Thanks for your thoughts folks. The critical error in the attached definition I was relying on is the one of Britain / Great Britain which wrongly (it seems) defines it only as a single landmass not containing outlying islands that are managed from the mainland. That simple error in definition wrongly created the contradiction in my thinking. It states only the British Isles contains islands like Shetland and Scilly, but Britain doesn’t.
Hope that makes sense.
Www.historic-uk.com/HistoryofBritain/The-UK-Great-Britain-whats-the-Difference/
The link above sometimes breaks but I have copied the text below, but the piece highlighted in red about the definition of Britain is I believe wrong, as it refers to it as only being a single landmass, and NOT including outlying islands - hence my overall point about including birds on Shetlands/Scillies but not NI.
The UK & Great Britain – What’s the Difference?
(by Ben Johnson)
It’s a question we often get asked; The UK, Britain, Great Britain, The British Isles, England… what’s the difference? Well, being the helpful folk that we are, we’ve decided to put forward a helpful cribsheet on just that subject!
The United Kingdom (UK)
The UK is short for The United Kingdom of Great Britain and Northern Ireland… quite a mouthful! It is a sovereign state (in the same way as France or the USA) but is made up of four countries; England, Scotland, Wales and Northern Ireland. For Americans, the best analogy would be that the UK is like the USA, whilst its four consistent countries are like states.
There is a long and complicated history that follows the formation of the United Kingdom, but here are the highlights:
c. 925 – The Kingdom of England. Established by the unification of Anglo-Saxon tribes across modern day England.
1536 – Kingdom of England and Wales. A bill enacted by King Henry VIII which effectively made England and Wales the same country, governed by the same laws.
1707 – Kingdom of Great Britain. The Kingdom of England (which includes Wales) joined with the Kingdom of Scotland to form The Kingdom of Great Britain.
1801 – United Kingdom of Great Britain and Ireland. Ireland joins the union, and once again the name changes.
1922 – United Kingdom of Great Britain and Northern Ireland. The Republic of Ireland (Eire, or ‘Southern Ireland’) withdraws from the union, leaving just the northern counties of Ireland. This is the UK that remains to this day.
So when was the UK established? Although some people argue that the UK was formed in 1707 by the Act of Union between England, Wales and Scotland, the name United Kingdom wasn’t adopted until 1801 when Ireland was brought into the union.
Great Britain (sometimes just referred to as ‘Britain’)
Great Britain is not a country; it’s a landmass. It is known as ‘Great’ because it is the largest island in the British Isles, and houses the countries of England, Scotland and Wales within its shores.
The name Britain derives from the Roman word Britannia, but there are two conflicting arguments about why the ‘Great’ was stuck on the front of it. The first is that it is used to distinguish Britain from its similar sounding, but much smaller French neighbour, Brittany. The second reason is due to the ego of a certain King James I, who wanted to make it abundantly clear that he wasn’t just the king of the old Roman Britain (which only included England and some of Wales), but of the entire island; thus he referred to himself as King of Great Britain.
The British Isles
The British Isles is the name of a group of islands situated off the north western corner of mainland Europe. It is made up of Great Britain, Ireland, The Isle of Man, The Isles of Scilly, The Channel Islands (including Guernsey, Jersey, Sark and Alderney), as well as over 6,000 other smaller islands.