Answer:
This would have been an example of the founder effect and the genetic drift.
Explanation:
The founder effect would come into effect because in this scenario, the original population would have already been different because a small number of individuals would be establishing this new population and this would have used a less diverse gene pool. Genetic drift would come into play as this small number of finches would constitute a random selection sample from the larger original population and thus the population would have a less varied gene pool to work with in terms of further evolution. This would constitute a change in the frequency of existing genes and genetic drift would take place.
