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.

Clay Licks of Amazon Rainforest

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.

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. This layer was found to have much higher levels of sodium than those above and below.

Clay Licks of Amazon Rainforest

Red-and-green macaws at a clay lick in Manu National Park. Photo credit: Dustin & Lori Slater/Flickr

Donald Brightsmith, who led the Tambopata Macaw Project, pointed out that parrots outside the western Amazon region also consume foods that contain toxins, such as the seeds of Hura crepitans, or sandbox tree, yet it’s only those in the western Amazon basin who visit these clay banks, indicating that parrots can go by with a little toxin in their stomach without the need to consume clay to detoxify themselves. Rather, Brightsmith argues that there’s a connection between this clay-eating habit and the fact that the western Amazon basin is exceptionally lacking in salt. Research by Alan Lee et al. support this finding. Lee showed that clay-eating in parrots is positively correlated to a significant degree with distance from the ocean, suggesting that the lack of nutrients and not food toxicity is the driving force behind this behavior.

Where to see clay licks?

Clay Licks of Amazon Rainforest

Distribution of known parrot claylicks in South America. Image courtesy: Alan Lee

There are many dozen sites in Paraguay, Peru, Bolivia, Brazil and Ecuador in the Amazon rainforest where clay licks occur, but the most popular and accessible sites are located in Tambopata National Reserve in southeastern Peru.

Another popular spot to witness the colorful congregation of parrots is the Blanquillo Clay Lick in Manu National Park, also in Peru. The licks at Yasuni National Park, in Ecuador is another hot spot catered to tourists.

Clay Licks of Amazon Rainforest