 The red warbler ( Cardellina ruber ) is a small passerine bird endemic to the highlands of Mexico , north of the Isthmus of Tehuantepec . It is closely related to , and forms a superspecies with , the pink @-@ headed warbler of southern Mexico and Guatemala . There are three subspecies , found in disjunct populations , which differ primarily in the color of their ear patch and in the brightness and tone of their body plumage . The adult is bright red , with a white or gray ear patch , depending on the subspecies ; young birds are pinkish @-@ brown , with a whitish ear patch and two pale wingbars . 
