How does natural selection work regarding individuals and populations regarding which will be most successful?

Natural selection doesn't really choose what animal/species is going to survive it's all based on the environment they live in. While a blue bird does well in the jungle it may not do well in the desert. For individuals it's based on their genes and genetics. Some are more prone to have a trail that doesn't benefit them and in fact, harms them in their environment. For populations you will see lots of the same animals but with different traits so some may do better in the wild than others because of those traits. A population is more likely to be successful because you do better when working with others. So animals have a better chance to survive if there is more diversity.