Niger seed (nyjer seed or thistle seed) is known to be a favourite of finches, due to the shape and structure their beaks, which are suitable for a smaller type of bird seed.
“Great product. at a good price. Over time this has attracted a lot of birds - goldfinches ( of course) but also siskins, greenfinches , chaffinches . In fact other finches too as well as woodpigeon when the other feeders are dry. There is a lot of leakage onto the ground which can’t be avoided really and does allow more birds to feed at one time.”
“Excellent quality Niger seed from Vine House Farm. The seed is very fresh, clean and shiny and the goldfinches love it. There's far less waste than with seed I've had from other suppliers. Will buy again.”