Why do macaws eat dirt? It is not to neutralize toxins as once thought.

Nature · Published 29 September 2026 Swipe more like this →

In short: For years, scientists believed macaws visited river banks to eat clay to neutralize toxins from their diet. New research at the Tambopata Research Center in Peru reveals a different truth: these vibrant parrots are actually hunting for sodium, a vital nutrient scarce in the deep interior of the Amazon basin.

Macaws are a group of 19 species of large, long-tailed New World parrots belonging to the tribe Arini. They are defined by their zygodactyl feet, proportionately large beaks, and unique facial feather patterns that act like fingerprints. While they are native to Central, North, and South America, their populations are currently threatened by rapid deforestation and illegal trapping.

The mystery of their clay-eating behavior, or geophagy, has long intrigued researchers. While it was once hypothesized that the birds consumed clay to absorb toxins from their food, studies by Donald Brightsmith and colleagues at the Tambopata Research Center found no evidence that the chosen soils had superior toxin-absorbing capabilities. Instead, the data suggests that macaws target clays rich in sodium. Because sodium is essential for biological function and becomes increasingly rare more than 100 kilometers from the ocean, these inland birds must seek out mineral-rich licks to survive.

This behavior is particularly pronounced during the breeding season, with nestlings receiving high amounts of clay from their parents. Beyond their ecological habits, macaws have a long history of human interaction. Pre-Columbian civilizations, such as the Ychsma in Peru, went to extraordinary lengths to secure their feathers, transporting live birds across the Andes mountains to coastal sites. Today, these birds remain subjects of intense study and conservation, with international trade strictly regulated by CITES to prevent further population declines.

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