a common species slipping away while it still looks common.
A bird that needs a gap
Sparrows in Japan nest in small gaps in buildings: under roof tiles, in gaps in wooden walls, inside the ends of pipes. Traditional Japanese houses, with clay tile roofs and wooden boards, were full of such gaps.
Modern houses are built to be airtight. A study published in 2013 by Osamu and Katsura Mikami compared sparrow nests in housing areas built at different times, in Iwate and Saitama prefectures. Nest density in neighbourhoods built around 1970 was 3.8 times higher than in neighbourhoods built around 2000 in Iwate, and 4.8 times higher in Saitama. The researchers concluded that newer houses very probably leave sparrows with nowhere to nest.
A bird that cannot fly far for food
The second half of the story is food. According to Dr Mikami, sparrows feed within about 100 metres of the nest. A pair needs a place to nest and a place to find food close together: grass seeds, insects for the chicks, a hedge to hide in.
In many towns, one or the other has gone. Old houses with gaps are rebuilt, and gardens are paved over for parking or covered with weed sheets and gravel. Even where a sparrow can still nest, there may be nothing to feed its chicks within reach.
What a garden can do
This is where our work as gardeners comes in. A few things help.
Keep some low cover. A hedge or a group of shrubs gives sparrows somewhere to rest and hide from crows and cats.
Leave a little untidiness. A patch of grass allowed to set seed, or a corner where insects can live, is food within 100 metres.
Use fewer pesticides. Sparrow chicks are raised largely on insects.
Put up a nest box. Tree sparrows will use boxes. A Japanese study of sparrow nest boxes found that they preferred an entrance hole of about 30 to 31 millimetres, and that boxes hung anywhere between about 1.4 and 3.7 metres above the ground were used equally. If your garden has a sparrow nest under the roof, remember that in Japan wild bird nests with eggs or chicks are protected by law. Wait until the young have left before closing the gap.
The quiet loss
When a rare species declines, people notice. When a common bird declines, it happens in the background. Researchers in Japan describe this as the loss of ordinary nature, the birds and butterflies of fields and gardens that nobody thought needed protecting.
In our work we see it at the level of a single garden. A hedge that is kept, a tree that is pruned instead of removed, a nest box on an old trunk. None of these will bring back the sparrows of the 1960s on their own. But a sparrow lives its whole life within a few gardens, so a few gardens can make a difference to it.
