Of course I cannot be certain about my observations as I have only been observing successfully since March 2nd, i.e. just under a week. Some patterns have however come to my attention.
The most traffic has so far taken place in the morning. The Eurasian Tree Sparrow seems to have a liking for the 8-9 o'clock slot and multiple visits are made within the hour. Frequently two visits are in rapid succession during which the bird examines the nest, makes room, flattens the content, moves twigs and feathers, flies out of the hole only to perch again at the entrance, re-enter and repeat the above.
The Great Tit and Blue Tit come at more random hours, which might mean that multiple birds of these two species have visited the nest.
No visits have so far taken place during 12-14 o'clock. No visits have so far taken place after ca. 16 o'clock. Of course the days are still quite short (sunrise 06:53; sunset 18:14) and considering the bitter-cold weather, the birds will wait some more before they start laying eggs. After a week of temperatures above 0°C, they dropped again to below zero and a snow storm paid visit on Friday night and Saturday bringing 5-10 cm of fresh snow. According to the weather forecast the temperatures will remain below zero with only slight increases towards the end of this coming week but with more snow again next Saturday.
In the meantime I observe and wonder what they do, where they go, how they plan their rounds.