The subspecies of this bird can usually be distinguished by their difference in size and plumage. The subspecies "Phaethon aethereus mesonauta" can be differentiated by its slightly rosy tinge when its plumage is fresh, the bolder look of the black barring on the upper wing, and the more solid look of the black on the outer wing. The subspecies "P. a. indicus" can be distinguished by its smaller size, its smaller mask on the face, which often does not extend far behind the eye, and its more orange bill with a black cutting edge.