For any gull connoisseurs out there, this dark gull was in the fountain outside Cardiff City Hall this morning. Dave Slade & I concluded that it was just a particularly dark lesser black backed (probably 3rd year summer plumage), but I would be interested to hear any alternative theories or comments on how common this is.
I don’t “do” gulls, but noticed this one because it was so much darker than a nearby herring gull, as you can see in the first two photos.
Glamorgan Bird Club 
I would never confess to being a connoisseur, but looks like one the ‘purple’-stained gulls we see occasionally (possibly they get their staining from TATA – Holi festival for gulls?). Yes definitely a LBBG. What concerns me more is that the gulls aren’t trapped in there – they seem saturated and very low in the water?
Hi Barry, thanks for replying. I wondered if it was just oil, I saw a similarly dark gull posted from Ogmore… I’ve never seen gulls in the fountain before, and these two didn’t seem too happy with their location, and were nervous of flying out because the lip of the fountain was too high for them to see over – but they did both make their escape whilst we were watching. I guess the staining and unusual location would indicate that they weren’t local birds, and didn’t realise that the fountain was a bad spot to land in!