It seems Common Redpolls are like buses then... Thought this might be a good opportunity to clarify a few things, just in case this turns out to be a good year for these beasts.
Redpoll taxonomy has always been complicated and they've been through a number of splits and lumps. However, currently three species occur in this country: Lesser, Common and Arctic. Arctics are by far the rarest, very white and sometimes separated into two forms: Coues's Redpoll (C. h. exilipes) from northern Europe and Hornemann's Redpoll (C. h. hornemanni) from Greenland and Canada. However, for the moment we can forget these.
So we're dealing really with two forms around here: Lesser Redpoll (Carduelis cabaret) which is the form breeding in the UK and adjacent parts of Europe:
...and Common Redpoll (Carduelis flammea) from northern Europe which sometimes reach the UK as winter visitors.Common Redpolls were once known as 'Mealy Redpolls' when they were still lumped with Lessers a few years ago.
As you can see, both are very variable and there is quite a bit of overlap. Common Redpolls of the races 'rostrata' (from Greenland etc) and 'islandica' (Iceland) may also reach us from time to time, but let's not worry about those either for the moment.
So the most important issue for us is making sure we can separate Lesser Redpolls from Common Redpolls. As Mick found, when caught with Lessers, they do sometimes stick out. However, as Jim found, there is a lot of overlap and sometimes they can be tricky. So what should we look for? Well, in a nutshell, Common is a paler bird with longer wings and tail, whereas Lesser is a browner bird with shorter wings and tail. However, to break it down a bit more, try looking for:
1. head of Common often looks a bit greyer than uperparts
2. on underparts, Lesser has buff breast and flanks contrasting with white centre, Common has more uniformly pale ground colour
3. primary projection (comparing exposed primary tips with exposed tertials) is usually 100% or more in Common, and 100% or less in Lesser, though there is a bit of overlap
4. rump is buff, brown and streaky in Lesser and much paler with sometimes even a small white area in Common
5. Common generally has white wingbars, Lesser more buffy
6. in Common the undertail coverts are white and sometimes heavily streaked, in Lesser, they are less streaked and usually buffy
7. if you look in Svensson, you'll see that one or two measurements help - although there is overlap here too
Lastly, here are a few more pictures Mick P took of his birds which are useful for reference.