There are now four eggs in the nest. The pattern seems to be that the bluetit arrives for the night soon after 7.00pm and spends about ¾ of an hour turning the eggs and generally preparing for the night. The eggs must be more robust than I thought because they get some pretty rough treatment. We watched the whole performance last night and were surprised by the energy it took. First there were some normal nesting wriggles. Whether she trod on the eggs or splayed her legs to avoid them we could not see, but it looked normal enough. Then she would stick her head between her legs to do something to the eggs beneath her. We presume that she must be turning them to equalise their temperature. This process is done so enthusiastically that she often flips over on to her back! It looks exhausting as well as undignified so presumably has a significant value - the reasonably simultaneous hatching of her eggs. After a bit of egg turning, she lies on top of them, resting, for a minute or so. Then the whole process starts again.