Geographical Isolation is the mechanism that might have led to the appearance of the Hawaiian honeycreeper.
Geographical Isolation is the term used that refers to a population of animals, plants, or other organisms that are separated and unable to exchange genetic materials with other organism of the same species.
Geographical Isolation may be a result of coincidence or accident.
Here are some factors of Geographical Isolation:
1) Isolation by barriers
2) Isolation by distance
3) Isolation after an Event
4) Isolation by separation