For those who find it convenient to cling onto beliefs that there's a magical distinction between the consciousness of an animal and that of a human - probably because this makes it easy to ignore the plight to which we subject animals - The Economist presents this obituary of Alex, a parrot, aged 31:
By the end, said Dr Pepperberg, Alex had the intelligence of a five-year-old child and had not reached his full potential. He had a vocabulary of 150 words. He knew the names of 50 objects and could, in addition, describe their colours, shapes and the materials they were made from. He could answer questions about objects' properties, even when he had not seen that particular combination of properties before. He could ask for things—and would reject a proffered item and ask again if it was not what he wanted. He understood, and could discuss, the concepts of “bigger”, “smaller”, “same” and “different”. And he could count up to six, including the number zero (and was grappling with the concept of “seven” when he died). He even knew when and how to apologise if he annoyed Dr Pepperberg or her collaborators.
A human comparison: in Richard Lynn's Race Differences in Intelligence, there is a page about how certain human languages (spoken by human races with the lowest IQs, such as bushmen and the Australian aborigines) can only express numbers with the words "one", "two", "few" and "many". In some of these languages, numbers more than 2 can be expressed by chaining multiple "two" and "one" together, e.g. "two two one" = 5. However, this works only up to about seven, at which point the chain of twos gets too complex for the listeners to understand.

These people have average IQs of about 50-60. That makes one wonder about a possible IQ overlap between the most intellectually challenged types of humans and the average Alex-like parrot.

And it also makes one wonder about lots of other things.