I suspect that we have an infestation of some sort of grub, but surely it can't be birds causing this level of damage?
It happens during the night. The damage that can be seen in the photo (and more) happened over the last two nights. At this rate, the entire lawn will be gone in a week.
Should I just resign myself to having to let the lawn get completely destroyed, looking at a muddy mess all winter, and reseeding in the spring? It's only a lawn, and grass will grow again, but it's still surprisingly upsetting.