A small bird, common in Europe and Asia, with a long tail that it moves up and down all the time as it walks along the ground. That constant tail movement is where the name comes from, and it is the easiest way to recognise the bird — it does not hop like a sparrow, it walks and trots, and the tail bobs with every step. There are several kinds: white wagtails, grey wagtails, yellow wagtails. This matters for Taiwanese students because you have almost certainly seen one without knowing the English name — the white wagtail 白鶺鴒 is everywhere in Taiwan in winter, walking around riverbanks, car parks and school playgrounds, and enormous flocks roost in city trees. So this is not an exotic foreign word for you; it is the bird outside your window. It is a countable noun: one wagtail, two wagtails. Written as one word, no hyphen.

鶺鴒（台灣冬天到處可見的白鶺鴒就是 white wagtail）。名字來自牠走路時尾巴不停上下擺動。