Feed the birds?

What do birds like eating and what decisions do they have to make when visiting a bird feeder? Not quite tuppence a bag - Brits spent around 200 million pounds a year on bird food. But what do birds like eating and what decisions do they have to make when visiting a feeder? Lindsay visits her mum's garden to get some close-up shots, Friederike Hillemann tells us about her research in Wytham Woods and Annette Fayet explains how puffins face similar problems.