Considerably less than annual in occurance, Tony Marr found a flock of 11 Tree Sparrows in a neighbours garden at Port of Ness today. Rarer in local terms in the past decade than Gyr! I saw a bird at Swainbost in c.2005 and one a few years ago on Vatersay south of Barra. They are not common!
Tree Sparrows do occur as migrants from time to time in Orkney and Shetland, and they have had a few this spring. With east winds speculation must be that they are far flung vagrants rather than just wanderers from mainland blighty.