The lower bird is smaller and dumpier with smaller, rounded head, greyer central crown stripe, two very broad white wing bars and, yes, lacks yellow on the undertail coverts.
英
美
- 下面那只鸟体型较小和粗短,并有较小而浑圆的头,较灰色的头央线,两条很宽的白色翼带,以及不带黄色的尾下覆羽。(冠纹柳莺特徵)