I is for Icterine Warbler

Icterine warbler (Hippolais icterina).

The icterine warbler only just about classifies as a British Bird, but there is a severe shortage of natives beginning with ‘I’. It is a passage visitor (stops off on migration) and scarce migrant breeder in Britain.  It is usually found on the mainland in Western, Central and Northern Europe, all the way up to subarctic Russia. It is therefore surprising that Icterine warblers do not breed on our temperate isles more regularly. Perhaps crossing the waters of  the channel and the North Sea are just a little too much of a stretch on their exhausting  migration.  Although like many of our migrants the icterine warbler winters in sub-saharan Africa, it is excluded from the Mediterranean by its close and similar relative, the Melodious warbler (Hippolais polyglotta), which is also an occasional visitor to Britain.

Icterine warblers look as if they have been completely washed with yellow, including their greyish-green back.  The clue is in the name, as The name icterine means “yellowish’. This distinguishes them from our more common phylloscopid or leaf warblers, the Chiffchaff (Phylloscopus collybita), Willow  warbler (P. trochilus)and Wood warbler (P.sibilatrix), which are more greeny brown and only partly yellowed.
But icterine warblers don’t just have pretty looks, they also have a great voice. Their long, loud,  babbling, eclectic and almost electric song seems to carry on forever. To add to the song’s complexity, it sometimes also incorporates mimicry of other bird calls.

Otherwise, ‘Ickies’* have rather typical warbler habits. They are shy and spend their time skulking in vegetation, usually only  given away by their voice. They forage amongst the leaves for insects and summer berries.

Icterine warblers settle in habitats with dense hideaways such as woodlands, scrub and the edges of forestry plantations, preferably in river valleys.  They have only been confirmed breeding five times in Britain, all of which were in the Scottish Highlands. The first record was in 1992 and the latest in 2009, when two pairs bred. The young successfully fledged from at least two of these attempts, including four young raised in Orkney in 2002¹.

They use Britain more regularly as a hotel than as a nursery. An average of 137 drop in per year making them one of our most common rarities ². Such visits often occur as crowds of birds rather than the occasional lost soul, and bigger crowds are thought to be related to breeding years . In the summer of 2009, 50 individuals were reported whereas a record 175 appeared in the first breeding year.

The detection of British breeding icterine warblers is thought to be a testament to the efforts of modern bird recording schemes. Britain is one of the great birdwatching nations, and the recent attempts to survey every square kilometre of the islands , in ‘tetrads’ mean even our wilderness areas miles from the nearest bird hide do not go unchecked. Thus the activity of such elusive birds gets noticed, and protective measures can be put in place.

It is interesting to think of this attractive visitor becoming more common in Britain. Perhaps it might follow the example of the Collared dove (Streptopelia decaocto), once a rarity from the mainland that had birdwatchers flocking, and now a staple garden bird. Only time will tell.

*I didn’t make it up. This is a common term used by birdwatchers.

References

1- Alan Tilmouth. (2009) BTO Atlas work produces Icky results. Available from: http://www.birdguides.com/webzine/article.asp?a=1764

2- Robert A Robinson. (2013)Profiles of birds occurring in Britain and Ireland-Icterine warbler Hippolais icterina   [Vieillot, 1817]. Available from:  http://blx1.bto.org/birdfacts/results/bob12590.htm