How many chickens does it take to make a chicken baby?

One hen and one rooster; both are chickens. Two.

That depends on what math you are using.

Bookworm has one correct answer.

But if you go by averages ... since a single rooster can impregnate multiple hens ... the answer would be 1 + a fraction.
IE: 1 rooster to 10 hens would result in an answer of: it takes 1.1 chickens to make a chicken baby.

Is this a trick question :P