Final answer:
Natural selection is expected to produce the largest evolutionary change in a population of birds, as it actively selects for traits that increase an organism's survival and reproductive success.
Step-by-step explanation:
The question concerns which factor would be expected to produce the largest evolutionary change in a population of birds over a given period of time. Out of the options provided, natural selection is expected to produce the greatest evolutionary change. This is because natural selection acts on phenotypic variations that are beneficial for the organism's survival and reproduction within a particular environment. Mutations introduce new genetic variations, which are raw materials for natural selection, but by themselves often have little immediate impact on the population. Conversely, the Hardy-Weinberg equilibrium describes a theoretical non-evolving population where allele frequencies remain constant. Factors such as genetic drift, gene flow (or migration), and random mating can affect allele frequencies, but their effects are typically smaller compared to those of natural selection, especially in larger populations or over longer periods of time.