Souls in skulk shriekers consuming on shrieks

As we can see, there are two souls in the skulk shriekers. I think when the shrieker shrieks, one soul will go away in a soul particle and escape the schrieker. Once there is no more souls, the schrieker can no longer schriek and a mob needs to die near by for it to regain a soul. If the schrieker is placed by a player, there will be no souls in it, so it wouldn't summon the warden, but if the player wants it, he can kill mob arround it.

To solve the problem of shriekers having no more souls in ancient cities because no mobs can spawn here, shriekers that has naturaly spawned sould have an infinite amount of souls because, as we know, a lot of mobs has died in the ancient cities. The catalyst generated ones should only have one sould : the one of the mob that generated them.

I think this could also reinforce the idea of the skulk beeing a parasite, so when a mob dies, its soul goes into the shrieker and its experience in the catalyst, so the skulk only grows to the detriment of other life form...