Niger seed oils

Hi everyone,

Just a quick question about niger seed. I was lucky to have many goldfinches over summer, parents bringing juveniles, and they were clearing my smaller bags of niger rapidly. I bought a large sack of niger seed and they got through most of it over the last 3 to 4 months. I'm currently seeing less goldfinches, but the odd one still turns up but they're less bothered with the niger feeder. I'd read somewhere that once opened, niger seed can lose its natural oils, dry out, and then birds ignore it. Has anyone observed similar? Just wondering if i should start on a new bag of unopened seed if what is left of the large sack (not much) has lost it's appeal. Thanks folks. Neil