I have had this niger seed bird-feeder for some time but it didn't work in the garden in Hemel Hempstead because we hardly ever saw any goldfinches. Here in France, however, there are regular visits from goldfinches as long as the sunflower kernel feeder is stocked! 
So I thought I'd have another go with the niger seed feeder. But it's always made me wonder if the really small holes in the plastic tube are TOO small - I've provided some photos for reference below - what do you think?

And a close up of one of the holes with a tape measure in mm for reference:

So I thought I'd have another go with the niger seed feeder. But it's always made me wonder if the really small holes in the plastic tube are TOO small - I've provided some photos for reference below - what do you think?
And a close up of one of the holes with a tape measure in mm for reference:
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