The seven species of New World vultures and the 15 species of Old World vultures represent two separate branches of avian evolution that have converged to form ecologically and morphologically similar birds. The Old World vultures are related to hawks and eagles (Family Accipitridae) while the closest relatives to the New World vultures are storks. Sibley and Monroe (1990) place both the New World vultures and storks in the Family Ciconiidae. It is interesting to note that the proponents of DNA hybridization systematics have lumped into one order (Ciconiiformes) such traditionally diverse groups as shorebirds, gulls, and alcids; hawks, eagles, and vultures; herons, bitterns, egrets, storks, spoonbills, and flamingos; shearwaters, petrels, and albatrosses; pelicans and cormorants; loons; and penguins.