For many years, different authors and observers have highlighted the regular consumption of clay by psittacidae in the heart of the Amazon forest (viewed at first in Manu National Park). Filmed sequences have been shown on many television channels. Dr Don Brightsmith conducted observations in south eastern Peru along the Tambopata River in the heart of the Amazon forest. In the early morning, the clay cliffs are covered by hundreds of psittacidae (blue-and-yellow macaw, red-bellied macaw, chestnut-fronted macaw, mealy parrot, yellow-headed amazon, dusky-headed parakeet, white-eyed parakeet, white-bellied parrot, etc.).

 

Dr Don Brightsmith observes that "[…] the fear of the unknown, the fear of being the first one to land was so great it kept the birds flying for nearly 10 full circles in front of the lick. The wheeling flock passed within a few feet of the lick, but still did not land. Then on the next pass it happened: three of the lead Red-bellied Macaws landed alertly on the lick. They sat fully erect scanning for the slightest sign of danger. […] As the morning progressed the numbers on the lick slowly diminished as the parrots got their fill of the special soil and dispersed in to the vast wilderness of the Tambopata Reserve Zone and the Bahuaja - Sonene National Park."

 

In Peru, these clay cliffs are known by the Quechua¹ word colpa (often written collpa or ccollpa), which loosely translates to "salty earth." The cliffs that psittacidae regularly visit are along river banks.

 

Why do they consume clay soil?

 

For quite some time, several hypotheses have been advanced:

• Ingest more mineral salts,
• Protect themselves from toxins in their diet.

 

In the wild, parrots often eat not yet ripe seeds, thus hindering the natural fertilisation of trees. Trees "protect themselves" by making their seeds more or less toxic even when their fruit is perfectly edible.

 

The mystery was recently solved by James Gilardi (director of the World Parrot Trust):

 

He demonstrated that parrots prefer to consume clay soil and in particular that which contains kaolin². Clay particles have the distinction of being negatively charged, while most toxic plant compounds have a positive charge. This type of clay soil binds with toxic alkaloids ("chelation"). Thus, bound toxic compounds are never absorbed by birds’ intestinal mucosa. The "coating and insulating" presence of clay on the walls of the digestive system also protects the birds from tannin derivatives.

 

Lastly, it seems that parrots prefer "the saltiest clay soil, because they do not consume clay with little salt yet which contain the same quantities of clay. Parrots look for soil which protects them from toxic derivatives and which give them their sodium their physiology needs" (Dr Don Brightsmith).

 

Who eats clay soil?

 

Many animal species eat soil from clay walls (also called salt walls). These species include pigs, squirrels, monkeys, deer, etc.

 

The following parrots have been observed eating clay.

 

In Africa:

• African Grey Parrot

 

In New Guinea:

• Large and medium-sized sulphur-crested cockatoo (C.galerita)
• Eclectus (Eclectus roratus)
• Palm cockatoo (Probosciger atterimus)
• Pesquet's parrot (Psittrichas fulgidus)
• Rainbow lorikeet (Trichoglossus h.haematodus)

 

In South America:

• All parrotlets
• All conures (Aratinga+Pyrrhura)
• Blue-headed parrot (Pionus menstruus)
• White-bellied parrot (Pionite leucigaster)
• Macaws

A mystery remains: scarlet macaws and mealy parrots have never been observed consuming soil in Central America, while in Peru they have. To our knowledge, no explanation has yet been given.

 

The following links and sources cited in this article draw on the research of James Gilardi and Dr Donald Brightsmith:

 

- Gilardi, James et al, Biochemical function of geophagy in parrots. Journal of Chemical Ecology 25:897-922.

 

- Bird Talk, October 2003, Dr Don Brightsmith, The real dirt on parrot clay licks, page 50-57.

 

¹ South American Indian language, which was the language of the Incan Empire.

² Kaolin is used in pharmaceuticals (in the form of hydrated aluminum silicate) to protect the coating of the gastric mucosa and to alter intestinal flora.