In reply to BusyLizzie:
Lots of warblers are notoriously difficult to tell apart unless you have a really good view of them, even then some don't become easier - especially rarities.
Most of them can be reliably identified by song/calls followed up by visual. Many years ago when I was a teenager and properly into birdwatching I used to have some (but not much) proficiency at this - now - none, except for chiff-chaff/willow-warbler - but that's only because it's the easy one 😁
Of course unless you're into ticking lists, it doesn't really matter, but it is somehow strangely satisfying being able to identify different birds.