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How crows and jays have different attitudes to food when other birds are around

Two similar species of birds that are capable of showing self-control through delayed gratification behave very differently around their favourite food when they company, new research has shown.

The study, led by researchers from Anglia Ruskin University (ARU) and the University of Cambridge compared the behaviour of two species of corvids: Eurasian jays (Garrulus glandarius) and New Caledonian crows (Corvus moneduloides).

New Caledonian crow. Picture: Martina Schiestl
New Caledonian crow. Picture: Martina Schiestl

They are both highly intelligent species from the same family, but the researchers found jays will settle for an immediate, less preferred food option when another bird is present, while crows will always hold out for their favourite food, regardless of the social context.

The researchers used a rotating tray task, where birds were presented with two choices - a low and high-quality option, which they had to remove from under clear plastic cups.

For jays, the high quality food was mealworm, while the low-quality food was bread. The crows’ favoured food was meat, while the less preferred option was apple.

The birds - tested separately - watched both food types added to the rotating tray while a second bird - a competitor or non-competitor - remained in an adjacent compartment.

This second bird was granted access just before the less preferred food option became available on the rotating tray. The bird being tested could choose the option in front of them, or wait 15 seconds for the delayed, preferred option.

Each jay favoured the delayed reward of mealworms if alone, but typically grabbed the immediate food choice - bread - if a second bird was present.

By contrast, each crow waited for the high-quality, delayed reward of meat over apple in all three test conditions.

Eurasian jay. Picture: Rachael Miller
Eurasian jay. Picture: Rachael Miller

Co-lead author Dr Rachael Miller, senior lecturer in biology at ARU, 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.”

The open access article was published in the journal PLOS ONE at https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0289197.

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