Cheerios should NEVER EVER EVER be fed to birds because of its high iron content but, to put the icing on the cake, it has now been found to have high levels of carcinogen insecticide which has been banned in many countries but not USA (and it's not that we haven't been trying real hard but Congress will not do anything about it even when the courts have found that it's real bad for people).
https://thenutritionwatchdog.com/glypho ... -cheerios/