For a fictional canine witness (sort-of), we have the Sherlock Holmes story of the dog that didn’t bark. (Silver Blaze)
As someone who has kept multiple birds for 20+ years now I have to disagree with this. All my good talkers were brought as babies into a household where there already birds, some of whom never spoke human words at all.
Here’s the truth: the parrot family are highly social animals, even more so than human beings. If you want your bird to talk with human words you need to interact with the bird. Lots and lots of one-on-one time. They can hang with the rest of the flock the rest of the time, but if you want a talker you and the bird in question have to be the focus of each other’s attention for hours at a time. They’re going to try to communicate with anyone in their social circle, not just other birds. (My green cheek conure has been trying desperately for 10 years now to engage the microwave in conversation, viewing it as a source of yummy food and may be thinking he can sweet-talk it into being more generous. After all, it works with the hairless bipdel apes he lives with.)
Not all birds learn to talk. Some birds learn to talk and then you can’t shut them up. (2 am calls of BABY BIRD! PRETTY BIRD!, Imitating the phone and/or microwave, etc.). Some birds just randomly throw out words and phrases. Some learn to use words and phrases in context. Some do best with immediate reward for tricks. Others don’t require rewards, just attention. (They can be vain little “look at me! look me!” brats.)
In other words, not only do different species vary in their ability to speak in a human manner, individual birds also vary in that ability. About the only decent predictor is that the males tend to be better talkers than the females, but there are plenty of exceptions to that rule, too.
Irene Pepperberg (of Alex the African Grey Parrot fame) finds that parrots use vocal mimicry to compete with one another for the attention of a third party.
Thus, to teach a parrot to talk most effectively, you don’t talk to that parrot. You talk to someone else. Get two people in a room and have them talk at each other, ignoring the parrot, saying things you want the parrot to learn. The parrot will start saying those things to compete for attention.
Cite: She talked about this at a presentation at Sea World / Africa USA some time ago (circa mid-late 1980’s as best I recall), where a bunch of animal language researchers were invited to give a public talk about their work. Some of the well-known chimp language researchers gave talks there too, and at least one dolphin language researcher (Diana Reiss).