Claude Henry Baxter Grant, an ornithologist at the British Museum (Natural History) for many years, was called up for service in the Anglo-Boer War of 1899-1902. During his stay in South Africa he made a valuable collection of birds around Deelfontein, a railway station southwest of De Aar, where there was at the time a large surgical and convalescent camp. After the war, in 1903 or 1904, he returned to southern Africa to collect zoological specimens for the British Museum in Little Namaqualand, Zululand, Mozambique and other parts of the sub-continent. His explorations were financed by Charles D. Rudd*, and duplicate specimens were supplied to the South African Museum in Cape Town.
The birds that Grant collected included three new species, which he described in 1908: Heteromirafra ruddi (Rudd's Lark) collected at Wakkerstroom, near the Transvaal-Natal border, and Apalis ruddi (Rudd's Apalis) and Cinnyris meergaardi (Neergaard's sunbird), both collected at Coguno in southern Mozambique. The rest of his collection was described by W.L. Sclater* in The Ibis during 1911-1915. Three lists of the mammals he collected were published by the British expert Oldfield Thomas and collaborators in the Proceedings of the Zoological Society, dealing with specimens from Knysna (1906), the Gorongoza Mountains (now Serra da Gorongosa) in Mozambique (1908), and Tete, Mozambique (1908). In addition Grant also collected freshwater fishes, reptiles and amphibians. His collections of batrachians and reptiles, presented to the British Museum by his sponsor Rudd, were described by G.A. Boulenger* in the Proceedings of the Zoological Society in 1905 and 1907. Grant became a member of the South African Ornithologists' Union in 1905.
In 1915, still in the Bird Department of the British Museum, Grant expressed some criticism of Austin Roberts's* tendency to create new genera and sub-species of southern African birds. These concerns were repeated in his review of Roberts's Birds of South Africa (1940). From 1921 to 1924 he was stationed in the Kasulu sub-district of the Uha region of Tanganyika (now part of Burundi) and in 1925 contributed a description of the Uha region to the Geographical Journal. In his later years, as co-author with C.W. Mackworth-Praed, he participated in the compilation of two major works: Birds of eastern and north eastern Africa (London, 1952-1955) and Birds of the southern third of Africa (2 vols; New York, 1962-1963).