We just seeded and fertilized the lawn today - and yeah, I would maybe wet it in, but my chickens went out and picked at a piece or two and spit them right out (we had just the 10-10-10 out there, pelleted).
I was a little worried myself, but they haven't eaten it at all, really.
MY DH and I fertilized a part of the lawn for the birds. After we fertilized, we watered the area well for a few days before we let the birds roam there. They didn't seem interested in the fertilizer and we noticed nothing unusual with the birds. We kept watering the area after we let the birds roam the area. I even had to mow it.