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.