By Victoria Gill
Science reporter, BBC News
Birds can learn to choose the best building materials for their nests, according to scientists.
It was previously thought that birds' choice of nest material was determined by their genes - with each type of bird having an "innate nest template".
But an experiment has now shown this to be a more cognitively complex activity.
The study, published in the Royal Society journal Proceedings B, involved giving finches a choice of floppy and stiff string to build their nests.
"We found that zebra finches like the stiffer string," explained lead researcher Dr Ida Bailey from the University of St Andrews.
"It's more efficient for them to build with - they can build a nest with fewer materials."
Dr Bailey and her colleagues were looking to test the learning ability of birds; their test aimed to work out if the birds could learn to differentiate between materials based on their properties.