Why are some chickens small and some big?

Answer 1

It is fairly common for one individual in a group of young to have inherited a strong sense of survival and competition. Even baby birds in their nests how this tendency. Or . . . it may be that one baby birds learns to get more food after it behaves in a way that gains it more food. Perhaps one time, he accidentally gets in front of the other babies in the nest, and is rewarded with a nice worm. At the next feeding, it might try on purpose to get in front of its nest-mates . . . and a new behavior is started!

Others babies may have inherited a weak sense of competing for food, hence tend to be the 'runts'. So it is with chicks.

Answer 2

Many young pullets lay a few "test" eggs as their reproductive system develops.

Some eggs first laid are yolkless or mis-shaped. It takes a few days for the hen to start producing optimum size eggs typical for her individual breed.

Answer 3

All chickens lay eggs (not chicks), chicks hatch out of eggs if the eggs are fertilised by a cockerel.

In nature all the eggs a chicken would lay are hatched out. However, man has over time domesticated the chicken and we take the eggs that the chicken lays (and keep them away from the cockerels) and eat them, this means that the chicken never 'fills her nest' so she keeps laying eggs.

Answer 4

Different breeds. Just like people, chickens come in all sizes and colors.