Siberian Vagrants: The Yellow-browed Warbler

Gelbbrauen-LaubsängerSoft evocative calls in tall herb. Every year there is a pronounced migration of Goldcrest (Regulus regulus). But it is worth to risk a closer look. In the mixed flocks sometimes there are representatives of small Phylloscopus-Warblers. One of them, the Yellow-browed Warbler (Phylloscopus inornatus), comes from the forests of the taiga between Sea of Okhotsk and Ural. This bird is oftern named Inornate Warbler, too.

The Yellow-browed Warbler is a small warbler with a fine, pointed beak and relatively short tail. In appearance this Phylloscopus-Warbler resembles a kinglet. You might misidentify him for a Firecrest (Regulus ignicapilla). In comparison it is much more delicate than the common native Phylloscopus-Warbler, the Chiffchaff (Phylloscopus collybita). The Yellow-browed Warbler is eight millimeters shorter.

Especially in this year many Yellow-browed Warbler seem pursue a southwestern route across Europe. In Finland, some 1,000 Yellow-browed Warblers were observed since the beginning of September. In recent years there were usually throughout the fall less than 300 individuals. On the way to the southwest at least some of these birds should fly over central Europe.

Most observations succeed between mid-September and mid-October, mostly in the coastal regions. Already unusually early, in late August2015, the first fall observation was detected. This was followed by observations mainly on Heligoland and along the North Sea coast. The observations from the inland areas are much rarer. But inland observations speed up in the time comparison over the recent years. Thus a Yellow-browed Warbler (Phylloscopus inornatus) was discovered in autumn 2001, north of Worms (roughly 100km south of Frankfurt/ Main) at a birdnet for ringing on 30.09.2001.

In general, the maximum numbers are reached in early October. So now is the right time to look for the rare but regular visitor.

To which destination Yellow-browed Warbler you observe in Central Europe move on is largely unknown. However, the already long journey from Siberia seems to go further on to the southwest. In fall 2013, a bird was ringed on Helgoland. This bird was photographed in January 2014, on the Canary island of Lanzarote. Yellow-browed Warbler are regular vagrants in autumn in Europe, although the main wintering areas are in the subtropics and tropics of Asia.

The reasons for the annual appearance of hundreds of Yellow-browed Warbler in Europe have not yet been finally resolved. One explanation are weather conditions, heavy storms over Russia. If weather conditions were the cause of vagrants, smaller birds would have been blown more often than larger ones. But statistical analysis did not reveal any association between the frequency of vagrants and their body size. In addition, the Yellow-browed Warbler occurs far too regularly in Europe, as unusual weather conditions during migration can be held responsible. According to the researchers vagrants might land in the wrong wintering area rather by an error in the execution of their innate, genetic migratory program. Thus, the origin would be in a determined, persistent misorientation of birds.

Yellow-browed warbler can actually appear anywhere on passage. In riparian, lowland forests, forest edges, shrubs and bushes on the beach, in recreational parks or in gardens.

Ornithologists should be familiar mainly with the characteristic and often recited call (www.xeno-canto.org/species/Phylloscopus-inornatus). This is a excellent sign, to get awareness of the birds. Straightaway this small warbler resemble in appearance the Firecrest. They differ from the species of the genus Regulus immediately by the eponymous green-yellow supercilium. This supercilium extends quite far backwards and is bounded below by a black eye stripe. The head is olive green with a lighter rump and upper tail-coverts. Two distinct, but with varying intensity pronounced wing-bars, which are caused by the pale edges of primaries, are usually the most prominent feature. The top of the head is dark green with a very weak indication of a stripe.

Yellow-browed Warbler differs from its congener Pallas’s Leaf-Warbler (Phylloscopus proregulus) – occurring later as a vagrant – especially by the lack of flashy yellow rump. In contrast Pallas’s Leaf-Warbler show a pronounced (yellow) apex strip is not as on the head by far.

As an exceptional rare vagrant Pallas’s Leaf-Warbler, can be seen from time to time in Middle Europae. The Yellow-browed Warbler overlaps in its distribution in the breeding area with the Hume’s Warbler (Phylloscopus humei), who also appears as a stray now and then in Germany.

To cope with the growing demand for top shots of the rarer species of the Palearctic Bird-Lens.com is keen to enrich the range of pictures of birds you can find in the western palearctic. Trips to productive locations in Germany but also to remote places in the world to capture images of rare birds of western palearctic were very successful. The nice image of the blog was shot during a trip to Happy Island, near the small town of Qinhuangdao (Magic Woods) near an island in the Yellow Sea of China. The image is only a first impression, what you will find in the gallery for Happy Island birds and in the “Picture Shop” very soon. Just give a message, if bird-lens.com could serve you with an image needed before the new pictures are online.

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