Humans are not the only beings who sometimes like a soggy snack: researchers have discovered some cockatoos also dunk their food before eating.
The team say they first noticed captive Goffin’s cockatoos dunking their grub during a lunchtime feed, much like some people dip biscuits in their tea, and decided to explore further.
Writing in the journal Biology Letters, researchers at the University of Vienna describe how they placed the birds’ food – twice-baked bread known as rusk, dried pieces of fruit, seeds and bird pellets – into bowls inside their aviary in the presence of tubs of water.
Over the course of 12 days, the team recorded which birds dunked, what the dunked item was, how long it was dunked for and if it was subsequently eaten.
Overall the team found seven out of the 18 cockatoos dunked their food at least once, with rusk the most popular item. Two of the most prolific dunkers showed rusk was preferentially eaten wet. Dried banana chips and dried coconut chips were also occasionally dipped in water, but the duo tended to prefer them dry.
“The behaviour seemed to be mainly targeted at rusk, a dry and hard food type that easily absorbs water and adopts a soggy texture,” the team write.
The researchers found the seven cockatoos showed considerable variation in how long they left their pieces of rusk in the water, although some left them long enough for the core to go soft – according to the team’s own rusk-dunking experiments.
The team say the lack of live prey rules out the possibility the birds were trying to drown their food, while freely available water makes it unlikely they were dunking to gain fluid.
“Seasoning behaviour also seems implausible as they dunk food in fresh, unflavoured tap water,” they write, adding the pickiness of the birds about which foods they dunked suggests they were not trying to wash the food.
As a result, the team say the birds probably dunked the rusks to soak them, a strategy they say might improve its texture.
The researchers say the behaviour requires impulse control and delayed gratification, and highlights the ingenuity of the birds in a food preparation context.
“Because only some individuals dunked food and dunking has not been observed in the wild, we believe this to be a spontaneous foraging innovation either by one or multiple individuals,” they write.
Prof Simon Reader of McGill University in Montreal, who was not involved in the study but worked on dunking by wild Carib grackle birds, said it was surprising the behaviour had not been scientifically documented in parrots before.
“We found that dunking was very rare in the wild in Carib grackles, but it was less innovative than we thought – virtually all birds could do it if you placed them in perfect conditions, with dry food, water, and away from the risk of the food being stolen,” he said.
“Like these parrots, dunking seems to be something they employ depending on the costs and benefits at the time.”