Macaws and mealy amazons at a clay lick in Tambopata National Reserve, Peru
Macaws eat a variety of foods including seeds, nuts, fruits, palm fruits, leaves, flowers, and stems. Wild species may forage widely, over 100 km (62 mi) 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.
Donald Brightsmith, the principal investigator of the Tambopata Macaw Project, 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.
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.
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 B
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Diet and clay licks[edit]
Macaws and mealy amazons at a clay lick in Tambopata National Reserve, Peru
Macaws eat a variety of foods including seeds, nuts, fruits, palm fruits, leaves, flowers, and stems. Wild species may forage widely, over 100 km (62 mi) 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.
[12]
In the western Amazon hundreds of macaws and other parrots descend to exposed river banks to consume clay on an almost daily basis
[13]
– except on rainy days.
[14]
Donald Brightsmith, the principal investigator of the Tambopata Macaw Project, 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
[15]
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.
[16]
Sodium is a vital element that is scarce in environments greater than 100 kilometres from the ocean.
[17]
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.
[18]
Salt-enriched (NaCl) oceanic aerosols are the main source of environmental sodium near coasts and this decreases drastically farther inland.
[19]
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.
[19]
Studies at TRC have shown a correlation between clay-lick use and the breeding season.
[20]
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 B
12
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