Parrots, as biologists and bird owners alike will tell you, are sloppy eaters. Whether in the wild or as pets, the birds often fling their food, drop chunks of it on the ground, and generally make a mess at mealtime.
This slovenly behavior has been widely observed and discussed, but had never been quantified, says Esther Sebastián-González, an ecologist at the Universidad Miguel Hernández in Spain. So, she and colleagues decided to take an empirical look to see what might be behind this apparent food waste. “Something that is so widespread in the group, and has been maintained over the evolutionary history of the group, is probably because there's some benefit for the birds,” she says.
Now, after a research project spanning five continents and over a hundred species of parrots, Sebastián-González and team report that messy eating seems to be universal among this group of birds. And they suspect the behavior might be more than mere clumsiness, and not so wasteful after all—it could be an intentional practice akin to farming.
The new study, recently published in Scientific Reports, compiled results from a decade of field notes, camera trap records, and experiments done with parrots in captivity. Combining these techniques, the scientists were able to cover about one-third of all parrot species.
Their findings removed any doubt that parrots are a messy bunch. Every species in the study was found to waste fruits, flowers, seeds, and other foods. Some, such as the Crimson-bellied Parakeet, a parrot native to the Amazonian rainforest, dropped more than half of the food they picked. Parrots sometimes ate part of the food before tossing the remainder, but they also frequently dropped morsels before even trying to eat them.
That last observation led the scientists to believe the behavior may be intentional, and they have some ideas about why parrots might purposely drop uneaten food. Removing unripe and low-quality fruits—pruning, essentially—can force plants to put more energy into what remains, producing sweeter, juicier fruit. Farmers commonly prune crops like apple and cherry trees, cutting off fruiting buds or even entire branches. Similarly, the researchers found that parrots dropped unripe foods more often than ripe ones, just as you’d expect from an expert orchardist.
Pruning could work to the birds’ advantage in other ways, Sebastián-González notes. It can lengthen a plant’s fruiting season, increasing access for the parrots to particular types of fruits. And it can induce fruiting in plants that typically don’t produce fruits every year. “Maybe the parrots are thinking ahead and thinking that this pruning of the tree can be beneficial for them in the future,” she says.
The idea of forward-thinking parrots isn’t as far-fetched as it might seem. Last year scientists studying delayed gratification in parrots found that they were willing to forgo a snack of dry corn to instead accept tokens they could later trade for a tastier tidbit of walnut or sunflower seeds. It’s worth noting, though, that the parrots in that study only had to wait several seconds for the preferred food—far from the weeks or months of foresight that the parrot-farmer hypothesis would require.
Not all scientists are convinced that there’s intent behind parrots’ sloppy eating. The behavior might simply be a result of living in lush environments with abundant food to choose from, says Laurie O’Neill, a biologist at the Max Planck Institute for Ornithology who was not involved with the new study. Parrots have powerful beaks and dexterous feet that make plucking and splitting open fruit quick and easy. Since it doesn’t take much additional time to sample a range of foods, parrots can afford to be picky, says O’Neill. Ultimately, their physiology allows them to still eat the same amount of food, but from a wider variety of sources, giving them a more balanced diet, he explains.
Regardless of whether it’s intentional, pruning by parrots has benefits for the forests they inhabit. For example, the extra fruit left to rot on the forest floor recycles nutrients back into the soil. The fruits and seeds dropped from treetops also allow ground-dwellers access to food they otherwise couldn’t reach. And these animals additionally help the plants by spreading seeds to new areas.
While this redistribution can increase diversity in a forest, it could also spread invasive species: In the study, parrots dropped food from non-native plants more frequently than native ones. That could be because they have a shorter evolutionary history with these plants and therefore have had less time to adapt to handling them, the researchers report. Then again, they say, it might just be an effect of the environment, as invasive species tend to be found near humans, whose presence might spook parrots, causing them to drop more food.
It’s also too early to say if parrots drop some food on purpose. Sebastián-González plans to look for such intent by studying, for example, whether some of the birds have longer breeding seasons that can be linked to extended fruiting triggered by parrot pruning. Her continued research may help sort out whether parrots are truly forward-looking farmers, or just a bunch of sloppy eaters.