At this time of the year birds are on the move for winter, so yours could have moved further south.
I'm just outside of Sheffield and like you I normally have plenty of Blackbirds in my garden but at the minute I'm down to a couple.
A lot of people think they are seeing the same birds all year round but a lot will be migrants from further north and even from abroad.
My Flickr photos
In reply to Alan.:
Nary a one for me & I'm pretty far South!
2013 photos & vids here
eff37 on Flickr
In reply to WendyBartter:
Same here on Anglesey, very unusual for me not to get even one in the garden for at least two months now.
Lot to learn
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