I think a lot of the blackish colour on the nail is lost in light glinting off the bill. I've taken the liberty of farting around with the originals (decreased brightness and increased contrast, hope Adrian doesn't mind) and I don't know about you but I can see a grey smudge in the appropriate place.
Last Lifer - (2312) Dusky Thrush.
Last UK - (453) Dusky Thrush.
Last Garden - (93) Garden Warbler.