Hi mrchumble, lovely photo and yes, it is a male Siskin; pretty little birds and members of the finch family.
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Regards, Hazel
Thank you Hazy, much appreciated.
You're very welcome, we've had a flock of 20 Siskins in our garden recently although around a dozen at the moment, they are such colourful finches and a delight to see. They love sunflower hearts as you have seen; you may just need to dismantle your feeder now its near empty to get rid of the build up of green at the bottom of the feeder as it can carry harmful bacteria; finches are messy little eaters so I have to dismantle our feeders every two weeks to clean them out .... one part bleach to nine parts of hot water and then rinse thoroughly and air dry. Well done on getting such lovely bird visitors and hope the Siskins stay around for a while longer.