The willow warbler (Phylloscopus trochilus) is common and widespread, breeding throughout northern and temperate Europe and Asia, from Ireland east to eastern Siberia. It is, however, strongly migratory and almost the whole population winters in Sub-Saharan Africa. It is greenish brown above and off-white to yellowish below; the wings are plain greenish-brown with no wingbars. Aside from its pale legs it looks almost identical to the chiffchaff (Phylloscopus collybita). However, if you think you’ve seen a willow warbler but it’s making an almost metronomically regular t’ss, t’ss, t’ss, t’ss… sound and has dark legs it’s a chiffchaff, the warbler has a much more warbling, melodious song. Here’s a recent photo and a snippet of his song that I recorded in late April 2017 in Rampton Spinney, South Cambs.