This little Siberian beauty turned up very unexpectedly at Portesham last week.
Pallas's warblers are found all across central and northern Asia, but do not breed anywhere in Europe.
And yet they are frequently seen in the UK in autumn (the Portesham bird has presumably been there all winter).
Their normal wintering grounds are in south east Asia, so what are they doing here?
I don't think anyone really knows but I can think of 3 possible explanations:
1) There is an undiscovered breeding area closer to us, which is where our birds come from
2) There is an undiscovered wintering area closer to us, which is where our birds are going to
3) Our birds have made a drastic error in migration, taking them thousands of miles off their intended migration route.
Option 3 is the most generally accepted one, and indeed is the assumed explanation for all of the vagrant birds that show up in unexpected places during the migration season. For a species that breeds in high latitudes, such as northern Asia, a 180 degree error where they fly north instead of south would result in them flying over the arctic to the opposite side of the planet. So an Asian bird would end up in western Europe, a remarkable feat but no further in distance than flying to their normal wintering grounds.