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.
“I got the niger seed following a viewing of goldfinches on the bird feeders, to encourage them to stay. I had heard it was their favourite seed. However, my goldfinches are very happy with dehusked sunflower bits and have yet to sample the niger seed in large quantities. They don't know what they are missing.”
“The birds can’t get enough of them. They arrived on time and were well packed.
Would highly recommend to those wishing to see finches on their feeders”