In the conifer forest just below the alpine zone of a mountain top, two closely related species of birds that feed on small flying insects have been living together for millions of years. A local naturalist notices that the beak sizes differ on the two birds. The species that eats mosquitoes has a small delicate beak, and the species that eats robber flies (bigger than mosquitoes) has a very large beak. By accident, the naturalist stumbles upon a fossilized bird on the mountain that looks like it could be the ancestor of both species except its beak is neither small nor large, but intermediate in size. What principle could be at work in shaping the beaks of these birds? a. competition b. ecological niche development c. coevolution d. character displacement e. all of the above

Character Displacement this is an evolutionary divergence which usually occurs when two similar species inhabit the same environment. This circumstance occurs where differences among similar species whose circulation in an environment overlap geographically are feature in regions where the species co-occur, but tend to be minimized or lost where the species' circulations do not overlap. Which is same case as that of the birds.