It’s a party in your garden and everyone’s invited Kay Roxby / Alamy Stock Photo

Putting bird feeders in your garden really does help, according to a UK study looking at the growth of bird populations in the past 40 years.

“We know that feeding happens on a huge scale in the UK, US, Australia and parts of Europe,” says Kate Plummer of the British Trust for Ornithology. “We are trying to understand what the impacts of that might be.”

Volunteers for the trust have been monitoring which species feed on the food they put out in their gardens since the 1970s. Plummer’s team analysed this data to see what changes there have been over time.

“There’s about 68 or so species that have always used feeders. They used them in the 70s and they use them now,” Plummer says. “But actually within our own gardens we are seeing a greater number of species.”

For instance, just 10 per cent of volunteers saw wood pigeons and chaffinches at their feeders in the 1970s. Now they are seen at feeders in more than 80 per cent of gardens, alongside other birds that have always been common visitors, such as robins, blackbirds and blue tits.

The team found this greater diversity rose in tandem with the increasing diversity of foods and of feeder types introduced over the decades, as revealed by adverts in bird magazines.

Finally, the team compared its findings with survey data on bird populations. It could be, for instance, that increases in population sizes have led to increases in feeder use rather than vice versa. But because in urban areas the populations of birds that don’t use feeders haven’t increased while those that do have, the team thinks the feeding is driving the increases in populations.

“It does suggest that through the use of garden bird food we can have a positive influence on populations,” Plummer says.

But people need to keep their feeders clean, she cautions. Feeders can spread disease by bringing birds into closer contact than usual. The number of greenfinches in the UK nearly halved to 2.8 million after a disease outbreak in the 2000s blamed on feeders.

Other studies suggest feeders can alter behaviour and may even lead to the evolution of new species.

Journal reference: Nature Communications, DOI: 10.1038/s41467-019-10111-5