The increasingly appetising buffet provided for garden birds, from sunflower hearts to suet cakes, is supporting a rising number and greater diversity of species in Britain’s urban areas, according to research.
In the 1970s, half of all birds using garden feeders belonged to just two species, the sparrow and starling, but by the 2010s the number of species making up the same proportion had tripled, with goldfinches, woodpigeons and long-tailed tits soaring in number because of the food on offer.
At least half of British homeowners feed garden birds and researchers writing in Nature Communications found they support 133 bird species – more than half of the country’s species – and are reshaping urban bird populations.
While many typical garden birds such as robins, blackbirds, chaffinches and great tits have maintained a steady presence at urban feeders, others once rarely seen in gardens have been lured in by treats such as fat balls and high-energy insectivorous mixes.
Goldfinches were spotted at just 8% of feeders in 1972 but by 2012 were seen at 87% of them. Woodpigeons were seen at 17% of feeders in 1972 and 88% in 2012. Long-tailed tits were found at 19% of feeders in 1972 and 77% 40 years later.
Other birds to have significantly increased their visits to feeders between 1972 and 2012 include great spotted woodpeckers, magpies, pheasants and nuthatches. The provision of bird food in winter has also helped migratory species, such as the blackcap, endure the British winter. Blackcaps have only become a winter resident since the 1950s.
Another bird benefiting from feeders is a species that eschews sunflower hearts for the hearts of the feeding birds: the predatory sparrowhawk, which was seen at less than one in 20 garden feeders in 1972 but at more than half of them 40 years later.
Researchers believe that garden feeders are causing changes in urban bird populations – and not simply revealing them – because feeder-using species are increasing in urban settings, whereas the populations of birds that do not use feeders, such as kestrels, yellowhammers and mallards, remain unchanged.
Lead author Kate Plummer of the British Trust for Ornithology said that, while some people might be uneasy about humans reshaping wild populations, the increasingly sophisticated feeding effort was a positive thing.
“We are substituting food we’ve taken away elsewhere, such as spilled grain from the less tidy farms of the past,” she said. “Sparrows are declining and if they can take advantage of food we are providing in our gardens, and if we provide the best food we can and keep the feeders clean, then hopefully we are doing something good overall.”
One species adversely affected by feeders has been the greenfinch, whose population has fallen because of trichomonosis, a disease that has been shown to spread at feeders.
Plummer and her colleagues also looked at the growth of bird food into a multibillion-pound industry in the decades since the 1970s. They found that the number of garden bird food products advertised in the RSPB members’ magazine increased from fewer than 10 in 1973 to more than 110 by 2005. Niche foods, such as sunflower hearts and fat balls, first appeared in the 1990s as bird-feed businesses diversified their range to attract more species – and sales.
More democratic feeder designs have also helped. Only tit species could cling to the old-fashioned wire peanut feeders, but feeders with perches have made it easier for other birds to access the food.
With a growing number of people feeding birds all year round, rather than just in winter, another report calculates that British people provide enough additional food to support 196 million birds, far more than the estimated 71 million common garden birds in the UK. According to Plummer, this excess food is likely to be supporting grey squirrels and other unintended beneficiaries.
Article Source: The Guardian