Nick, I am always a great believer in people see what they say they have seen - but no-where in your posts do you actually say whether your garden is in the SOS recording area.
Where is your garden - I see from your website that your photographic studio is in the Avon bird recording area. A record of 2 Serins feeding together in a garden in this country in the winter is rare enough to merit formal documenting in a county record, so it would be interesting to see whether your record, with supporting documentation, needs to be submitted to the Avon bird recorder or the SOS one. For the SOS, Serin is a full description species as detailed by the SOS Rarities Committee.
And Serin is just as much a description species in Avon!
Yellow-fronted canary is a confusion species.
Thank you Ash, unfortunately the garden is about a mile north of the SOS recording area (WNW of the A38), so just in Avon.
The birds appeared in the mornings for a week or so and surprised me by being less timid than Chaffinches / Greenfinches. Quite content to feed together on the small seeds, but not with other birds.
This evening I put three pictures in front of 'the Boy' - Yellow Hammer, Siskin and European Serin as a cross-check. He immediately identified the Serin.
Rich, correct, it is a confusion species, but the ring around the eye on the Serin is too distinct, especially at close distance
Have a look at
and scroll down to 1st march for what Serin looks like at this time of year.