I refilled the bird sock with grass seed, which attracted some goldfinches once they realized it had food in it again. However, the local rodents have evidently been able to circumvent the plastic lid baffle I put on the string at the top: it rapidly emptied, with considerable spillage on the ground, which the dog is now pooping out. Sigh. I'd use a real bird feeder if I could figure out what to hang it from.
.