Thanks. No, most of the seed is visible on the surface. I did sprinkle
some potting soil over it, but this has been watered down below,
leaving the seeds on the surface.

Yes, I probably seeded too early. I put some bird netting over the area
and will wait for it to warm up a bit, at which time I'll water
frequently. I assume that the seed hasn't been damaged so far by
sitting in the cold, right?