The behaviour suggests the potential for 'state-attribution' in these birds -- the ability to recognise and understand the internal life and psychological states of others.

The research was carried out in Professor Nicola Clayton's Comparative Cognition lab at Cambridge University's Department of Psychology, and is published February 4 in the journal PNAS.

Researchers tested mated jays and separated males from females. The females were fed one particular larvae, either wax moth or mealworm -- a treat for the birds, like chocolates -- allowing the males to observe from an adjacent compartment through a transparent window.

Once the pairs were reintroduced and the option of both larvae was presented, the males would choose to feed their partner the other type of larvae, to which she hadn't previously had access -- a change in diet welcomed by the female.

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