They, along with Stewart and Stringer's comments have had me thinking about how it's almost impossible to keep abreast of everything when it comes to ID even for UK species. Both experienced birders, one lapsed and one current ringer and certainly with more experience of birds in the hand and bigger lists than me yet neither aware of Shirihai's text on Iris colour in relation to ageing Blackcap. Then again the only reason I had just read it was that Blackcap's have been often the only migrants I have seen on certain days this year and I dug the book out to check if there were any obscure races that I should perhaps be more aware of to add a bit of excitement and challenge to the "oh it's another Blackcap" moments.
Frankly if you started asking me about any of the other species/races accounts in the genus I'd seriously struggle hence the halitosis joke a few days ago in reference to halimodendri Lesser Whitethroat. So how do you keep up? For me I accept I can't possibly know as much as I'd like, I rely on remembering the species I'm familiar with. I find that once I've 'added' a new bird and spent a little time with it I feel more comfortable with ID in the future, although this has a 'Use By' (or lose by) date with me. I try and reinforce this by selective 'habitat' based reading so If I'm expecting a few weeks seawatching I'll go and re-read some of the key species or the ones that might just turn up, I've now lost count of the number of times I've re-read Little Shearwater without it ever been useful. Any of those Bullfinch today could have been 'northern' types, as the timing would be consistent with past invasions and I wouldn't have known as it's just not a race that has come across my radar in the past and therefore I've never seen or read anything about the ID. Anyone wishing to impart alternate strategies for dealing with information overload should head for the comments.
The most interesting sighting of the day was a dragonfly, four days into November, my first November dragon, which I think is a Common Hawker and I know was responsible for making me re-start counting Gadwall four times (there were 49)trying to get a half decent image of it as it shot around the reeds to the west of the hide at Linton.