Early in April last year (2016) I was lucky enough to catch up more than once with a rare Yellow-browed Warbler at my birding “local patch” in north-west London — Brent Reservoir, also known as the Welsh Harp.
The Yellow-brow can be hard to observe, since it is almost constantly in motion, flitting short distances from branch to branch. Luckily it is not shy, and I had close views of it and also heard its distinctive call, a piercing “tsee-WEET”— strikingly loud for one of the smallest Old World warblers.
The Yellow-browed Warbler (Phylloscopus inornatus) breeds across much of northern Asia and normally winters in tropical south-east Asia. But on leaving the breeding sites some young birds take a wrong turn and head west across Europe instead of south to the usual wintering grounds. In Britain the bird is normally seen only in small numbers in autumn, mainly on the east and south coasts of England or on northern Scottish islands.
Most of the birds that reach Britain move on, probably to continue west and drown in the Atlantic, but a few — usually only in single figures — attempt to winter here. One of these rare overwintering birds was found at Brent Reservoir on 23 December 2015. It lingered for a few days, allowing some regular local birders and a number of twitchers to see it. (I missed it because I was away over Christmas.) It obligingly stayed until 1 January 2016 so that New Year’s Day birders could include it on their next year list.
The bird then vanished but, to our surprise, it reappeared (or was it a different bird?) three months later, on 3 April 2016, at another part of the site, where it stayed for a fortnight, showing itself daily. I may be wrong, but so far as I know our spring bird was the first Yellow-brow ever seen in London in April. It was certainly one of only a couple of individuals known to have survived into spring 2016 anywhere in Britain.
According to my bird books, the Yellow-browed Warbler is also known as the Inornate Warbler. Inornate? Have you ever come across this word? I hadn’t, so — as always when confronted by an intriguing word — I turned to the metadictionary website OneLook (www.onelook.com), which searches for words across a range of online dictionaries and encyclopaedias. In this case, OneLook offered just a single reference to “inornate”, in Collins English Dictionary, which gives the definition “simple, or not ornate”.
Now so far as I am concerned, the Yellow-brow does not deserve to be labelled “simple, or not ornate”, since it is a pretty little thing. It has greenish upperparts, whitish underparts and two prominent yellowish-white wing bars. Most strikingly, it has a long yellow supercilium, an eyebrow stripe running from the base of its bill and above its eye and finishing towards the rear of its head. This can be clearly seen in autumn, when the bird is most often encountered in Britain, although by April our bird’s supercilium had become worn and less pronounced.
The Yellow-brow’s closest relative is the equally rare Hume’s Warbler (P humei), which is similar but generally duller (even more “inornate"?). Better-known near relatives found in Britain are three slightly larger birds — the Common Chiffchaff (P collybita), the Willow Warbler (P trochilus) and the Wood Warbler (P sibilatrix). These three are also eligible to be described as “inornate”, since they have shorter and less obvious eye-stripes and they lack wing bars, although they may have yellower tummies than the Yellow-brow.
Our Brent Reservoir superstar was last seen on 17 April 2016. I hope it managed to make its way back to its birthplace and find a mate.