Taxonomy
A 2010 study of mitochondrial DNA of the spoonbills by Chesser and colleagues found that the Roseate and Yellow-billed Spoonbills were each other's closest relative, and the two were descended from an early offshoot from the ancestors of the other four spoonbill species. They felt the genetic evidence meant it was equally valid to consider all six to be classified within the genus Platalea or alternatively the two placed in the monotypic genera Platibis and Ajaja respectively. However, as the six species were so similar morphologically, keeping them within the one genus made more sense.
Read more about this topic: Roseate Spoonbill