The white-headed Long-tailed Tit in Crowborough is unfortunately not a repeat of the Northern Long-tailed Tits Aegithalos caudatus caudatus that occurred in Lewes in the winter of 2003/04. A Northern Long-tailed Tit would show a purer white head, a neater demarcation between the white nape and black mantle and have extensively white tertials. Whilst likely a an aberrant British Long-tailed Tit Aegithalos caudatus rosaceus (I seem to recall a similar presumed aberrant individual in Norfolk being featured in Birding World) intergrades should be considered as Northern Long-tailed Tits interbreed freely with the European Long-tailed Tits Aegithalos caudatus europaeus across a narrow band from Denmark eastwards and such intergrades could potentially occur in Britain. However, Dutch Birding recently featured illustrations of such intergrades, and although I do not have a copy to hand, I seem to recall they still showed more extensive white edgings to the tertials and retained the dark coronal bands to a greater extent than the Crowborough individual.