Closely related species of birds are also chromosomally similar.
Males transmit signals in courtship through behavioral displays.
Evidence of epistasis from hybridization studies is more scarce.
Plumage features constitute a major component of courtship signals.
Thus mating of females was strictly along the lines of paternal song.
Species can be recognized by their morphological characteristics and songs.
The process of speciation is completed with the cessation of genetic exchange.
Islands are known to differ in the food supply available to ground finches, mainly seeds.
The theory of founder effects does not explain how novel features like plumage traits arise.
Exchange of breeding individuals between two populations tends to homogenize their gene pools.