many birds can’t eat sunflower seeds, they can’t break through the husks. Sparrows will ignore them, but if you put out already-shelled sunflower seeds they will enjoy them.

Nor are all sunflower seeds the same. The striped sunflower seeds are thicker-shelled and lower in nutrition than black sunflower seeds, so birds have to work harder for less reward if you put them out. It’s worth getting seed from a reliable source like the RSPB in the UK, or the LPO in France. Elsewhere, it’s worth looking up your national bird-protection society, to see what they have to offer.