s at a clay lick in Tambopata National Reserve, Peru Macaws eat a variety of foods including seeds, nuts, fruits, palm fruits, leaves, flowers, young shoots, and stems. Safe vegetables include asparagus, beets, bell peppers, broccoli, butternut, carrots, corn on the cob, dandelion greens, collard greens, hot peppers, spinach, sweet potatoes, tomatoes and zucchini. Wild species may forage widely, over for some of the larger species such as
Ara araurana (blue and yellow macaw) and
Ara ambigua (great green macaw), in search of seasonally available foods. Some foods eaten by macaws in certain regions in the wild are said to contain
toxic or
caustic substances which they are able to digest. It has been suggested that parrots and macaws in the
Amazon Basin eat clay from exposed river banks to neutralize these toxins. In the western Amazon hundreds of macaws and other parrots descend to exposed river banks to consume clay on an almost daily basis – except on rainy days. Donald Brightsmith, the principal investigator of
The Macaw Society, located at the Tambopata Research Center (TRC) in Peru, has studied the clay eating behaviour of parrots at clay licks in Peru. He and fellow investigators found that the soils macaws choose to consume at the clay licks do not have higher levels of
cation-exchange capacity (ability to absorb toxins) than that of unused areas of the clay licks and thus the parrots could not be using the clay to neutralize ingested food toxins. Rather, the macaws and other bird and animal species prefer clays with higher levels of sodium. Sodium is a vital element that is scarce in environments greater than 100 kilometres from the ocean. The distribution of clay licks across South America further supports this hypothesis – as the largest and most species-rich clay licks are found on the western side of the Amazon Basin far from oceanic influences. Salt-enriched (
NaCl) oceanic aerosols are the main source of environmental sodium near coasts and this decreases drastically farther inland. Clay-eating behaviour by macaws is not seen outside the western Amazon region, even though macaws in these areas consume some toxic foods such as the seeds of
Hura crepitans, or
sandbox tree, which have toxic sap. Species of parrot that consume more seeds, which potentially have more toxins, do not use clay licks more than species that eat a greater proportion of flowers or fruit in their diets. Contents of nestling
crop samples show a high percentage of clay fed to them by their parents. Calcium for egg development – another hypothesis – does not appear to be a reason for
geophagy during this period as peak usage is after the hatching of eggs. Another theory is that the birds, as well as other herbivorous animals, use the clay licks as a source of
cobalamin, otherwise known as vitamin B12. == Relationship with humans ==