Very Curious Bluejays

We've had Bluejays around our back yard for many years. This was the first year that a pair has nested in a secluded corner of our yard, producing offspring. We've been observing the antics of the juvies, and as they mature, they're sort of surprising. Very loud, hanging on the feeders, and creating a huge racket. I'd read that these birds mimic other sounds, and I wonder if they're "practicing", finding their voices. They're just everywhere, screaming in from all directions. The whimpering puppy sound is amazingly convincing, until one realizes it's coming from the top of a tree. I'd appreciate any knowledgeable comments on Bluejay puberty. Am attaching a couple of photos as examples.

My tiny scrap of knowledge:
Bluejays are noisy except while they are nesting - then they are stealthy, seldom seen or heard. At my house, the change is very noticeable both before and after. Although they have a reputation for preying on the nests of other birds, often other birds will nest near bluejays - theory is that Bluejays are a good defense against predators, so the rewards outweigh the risks.
A favorite sound to imitate is hawks. One theory is that they do it to scare other birds away from a favorite food source. I have wondered if they are teaching their young about Hawks. Or maybe they have a weird sense of humor.