Davidson Black kept a diary throughout much of his adult life. There are 28 volumes in this series. The earliest is for 1902, the year he entered medicine at the University of Toronto; it includes a tally of monthly expenses. The last diary is for 1934, the final entry being for 9 March, six days before his death. For each of the years 1922 and 1925, there are two volumes of diaries. There are no diaries present for the years 1907, 1908, 1909, 1911, and 1912. The diary Davidson kept while on active service during World War I is filed with his service records in Series 4. Most of the entries are brief as the diaries, except for 1902, are small. Some of the loose entries with the diaries are longer.
A number of items document his personal activities. The earliest is a small well-thumbed copy of 'The Book of Common Prayer', presented to him by his mother on his 9th birthday in 1893. A notebook, a journal, and permits document his early interest in ornithology. Finally, there are files of memorabilia, poems and sketches, and on honours bestowed on him later in life, along with twelve diplomas and certificates.