Large hardback diary chiefly containing records of bird sightings with notes on eggs found. Other natural history observations and details, such as locations visited on walks and bicycles rides, descriptions of the weather etc are also included.

The volume appears to be an amalgation of more than one diary: entries for 1918 start at the front of the volume and appear to be in chronological sequence, while those for other years are dispersed among the remaining pages. The bulk of the entries are for 1917 and 1918.

In a few places there are brief notes which Nicholson has added at a much later date, often giving the town where his family were living at the time.