From the age of twelve, Ussher attended Portarlington school in County Laois and then Chester.

Following the death of his father and owing to his own delicate health, Ussher returned home to be tutored.

An account of the distribution, migrations and habits of birds as observed in Ireland, with all additions to the Irish list.

He was one of the first authors to contribute to the Irish Naturalist (1892 The crossbill (Loxia curvirostra L.) in Ireland.

Ussher studied the fossil remains of extinct avians and mammals at cave sites in Counties Cork, Waterford, Clare and Sligo in company with English (Henry Seebohm, Howard Saunders, Andrew Leith Adams), French and German ornithologists and vertebrate palaeontologists.