However, in 2012 the taxa were recognized as separate species by BirdLife International on the basis of genetic, morphological, plumage and vocal differences.

They feed primarily on palm nuts, seeds, fruits, and leafy matter, but have also been observed eating snails.

The genus Psittacus was introduced in 1758 by the Swedish naturalist Carl Linnaeus in the tenth edition of his Systema Naturae.

[14] The Guinness Book of World Records listed a grey parrot that allegedly lived in captivity for 72 years as the longest-lived specimen for the species.

[15] The grey parrot (Psittacus erithacus) has been known at times to contract a non-infectious inflammatory lung disease called lipid pneumonia.

[21] Birds appear to offer, in their behavior, neurophysiology, and neuroanatomy a striking case of parallel evolution of consciousness.

[citation needed] Irene Pepperberg's research with captive greys, most notably with a bird named Alex, has scientifically demonstrated that they possess the ability to associate simple human words with meanings, and to intelligently apply the abstract concepts of shape, colour, number, zero-sense, etc.

[23] As well as labeling objects, Alex could verbally express what his wants were, suggesting that grey parrots know the difference between features and feelings.

[24] In general, it has been shown that grey parrots are able to learn relatively quickly, though they are limited to simple and non-abstract mediums of thinking.

[29] A study published in 2011, led by Dalila Bovet of Paris West University Nanterre La Défense, demonstrated grey parrots were able to coordinate and collaborate with each other to an extent.

Throughout the day they spent time in a room with toys and came into fairly regular contact with the humans taking care of them.

The noises that these parrots could hear consisted of the calls of canaries in the laboratory, people cleaning, doors squeaking, etc.

[34] More rare than previously believed, the grey was uplisted from a species of least concern to near threatened in the 2007 IUCN Red List.

[37] The grey parrot is listed on Appendix II of the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES).

This review has resulted in recommended zero export quotas for several range states and a CITES decision to develop regional management plans for the species.

In the United States, importation of wild-caught grey parrots is prohibited under the US Wild Bird Conservation Act of 1992.

However, the same qualities mean they require a special commitment by their owners to provide frequent one-on-one interaction and supervised time out of their cages.

Greys require large cages, varied diets that include fresh foods, and plenty of safe and chewable toys.

Despite this, there is a long history of these parrots being kept at pets by the ancient Greeks, wealthy Roman families, King Henry VIII, Portuguese sailors, and others.