Birds are the most diverse creatures on Earth. Not only have they changed into different species on large continents, they have also adapted specifically to environments on islands.
A new classification system is in the form of a circle with increasing diversity as one moves out in time from the center. different types of birds are correctly located on the figure covering a period of 50 million years.
There is not one specific ancestor. "Base" species take the form of a circle of time moving out from the center and new kinds of birds branch off directly to the outer edge. Fast evolving birds are in red; slower ones are drawn in blue.
Significantly birds such as woodpeckers often split into new species, while hornbills, for example, did not. There was more diversification in the Western Hemisphere. Furthermore, species did not proliferate in the tropics because the climate remained stable there over a long period.