Polly Dips Her Crackers In Water, Like People Dipping Theirs In Coffee

Goffin’s cockatoos are the first parrots found to alter hard foods by dipping them in water, possibly to improve the texture

If you live with a parrot, then you know these clever birds can invent all sorts of novel behaviors. Such was the situation for a team of veterinary researchers based at the Medical University of Vienna and the University of Vienna. These researchers, Jeroen Zewald, a PhD Candidate in Veterinary Medicine under the guidance of Alice Auersperg, a cognitive biologist specializing in understanding the evolution of intelligence in birds, keep and study the behaviors 0f a flock of captive Goffin’s cockatoos.

Goffin’s cockatoos, Cacatua goffiniana, are also known as the Tanimbar corella or the Tanimbar cockatoo for the Indonesian island archipelago where they are endemic. These parrots are the smallest of the white cockatoo species, and are often confused with the Solomon Islands (Ducorps’) cockatoos, Cacatua ducorpsii, so they were not scientifically recognized as their own separate species until they were formally described in 2004 (ref). Although Tanimbar corellas are classified as a Near Threatened species in the wild by the IUCN due to depredations by the cage bird trade and habitat destruction due to deforestation, they have been successfully introduced to Indonesia’s Kai Islands, Puerto Rico and Singapore, and there also is a large avicultural population throughout the world.

Mr Zewald and Professor Auersperg recently reported that some of their cockatoos were dunking their hard toasted bread bits into water, apparently to improve the texture. Although never before reported amongst Tanimbar corellas, dunking food into water prior to eating it is not unheard of: many animals, most notably humans and racoons, and at least 25 bird species, dunk their food, although why they do so remains a mystery.

This peculiar behavior was first noticed by accident when a male cockatoo, Pippin, who is known for both his cleverness and his mischievous ways, picked up a piece of rusk and headed to a nearby water bowl, normally used for bathing. Once there, he pushed the bread underwater and held it there for several seconds. He then removed it from the water and ate it.

Rusk, or zwieback, is a type of twice-baked bread that is dry and brittle. It is commonly given to human babies when they are teething. But it is also part of the daily rations of food provided to the lab’s captive Goffin’s cockatoo flock, along with seeds, bird pellets, dried fruit and cornflakes.

After this initial observation, Mr Zewald and Professor Auersperg then observed several of the cockatoos in the flock imitating Pippin’s actions, varying in both their dedication to the task and the amount of time they dunked the bread.

After watching the cockatoos eat over a 12-day period, Mr Zewald and Professor Auersperg saw that 7 of the 18 birds in the lab dunked their food — and the dunked food was almost always rusk (Figure 1). Two of the most prolific dunkers preferred to eat wet rusk. Dried banana chips and dried coconut chips were also occasionally dipped in water (Figure 2), but the cockatoos 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,” Mr Zewald and Professor Auersperg wrote in their study.

The birds left the bread in the water for an average of 23 seconds, more than enough time to soften its texture. They also found that some of the cockatoos were willing to go to great lengths to soak their bread before eating it, sometimes climbing ladders and even moving obstacles out of their way.

The seven cockatoos who regularly dunked their food 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 Mr Zewald and Professor Auersperg’s own rusk-dunking experiments.

Researchers have suggested five main motives for dipping food in water prior to eating it: washing off dirt, improving the flavor, drowning prey, transporting liquid away like a sponge or texture improvement.

The lack of live prey rules out the possibility the cockatoos were trying to drown their food, and nor were they trying to increase their fluid intake because water was always freely available.

“Seasoning behaviour also seems implausible as they dunk food in fresh, unflavoured tap water,” Mr Zewald and Professor Auersperg write in their report, adding the pickiness of the birds about which foods they dunked — they never dunked seed, for example — suggests they were not trying to wash the food. For this reason, the researchers speculated that the cockatoos probably dunked the rusks to soak them, which might improve its texture.

“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,” Mr Zewald and Professor Auersperg pointed out in their paper.

This behavior requires impulse control and delayed gratification, and highlights the ingenuity of the cockatoos in a food preparation context.

The research team originally noticed this behavior in three of the lab’s cockatoos, so they were not sure whether the cockatoos developed food dunking independently or learned it after watching each other.

So far, food dunking has not been observed in wild Goffin’s cockatoo populations, possibly due to a lack of open water or soakable food. Therefore, this appears to be a foraging innovation amongst these captive cockatoos. Alternatively, Mr Zewald and Professor Auersperg could fully exclude the possibility of seven individuals preferring soaked food while the rest of the population prefers dry, which could also explain the limited number of individuals dunking.

Previously, it has been suggested that innovating dunking behavior is relatively simple in captivity where the circumstances are favorable — available food, an open water source nearby, and a minor risk of the food being stolen). This could also explain why relatively more caged birds dunk (60%) than in the aviary (31%).

“This dunking behaviour requires several components of primordial forms of planning such as impulse control and temporal discounting to actively produce a qualitative benefit,” Mr Zewald and Professor Auersperg write in their study. “It also once more reflects the innovativeness of this parrot species, now also in a food preparation context.”

Already, the researchers are watching to see whether or how this behavior spreads throughout in rest of the flock.

Source:

J. S. Zewald and A. M. I. Auersperg (2023). Dunking rusk: innovative food soaking behaviour in Goffin’s cockatoos (Cacatua goffiniana), Biology Letters 19(12) | doi:10.1098/rsbl.2023.0411

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