There are many types of birds with excellent vocabularies. A male budgie currently holds the world record for the largest avian vocabulary. African greys, macaws and amazons are excellent talkers, and are probably the most well-known for their skills. But most species of parrot can learn to talk, just not all of them have a loud and clear voice. Lots of birds have a very soft and/or gravelly voice so when they do talk it's hard to understand, or you don't even realize they're talking! Now, if they *will* talk is the better question. I have heard of people with Greys that didn't talk, and I have also seen videos of lovebirds and cockatiels (not well known as talking species) talking a little. But there are generalizations that tend to be true in most cases.
Birds generally learn to talk by imitating and repeating phrases they hear a lot. That is why you see so many videos on youtube of parrots saying things like "Hi!" "Who's a pretty boy/girl/baby?" "I love you", their own name, etc. If consistently worked with, some birds can and do learn and understand some words and rearrange them to create their own sentences that they've never heard before.
The only retail stores around here with resident birds are pet stores, so I'm afraid I'm not much help regarding parrots in shoe stores...
When you say "long-lived", exactly how long are you thinking? 20 years? 50 years? 80+ years? Some cockatoos and macaws have been known to live older than 100, but not by much and it is not too common since most people did not know how to care for birds until very recently; even today, the majority of bird-keepers are not properly caring for their birds.
I am not sure what you mean by "very wise". Generally the birds don't go around answering the mysteries of life.

Good luck with your book!