For what it is worth in this conversation.  I had a Blue Crowned conure(parrot) for 30 years.  He clearly understood the meaning of about 10 words.  Night Night when he wanted to go to bed for example.  He did not say but understood Thats Hot when I was feeding him.  But also he had a sense of humor.  He would laugh at appropriate times.  For example, I was re-tiling my kitchen floor.  His cage was in the living room in clear site.  He was sitting quietly(rare) for a few hours while I was working.   I stood up and had left a cabinet door open, and banged my head hard.  He suddenly burst out laughing.  Some might say he was just mimicking.  That might be true but that asks the question, isn't all language just a mimicking of what we have heard and associating a meaning to it?  I know TLDNR.