(troglodytes troglodytes)
The Wren is probably the most common bird in Scotland with an estimate of up to 8 Million birds being present in winter when the population is swelled by Scandinavian migrants. Four subspecies are recognised - the Shetland Wren, the Fair Isle Wren, the Hebridean Wren and the St Kilda Wren each being endemic to their local geographic area. The physical differences of these subspecies are rather subtle but in general they are very slightly larger, darker and have longer bills and legs than the mainland birds. The song of these subspecies also appears to be very slightly different.