Why do some species of birds-of-paradise have such eye-catching plumage?
Around New Guinea, there's a watery hill almost two hundred and fifty feet high. This isn't a hill on the ocean floor, but a hill on the ocean's surface.
The answer is diet. Those species with the most elaborate plumage also have the most diverse and reliable diet: a variety of insects, and fruits rich in complex nutrients. With this reliable food supply, females can raise the hatchlings without help from the males.