Answer: The theory of natural selection suggests that some members of the population of species have better advantage of others for survival in terms of better phenotypic traits.
Explanation:
According to the given situation, the moths which have color that remain undetected by me as bird has a phenotypic advantage. As I may not be able to observe them on tree trunk or bark or on leaves I can eat only those moths that can be seen through my eyes. I can capture them easily. Such moths which can change their colors in accordance with the color of the tree can camouflage me easily and I cannot observe them and consume them. This promotes their survival over those detectable moths.