ML647003102

觀察細節

Return of the buff-bellied junco after a two week absence. Note the cloacal feathers are white and the undertail coverts are a yellowish buff. I would guess that if the feathers were stained, the undertail coverts and buff belly would be the same color rather than different. Rarely individuals have yellowish buff undertail coverts but with white bellies- https://macaulaylibrary.org/asset/646963711 This bird could be a buffy-undertailed individual that also got stained, but the staining did not affect the undertail coverts and cloacal feathering, or the undertail coverts and cloacal feathers molted after the belly staining. Alternatively, this bird possesses some mutation that has affected the pheaomelanin in the belly and undertail coverts, but not the cloacal area. As far as I can tell, the underside of the tail is stark white and unaffected by the pigment anomaly, or it molted after the staining event.