I have taken the liberty to copy your query onto the Upton Warren Worcestershire Forum as I know there are many knowledgable and helpful birders on that site.
I'm sure they will come up with an answer for you
Originally Posted by Theonlymarmot
I've just walked the dogs around the fair sized manmade lake on our housing estate near Stourbridge/Brierley Hill. This is a walk I do every day. I was surprised to see a barnacle goose amongst the resident canada geese. Has anyone a likely idea why it would be there? I'm not at all an experienced birder but I do take notice of what's around, I know it's a barnacle goose and have never seen one there before.