Sweetcorn at risk from a plague of rodents?

Every year I give you a photo of a huge combine harvester looming out of the dust and rumbling past the edge of our garden. Well not this year, for the air was still and the combine was for some reason much quieter.
Before I knew it, the wheat field next to us looked like this.

 The very next day it looked like this.

Nowhere to hide

Last year this spelled curtains for my sweetcorn crop. We quickly harvested what was ripe, but the rest got devoured overnight by field mice and/or rats, which flee the openness of the freshly cut field dodging the watchful eyes of kestrels and buzzards, and head straight onto our farm.

A kestrel and a rook captured in the skies above the
newly harvested field. Rooks are uncommon on the farm.

Last year five traps in the polytunnel caught five field mice the morning after the straw was baled up. It's not nice and they are beautiful creatures, but I have to do something to protect my crops. So two days ago had me rushing about setting mouse traps and laying rat poison (if you hit them hard straight away, it saves much bigger problems later on and minimises the amount of poison getting into the ecosystem).
This is not pretty stuff, but it is part of the reality of rural life.

So this morning I rushed out to check the traps and to check my sweetcorn, for it has been slow this year and none of it is yet ready for harvest. Just one vole in the polytunnel, which may explain the nibbled carrot tops I found yesterday and so far no damage to the sweetcorn. We'll see what happens over the next couple of days. Fingers crossed.