When something 'big' turns up, if you want to see it, 90% of the time you can. Eastern Crowned Warbler, Citril Finch, Purple Martin, if you had the time, money and inclination, and didn't sit on your hands for 48 hours weighing up whether to go for it or not, then it would be on your list. Most serious listers have all three (and then a few more). Most of the 'part-time' listers of the UK mainland might not island-hop, but will still take a long drive to Flamborough or Nanquidno to knock-off that missing warbler, pipit or yankee warbler. This means that we have a large pool of birders with almost identical lists (most will be missing at least one mega that arrived when they were on holiday abroad - and 550 ticks in Uganda still don't make up for that Long-tailed Shrike). We do now have a number of extreme seabird records that have meant major gaps appearing in the listers list (Tufted Puffin anyone?)
As for me, I have plenty missing from my UK list. A veritable bonanza of 'missing in action' species, most obviously Green-winged Teal, Lesser Scaup,Snowy Owl, Red-throated Pipit, Thrush Nightingale... I could go on.
But. These aren't the real gaps. Those species that are assumed to be on your list, but have somehow evaded you for more years than you care to own up to. Today I launch my latest list - the list that all birders can be judged by - 'The commonest species not on your list, list'. It's more fun to know what others are missing rather than what they've seen. Just as bad news is more captivating than good news, the fact that a UK500 lister might still 'need' Capercaillie is much more interesting than their complete set of UK larks and pipits.
So, my four most laughable blanks are:
Capercaillie (looked, dipped, haven't even heard one), Corncrake (not visited any breeding areas and haven't flushed a migrant), Cory's Shearwater and Great Shearwater (hundreds of hours spent seawatching, but 99% of it in Kent). There, I'm outed. It didn't hurt and it's strangely cathartic. Go on, give it a try...