A population of the Galapagos finch Geospiza fortis undergoes directional selection for larger bill size after Geospiza fuliginosa colonizes the same island. This is an example of:

character displacement

Explanation:

Character displacement is an evolutionary change which happens in a scenario whereby two identical species live in same environment. When this occurs, natural selection takes place which then favors a divergence based on the characters that the organisms possess.

Therefore, when a population of the Galapagos finch Geospiza fortis undergoes directional selection for larger bill size after Geospiza fuliginosa colonizes the same island is an example of character displacement.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link:

the scientific method.