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Wild Macaws Eat Clay


Several years ago, National Geographic published a photo essay featuring large flocks of scarlet and blue macaws (the largest parrots in the world) mobbing a clay deposit on a riverbank in Peru. The parrots were obviously eating the clay, but why?

Charles Munn, a researcher for the College of Agricultural and Life Sciences at Cornell University, traveled to the Amazon River Basin to find out. There he found large flocks of macaws at clay and mineral licks near a riverbank. After studying them closely, he concluded that each bird spends two or three hours per day there. At first, Munn thought that the macaws used the clay licks to add minerals to their diets. A graduate student, though, called his attention to the toxins in many of the seeds they ate, so Munn reconsidered the matter.

Macaws feed primarily on seeds. Munn says they are very curious, and will eat any seed, or anything resembling a seed, that they encounter. Many seeds in the Amazon River Basin, though, contain some of the deadliest of all known poisons. How, then, can the birds survive after eating them?

The clay they eat, Munn said, neutralizes the powerful tannins and alkaloids in the seeds, binding to the toxins and helping to eliminate them from the birds’ bodies.

Some Indian tribes in the High Andes region also eat clay, apparently for the same purpose.

Clay both absorbs and adsorbs organic compounds and heavy metals. Absorption is is taking matter within its molecular structure; adsorption is attracting foreign material to the outside of its particles.

Some zookeepers and breeders of exotic birds feed smectite clay to their charges. The clay in avian diets is said to:

  • improve thickness and health of egg shells
  • increase the survival rate in young birds
  • improve appearance
  • reduce psychological problems caused by confinement, lack of natural sunlight, malnutrition, stress, and overcrowding

The eating of dirt (geophagy) is fairly common among wild animals- birds especially. Birds need grit, usually pebbles or coarse sand, in their gizzards to help break down their food. The clay in the Amazon banks is extremely fine, though, with particles as small as a few millionths of an inch in diameter. Particles that fine would be useless in grinding food. The benefits from eating them, then, are mineral supplementation, restoring pH balance, or detoxification.


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