Nicholson's studies of the Willow Tit, and to a lesser extent the Marsh Tit, resulted in various papers. The following are known to have been published: 'Willow Tit', No.363, 1932; 'On the Distribution and Status of the British Willow Tit', No.12, Vol.30, 1937; and 'Supplementary Notes on the Distribution and Status of the British Willow Tit', No.4, Vol.31, 1937. In addition, he corresponded with others on the distribution of the Willow Tit and its song, especially compared to the Marsh Tit.