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Crows can refrain from eating a snack if a tastier snack is on the way

A new study has demonstrated that crows can exercise anticipation and self-control, abstaining from eating a treat if they know a preferred treat is coming soon.

(Credit: Crow image by Danny Chapman, CC BY 2.0)

A new study has demonstrated that crows and ravens can exercise anticipation and self-control, abstaining from eating a treat if they know a preferred treat is coming soon.

Crows and ravens, apparently, have individual food preferences — and can exercise enough willpower to refrain from eating an inferior treat if they know they will shortly be offered a better treat. Moreover, the study — conducted by researchers in Germany and Austria and lead authored by University of Göttingen, Germany, graduate student Friederike Hillemann — found that crows and ravens would even forego a larger amount of food, trading two treats for one if the one was a favourite.

The test was based on the Stanford marshmallow experiment conducted in the 1960s and 70s, which was designed to study delayed gratification. Children were offered a choice between one small reward now, or two if they could wait 15 minutes or so until the tester returned.

First, the researchers learned the favourite foods of the seven crows and five ravens used in the study, feeding them treats such as bread, grapes, sausage, fried pork fat and other tasty titbits to see which one each bird favoured (most of them liked the meaty treats). Then, the birds were offered one of the inferior treats. After a delay — anywhere from a few seconds to 10 minutes, they were offered a choice of either a superior treat or a larger helping of the same inferior treat. The birds could take a treat or leave at any time, at which point, the treats would stop coming.

The birds, the researchers found, would wait only for the superior treats, not more of the same treat; moreover, if they had a superior treat, they would take it and go, not waiting to see if there would be more. "These crows are fed on a regular basis," Friederike Hillemann explained. "They don't have to work for their food in general, but they were still willing to wait, voluntarily — not because they were starving."

Previous similar tests on other birds, such as pigeons, parrots and chickens, have suggested that many birds lack the ability to be patient. However, all the birds in this study were bred in captivity, which may have influenced the results — living in the wild doesn't always afford the luxury of such choices.

What it does indicate, however, is that corvids are capable of assessing situations and making decisions that will achieve the best results — and, according to University of Cambridge cognitive psychology researcher James Thom, it could indicate how much harder corvids in the wild are willing to work for superior food. "In my experience, corvids will jump through quite a lot of hoops for preferred foods," he said. "I wouldn't be surprised if birds in the wild were willing to work quite hard for high-value food items as opposed to low-value ones."

Corvids, at any rate, are a bit of an avian anomaly in terms of intelligence. Just last month, we saw a crow solve a complicated eight-step puzzle to reach a piece of food.

The full study, "Waiting for better, not for more: corvids respond to quality in two delay maintenance tasks", was published in the April edition of the journal Animal Behaviour.