This series covers the period 1927-2000, and reflects the range of speaking engagements that Nicholson undertook.

The sequence of material begins with a draft of Nicholson's first public talk in 1927 on the Oxford Bird Census. Many lectures to ornithological organisations, national and regional, are documented; some significant ones include the Bernard Tucker Memorial Lectures, 1961 and 1976, the Witherby Memorial Lecture (British Trust for Ornithology), 1971, and a lecture given to the American Ornithologists' Union, 1980.

There are lectures on ecology and environmental issues given to a wide variety of organisations and audiences, such as the Horace M. Albright Lecture at the University of California, 1964, a series of three Esmee Fairbairn Lectures at King's College, London, 1980, and the 'First World Conservation Lecture' at the Royal Institution, 1981. After-dinner speeches and speeches given opening ceremonies are included.