In a population of doves in a forest, a small group of long-tailed doves migrates to another forest. over successive generations, the population in the new habitat shows more of the long-tailed doves than the short-tailed ones. which factor could be responsible for this microevolution? stabilizing selection founder effect gene mutation bottleneck effect

The bottleneck effect occurs when the majority of a population is destroyed due to natural disasters or human activity's. This reduces the size of the gene pool resulting in smaller variations from bird to bird. Gene mutation is the permanent change in the DNA or gene. Stabilizing selection occurs when genetic diversity decreases and the majority of the population stabilizes on a specific trait. The Founder effect occurs due to a smaller population leaving a larger population. This leaves the smaller population with smaller genetic variations. The correct answer is the Founder effect. 

This is giving me a headache i have asked others and they don’t know it either