Blackmailing-Baby Birds

A certain idea in chapter 8 left me quite puzzled. The author was bringing forth the idea that birds 'blackmail' their parents. They scream loudly so as the parent is left with the choice of giving the bird more food, or letting it scream until a predator comes. Now this doesn't really seem to make sense to me. How could one bird decide one day, okay, I am going to scream really loudly until you give me food, or else I will just keep screaming until a fox comes and eats me and you.

Baby Bird: SCREAM SCREAM SCREAM!

Mommy Bird: Here is some food.

Baby Bird: SCREAM SCREAM SCREAM!

Mommy Bird: I already gave you food.

Baby Bird: SCREAM SCREAM SCREAM!
Mommy Bird: Okay here is some more food.

How do you prove that the baby bird is 'blackmailing' the mommy bird? Could he not just be hungry, and want more food? I don't think that birds can go through the process of thinking, 'if I scream, I will attract predators, so if I keep screaming, my mommy will want to shut me up so no predators find us, so if I just keep screaming, she will give me more and more food.'

Um...I don't know, but that just doesn't really seem logical to me that a baby bird would know about predators even before he is out of the nest, and that he would try to threaten his food-provider, who could just up and leave if a predator came.