Professor Dave Explains on MSN

We've already lost around 130 bird species - now more than 1,200 species are threatened

Birds have evolved into more than 10,000 living species, ranging from enormous flightless ostriches to predators capable of ...
insider.si.edu

Bird species : how they arise, modify and vanish / Dieter Thomas Tietze, editor

Introduction: Studying birds in time and space / Dieter Thomas Tietze -- Integrative taxonomy of birds : the nature and delimitation of species / George Sangster -- Studying speciation : genomic ...