Google research has indicated macaws love or eat a lot of Brazil nut. These are highly toxic to humans in somewhat small quantities due to their selenium content.

Given the mass difference between a human and macaw, lets say 80kg and 2kg, if toxicity for humans 'starts' around 900micrograms or ~9 nuts, maths would indicate toxicity for a macaw might be around 20% of a nut?

These figures are all based on google and the margin of error I expect is quite large, nonetheless it seems quite disparate if a macaw could consume even a single nut a day on average, without consequence?

  • $\begingroup$ I know that macaws congregate around mud banks and eat mud (maybe clay?) I wonder if this might have something to do with it. $\endgroup$
    – Karl Kjer
    Commented Aug 10, 2018 at 13:13
  • $\begingroup$ @KarlKjer Not according to this, though I don’t know how trustworthy it is. $\endgroup$
    – canadianer
    Commented Aug 10, 2018 at 16:43
  • $\begingroup$ this is good article but about amazona parrrots. The clay is really good call. But it detoxicate only quinidine by 60%. $\endgroup$
    – L.Diago
    Commented Aug 10, 2018 at 17:29
  • $\begingroup$ Interesting question. You should consider, though, that the excretory system in birds is quite different from mammals. For example, they have two different types of nephrons. You've assumed the toxic dose is proportional to mass. It's not. You have to account for differences in kidney function, even in humans. $\endgroup$
    – De Novo
    Commented Aug 10, 2018 at 19:13

1 Answer 1


One explaination is that macaws (Ara sp.) eat clay and other food item which absorb the toxins. Here is the full answer from Wikipedia:

Like all macaws and most parrots seeds and fruit are the major part of the diet of the genus Ara. The particular species and range of diet varies from species to species. Unlike many birds macaws are seed predators not seed dispersers, and use their immensely strong beaks to open even the hardest shells. Their diet overlaps with that of some monkey species; in one study of green-winged macaws in Venezuela they shared many of the same trees as bearded sakis, although in some cases they ate the seeds at an earlier stage of ripeness than the sakis, when they contained more poison. Macaws, like other parrots, may consume clay to absorb toxic compounds produced by some poison...but with further research we now at last know it is just to eat life saving sodium that is missing. As well, the toxic compounds of some foods may be neutralized by compounds, such as tannins, found in other foods consumed at the same time...but we have found that it is untrue and really just to gain access to sodium missing otherwise in their diet because of the area they live in.

Source: Wikipedia - Ara (genus)

  • $\begingroup$ Your premise Is bad. Selen Is not ONLY toxin And your answer actually doesnt answer thé question. However with that clay Is actually quite good call but i didnt find any information on selen but other chemicals such as quinidine. $\endgroup$
    – L.Diago
    Commented Aug 16, 2018 at 5:21

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