Hi Julie,
I am so sorry to hear about your friend’s Amazon. As far as I know, the shredders are safe – they are made from a natural palm leaf I believe. The dyed ones are newer but they use bird safe dyes. I am not aware of any string being used with this toy. It is very rare for parrots to eat a foreign object simply because of the way they eat. But some will consume toy parts or other things they should not.
Foreign objects can stay in a bird’s digestive system for a very long time. I participated in a necropsy once of a macaw that had never fully thrived with the owner, who had purchased him from a breeder nearly 20 years prior to his seemingly sudden death. His proventriculus was packed with small pieces of what we at first thought was brick but soon realized was pieces of lava rock. The owner had never provided one to her birds, but she remembered the breeder had one in every cage. So this rock sat for 20 years, never digesting further, but affecting the bird’s health as far as taking up room in the proventriculus. It is very possible this Amazon consumed the threads a long time ago and they had only recently passed through to the intestines. The most common source of threads is usually from cage covers or something near the cage that the bird gets into. Since this could have been some time ago, your friend may have forgotten or even not known about this depending on when she got the bird, or if the bird was ever boarded anywhere.
I know this doesn’t change anything, but again, I don’t think it was the toy.
Take care,
Brenda