What is the equivalence of a parrot's IQ in terms of human age?

It depends on the individual bird involved. Just like humans, some parrots are smarter than others; some learn things quicker than others, etc. In general, a parrot has the intelligence level of about a 1- or 2-year-old human child. If you observe parrots over a long period of time (years), you'll find that most are very intelligent... they have to be in order to survive.