On grassy shingle banks at this time of year there are frequent piles of small stones mounded outside of small holes. The photo shows a new one in my garden with a pile, about 40cm across, of small stones (there is a 50p coin in the photo and the entrance is top centre). I have often wondered what made these and a Trail Camera has provided the answer. It is a pair of Long-tailed Field Mice but I find it hard to imagine them moving these 1,000+ stones one by one from under the ground to outside their front door. The video shows them in front of the entrance and one is taking in nest material, so it looks like the main construction phase is over and they are now fitting it out with nest material.
This cosy nest has a good chance of being taken over by a Bumblebee queen, but then it will be vulnerable to Badgers – as was the nest about a metre from this location during the summer – below.