This document discusses different types of evolution in birds. It defines evolution as changes in species over generations through natural selection. There are several types of evolution described: retrogressive evolution where complex organisms become simpler; microevolution involving small changes within species; macroevolution resulting from microevolution over many generations including speciation; divergent evolution where related species evolve different traits; convergent evolution where unrelated species independently evolve similar traits adapted to their environment; and parallel evolution where species acquire similar characteristics evolving together in the same space and time.