Which evidence of evolution is related to Darwin's finches :

On the Galapagos Islands, Darwin observed many species of finches, each on particular islands and with beaks adapted to different foods (seed eating, insect eating and so on).
They all evolved from a common ancestor from the South American mainland, by adaptive radiation into different habitats on the isolated islands.
This geographical distribution of related species is evidence from biogeography.
So Darwin's finches are related to evidences from biogeographical distribution.