Warbling White-eye

Cf. Swinhoe’s White-eye.  Warbling and Swinhoe’s White-eyes together comprise about twenty similar-looking populations which have been classified variously under the formerly recognized species Japanese, Oriental, and Mountain White-eyes.  The current classification is based largely on genetic analyses, and the races are identifiable mainly by location and voice.  The northern populations of both species are migratory and their ranges approach closely enough that they likely occur together at least occasionally—especially in Taiwan, coastal China, and Korea.

The vocal differences between them seem consistent: Warbling has a harsher voice and choppier, chattery phrasing, whereas Swinhoe’s has a thinner, sweeter voice, and smoother, more relaxed delivery. 

They also differ in appearance to some extent, but subtly and with significant overlap.  Overall, the migratory populations now classified as Swinhoe’s (i.e., “Chinese”) are paler and more vividly colored than those classified as Warbling (i.e., “Japanese”).  This distinction does not apply to the resident populations of the Philippines and Indonesia (i.e., “Williamson’s”, “Enggano”, and “Mountain”), which vary and seem to overlap widely in coloration.

“Chinese” (Swinhoe’s) tends to have yellow-olive upperparts and some yellow on the face that usually extends to the forehead, whereas “Japanese” (Warbling) has greenish-olive upperparts and yellow limited to the throat.  Both “Chinese” and “Japanese” typically show a crisp boundary between the yellow throat and gray chest, but both sometimes have yellow that extends farther down onto the chest.  The gray tones of the breast and also differ, at least on average, as “Japanese” often appears medium-gray or slightly brownish, whereas “Chinese” usually appears whitish-gray.  (Note that both often show a faint yellowish wash on their gray underparts.)