Hmm… I probably missed it, but why are there so many colorful birds in the tropics? It just says that they probably came from outside the tropics, but not why there are so many.
While this new study sheds light on how iridescence spread through the bird family tree over the course of millions of years, some big questions remain. “We still don’t know why iridescence evolved in the first place,” says Eliason.
Now that, is something I’d like to know too. My guess: to hide from predators.
Prey adapted to blending in to hide from predators. The majority of colors in the tropics are green (leaves), brown (earth, trees), yellow (sunlight?), and blue (sky).
For prey on the ground, the color of the ground, shrubs, etc. is probably green and brown. For prey higher up, if the predator is on the ground, probably blue, green, and brown are good colors to hide. Maybe predators of birds also have adapted to see other colors than the iridescent colors birds have.Again, a guess, but maybe we’ll know someday.