I mentioned Darwin. The Juncos have a large variety of plumage that is specific geographically. We know the Oregon variety is the dominant of all the others. Each of the others has some degree of the characteristic of the majority population.

The difference between the varieties are the trees where they nest and the food they consume.

The Oregon variety enjoys the temperate forest on the west coast which have a higher density of pines than the east coast. When a forest is temperate it supports more varieties of seeds and live food. The east coast has pines, in the case of New York state, it is the White Pine. 

The Oregon species has a hearty environment to nest and live. The New York species of "Slate Colored" Dark Eyed Junco has fewer pines trees, hence, fewer types of seeds and live food.

What occurred with these varieties is that they all started out like the Oregon species, but, were unable to survive among changing lands, trees and food sources, so each species adapted with their inherent genetic content. With each new plumage came a territory. That territory has a finite amount of calories for each bird that lives within that ecosystem. 

The available calories encouraged a robust plumage with an abundance of food while the palest color CHOSE to limit the number of calories available to the young as they were conceived and hatched. That CHOICE occurred because of the genetic basis for it's calorie use. It is not to say one species is heartier or healthier than another. It simply means as the calories available to a migrating species were realized, the genetic basis of the animals CHOSE it's best outcome. It was not a cognitive choice, it was a genetic choice.

I will continue to discuss the Slate Colored Dark Eyed Junco next week and it's habitat in New York State that supplies it's nesting environment and it's food source.

There are other indicator species, both plant and animal. I believe in examining this bird it will open up a greater understanding of the others.