Geophagy: Parrots That Eat Dirt

By Keith Randall and John Holder

What kind of a bird-brain would want to eat dirt?

The answer seems to be a parrot... or at least some parrots. Dr. Donald Brightsmith, an expert on parrots in the Schubot Exotic Bird Health Center at Texas A&M’s College of Veterinary Medicine, is very interested in why certain kinds of South American parrots call soil their favorite meal. He’s interested enough, in fact, to have made many trips to southeastern Peru to look for an explanation.

Dr. Brightsmith’s usual destination in Peru is an area called Tambopata, a lowland region that is home to a 1,500-foot-long clay lick. The clay lick serves as a food source for several species of parrots, who gather there to consume the dirt every day. The parrots have other animals for company at the clay lick, including monkeys, deer and other species.

Bird specialists like Dr. Brightsmith have been puzzled by parrots’ practice of geophagy—the intentional eating of soil—for a long time. Dr. Brightsmith thinks that he has at least part of the answer: parrots eat soil for the nutrients in it, mainly sodium, and for its protective effects.

He told Texas A&M writer Keith Randall recently, “We found out that some of the soil they eat contains 40 times the amount of sodium of others in the same region. So the parrots get the salt they need and want, and the soil there also contains calcium and iron. Plus, we also believe they eat the soil for protective reasons. The soil binds to toxins in the plants they eat, and helps protect them from the harmful effects of those toxins.”

So—however the idea may sound to us non-parrots—eating soil seems to be the right choice for the birds. But here’s a mystery: Not all parrots do this, according to Dr. Brightsmith. In fact, while some parrots visit the clay licks on a daily basis, others never go near it.

The researcher has found that the parrots that do go to the clay licks make a considerable effort, traveling a long way to get to them and staying there for a long time. What’s more, they seem to make the trips in spite of nervousness about predators, which frequent the clay licks as well, hoping to prey on the birds.

But other parrots living in the same general area choose not to join the birds that visit the clay licks. Why some birds crave the licks and others don’t, Dr. Brightsmith says, is one of the important question that he and his colleagues would like very much to answer. Finding a reason for this oddity in the eating behavior of some parrots could solve some mysteries about the birds—maybe even leading to ways of stopping the shrinkage of parrot populations.

At this point around 94 species of parrots are either endangered or facing extinction. The colorful, intelligent birds have been hunted for decades for sale in the pet industry. And to make matters worse, more and more of their native rainforest habitats have been cleared for development or agriculture, which means an even greater decline in their numbers.

In fact, Peru’s government is considering reducing the size of the national park which contains the clay licks by 20 percent, in order to allow natural gas exploration and extraction. Dr. Brightsmith and other avian experts are now involved in an effort to persuade the government of Peru not to go ahead with these plans, for the sake of the clay licks and the fragile environment they are part of.

Dr. Brightsmith’s continuing work on this fascinating side of parrot behavior is funded by a grant from the Schubot Exotic Bird Health Center, the Earthwatch Institute, Rainforest Expeditions and private donors.