The industry body, UK Pet Food, estimates that we spend some £380 million a year on bird food. Separate figures suggest that amounts to more than 150,000 tonnes annually – enough to sustain three times the breeding populations of the ten commonest garden species if they relied on it alone all year round.
Source: https://www.bbc.com/news/articles/c2lwvz1pl1no?at_medium=RSS&at_campaign=rss