The Clay Licks of Amazon Rainforest

Macaws and parrots of the Amazon rainforest have developed a particular taste for clay. They collect in large numbers on exposed river banks to peck at the dirt, creating a dazzling spectacle that entertains thousands of onlookers. Red-and-Green Macaw at a clay lick in the Peruvian Amazon Rainforest. Photo credit: jorgeluizpsjr/Shutterstock.com But why do these birds eat clay? One of the most accepted theory is because they lack sodium in their diet. Sodium is needed for a multitude of bodily functions such as generation of nerve impulses, for maintenance of electrolyte balance, for heart activity and certain metabolic functions. Many herbivores whose diet is completely plant-based require extra salt as plants do not contain enough salt in them. So animals often obtain sodium from salt licks. Clay and soil is a good source of sodium, as well as many other nutrients such as potassium and magnesium. Another theory is that the birds eat clay to get rid of toxins, that they ingest from plants, from their bodies. When they eat clay, the clay particles bind to naturally occurring toxins such as quinine and tannic acid, preventing them from getting absorbed by the gastrointestinal tract. Related: The Salt Mining Elephants of Mount Elgon However, research seem to suggest that the sodium theory is more correct. The Tambopata Research Center (TRC) in Peru studied the clay eating behavior of parrots at clay licks in Peru, and found that the soils the birds choose to consume do not have higher levels of cation-exchange capacity, i.e. the ability to absorb toxins, than that of unused areas of the clay licks. Rather, the birds prefer soil that have higher levels of sodium. At one clay lick site, on a particular bend of the Manu River, researchers observed parrots eating one specific layer of soil which runs hundreds of meters horizontally along that bend. The parrots avoided eating the layers above and below the preferred layer.