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In contrast, each crow stood its ground and waited for the high-quality, delayed reward (meat) over the immediate, less preferred option (apple) in all three test conditions.

Co-lead author Dr. Rachael Miller, Senior Lecturer in Biology at Anglia Ruskin University, said, "Delayed gratification, in this case declining an immediate, small food reward and waiting for something better, demonstrates the ability for self-control. We have also used this rotating tray task to comparably measure self-control in young children.

"Both the Eurasian jay and the New Caledonian

crow are capable of delaying gratification for a better reward, and we expected both species would wait for the higher-quality, preferred reward when alone and potentially with a non-competitor bird present, but would choose the lower-quality, immediate reward when a competitor was present, as waiting could risk them losing out.

"Interestingly, we found that jays were highly flexible in their use of delayed gratification, and this was entirely influenced by the presence of other birds, but the crows consistently chose the better, delayed reward, regardless of rival birds being present.

"These findings add to our understanding of self-control and the factors influencing delayed gratification in animals, which may relate to a particular species' social tolerance and levels of competition.

"New Caledonian crows tend to be more sociable and tolerant of others than Eurasian jays, and while both hide food for later use, jays rely more on this tactic for their survival. This might explain why the more territorial jays altered their choosing strategy when competitors were present and selected the immediate, less preferred food to avoid missing out entirely."