Should we feed garden birds during the breeding season?
People who feed birds during the spring could unintentionally be harming them, a new study from the University of Reading has revealed.
Researchers found that putting food out for birds during the breeding season makes it five times more likely that bird nests near the feeders will be raided by predators such as grey squirrels. This is because predators are also attracted to the food, and then explore nearby vegetation, where nests are located.
The study's findings come despite contradictory advice by British bird charity the RSPB, which advises feeding birds all year round to help them survive during periods of food shortage.
Corresponding author of the published study Professor Mark Fellowes, head of Biological Sciences at the University of Reading, said: "Feeding wild birds is a fantastic way to connect with nature and has many benefits for both birds and people, but our research shows that if we're not careful we may accidentally cause harm."
"Our study has revealed if we really want to help our garden birds, during the breeding season we should make sure that feeders are located well away from potential breeding sites, so that we don't inadvertently increase nest predation."
More than half of UK households put out food for wild birds like blue tits, robins and goldfinches, providing a vital resource for their survival in urban areas, especially during the winter months.
But as the snow melts and spring comes, birds begin laying eggs in nests, which are vulnerable to predators like grey squirrels, magpies and jays.
Reading researchers carried out more than 100 tests, placing artificial nests containing quail eggs 5 and 10 metres away from hanging peanut feeders. These were either empty, filled with food, or fitted with a guard preventing access by nest predators.
Only 10% of the nests near filled feeders survived, compared with just under 50% of those near empty feeders.
Interestingly, just as many nests were raided near feeders with predator guards, despite the guards greatly reducing the amount of visits by grey squirrels and magpies. Unexpectedly, jays were also found to take eggs, seemingly using similar tactics to find the nests.
Doctoral researcher and lead author Hugh Hanmer said: "The importance of jays was unexpected, as they didn't visit feeders but as clever corvids it's likely that they're foraging near where they see other species feeding."
However, Professor Fellowes emphasised that feeding birds should still be encouraged, if people are mindful of the potential consequences.
Professor Fellowes said: "We'd just recommend that people should take care during the breeding season if nest predators are being attracted to their gardens. The easiest solution is to place feeders well away from potential nest sites, or to provide food which is less attractive to squirrels and magpies.
"While our research suggests guards do not stop nests being discovered, they do greatly reduce how much food goes to nest predators such as squirrels, which helps ensure that the food provided benefits the species people wish to feed."
3 January 2017
Journal reference: Hugh J. Hanmer et al. Provision of supplementary food for wild birds may increase the risk of local nest predation, Ibis (2017). DOI: 10.1111/ibi.12432
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