Answer: stabilizing selection acting on clutch size
Explanation:
Stabilizing selection is a form of natural selection in which a particular non-extreme trait value stabilizes the population mean.
However, stabilizing selection also have influence on birds clutch size (i.e. the number of eggs laid by a female bird). This is because the female bird is required to lay many eggs in order to have increase number offspring. However, the number of eggs they laid is directly proportional to the degree of support they can render with their own resources.
Therefore, the female starlings typically lays a moderate amount of eggs in order to stabilize the number of offspring they can take care and hence, increasing their offsprings survival rate.
