Series of seven hardback ring-binders. Notes chiefly in Nicholson's hand, with some typescript notes.

Each volume contains Nicholson's detailed notes on bird sightings, arranged alphabetically by species. The volumes are labelled on the spine in a continuous alphabetical sequence from 'A' to 'W' (one for 'Y', 'Z' was not found). The entries for each species give dates and locations of sightings (sequence is chronological), usually followed by further notes on a species' distinguishing features; sometimes information on eggs found is included. They cover sightings from trips abroad as well as many parts of the UK. A small number of photographs of birds and nests are found, stuck to pages with adhesive, in a few of the volumes.

The volumes have been used over several decades, additional pages of notes having been added over time. The bulk of the entries are from the 1920s; very few are post 1950s. It appears that Nicholson began writing up these notebooks in c.1918-1920, though there are a few references to earlier bird sightings (c.1916). It seems likely that he copied some of his very early records into these notebooks.