These sorts of studies can help researchers determine the relative importance of nurture and nature in determining a trait. Nature here would refer to genetics passed down to an individual from its parents, whereas nurture refers to the environment the individual is exposed to.
Answer: A
Explanation: There is no need to conduct and experiment if you already know the answer
In this question, there are no options given to choose from. So i would answer this question based on my knowledge. The most likely cause of the observed variation is adaptation and evolution. The birds of that island adapted to the food source and then they evolved as per the requirement of the place and food source.