Clever Eurasian jays plan for the future
Experiments with Eurasian jays have shown that the birds store food that they will want in the future - "planning" for their impending needs.
The study revealed that birds would stash more of the foods that they knew would be unavailable to them on forthcoming foraging trips.
Jays are not the first birds to show that they might have the capacity for what is known as "mental time travel".
But previous claims that birds "plan" in this way have been controversial.
The findings are published in the journal Biology Letters.
- Jays are members of the corvid family
- A favourite food for these colourful birds is acorns, which they cache throughout autumn and unearth during the winter
- A single bird can bury several thousand acorns each year, so jays play a crucial role in the spread of oak woodlands
To find out if the jays thought about the future, the scientists exploited the birds' habit of hiding or "caching" food for later.
In previous studies on Eurasian jays' distant relatives, scrub jays, Prof Nicola Clayton from the University of Cambridge showed that when the birds were offered so much of one food that they became sick of it, they would still store it away in their cache.
She and her team interpreted this to mean that the birds knew they would want that food in the future.
"The difficulty though, is that we don't know what they know, we only know what they're doing," explained Lucy Cheke, a researcher who works with Prof Clayton and who carried out this latest experiment.
The scrub jays, Ms Cheke explained, might just have worked out which foods stored well and which did not. With their new experiment, the scientists wanted to eliminate the possibility that the birds were using this simple rule.
To do this, the researchers put four adult jays through their intellectual paces in a complicated four-day test.'Sick of peanuts'
On day one, the jays were presented with two differently coloured boxes in which to hide food. They could gather this from from a mixed pile of peanuts and raisins.
The following day, the scientists fed the birds only with raisins, then offered them just one of their boxes. On day three, the birds were given a pile of peanuts before being presented with the other box.
"The day after that, they came to cache again," explained Ms Cheke, "and just before they cache, they're fed a big pile of peanuts.
"So when they come to cache, they're sick of peanuts.
But instead of ignoring the peanuts and only stashing the raisins, the birds appeared to plan ahead. They stored raisins in the tray they were offered after their "peanut binge" and peanuts in the one they were offered after being fed raisins.
"Imagine a child is packing two lunch boxes - one for this afternoon and one for tomorrow," Ms Cheke explained.
"If this afternoon they know they'll get to eat loads of cake before their lunch, they'll know only to pack sandwiches in that lunch box."
The Cambridge team and their colleagues who work with corvids are continuing to reveal remarkable insights into their intelligence.
Ms Cheke is currently investigating Eurasian jays' social abilities - finding out if the birds are able to understand how other birds are feeling.Follow the ants
Other researchers based in the same Cambridge laboratory have found examples of what they think is mental time travel in wild birds.
Some bird species in Costa Rica follow army ant swarms through the forest, indulging in an insect feeding frenzy as flying insects flee the ant raid.
Researcher Corina Logan has observed birds checking ant bivouacs - the temporary nest structures that the ants construct at the end of their raid.
She and her colleagues proposed, in a paper in the journal Behavioural Ecology, that the birds might return to the nest sites the following day, in order to follow the next ant raid.
Ms Logan told BBC Nature: "I think [this behaviour] could possibly involve future planning.
"The birds were checking bivouacs when they were not hungry, a behaviour that does not make sense until the next morning."
Ms Logan says that studying animals in the wild like this helps researchers make sense of their cognitive abilities "in the context of their social and ecological environment".
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