Boyd Alexander was born at Swifts Place, Cranbrook, Kent on 16th January 1873. He was a twin son with Robert Alexander of Lieut-Colonel Boyd Francis Alexander and his wife Mary Wilson and descended from the Alexanders of Ballochmyle in Ayrshire. Colonel Alexander and his wife had had two daughters born in Canada before giving bith to the twin sons. Three more sons followed, the youngest being Claud born in 1878.

Boyd Alexander was educated from 1888 at St Peters College, Radley, and it was during his school holidays that Boyd developed his enthusiasm for ornithology - making a study of the birds of Kent and Sussex. He enlisted in the army, joining the Rifle Brigade in 1893 and in 1896, Boyd and his friend John Springett, a skilled taxidermist, made a comprehensive study of nesting habits and migrations at Rye, which became the basis of probably the finest and most complex collection of Kent and Sussex birds in existence. In 1897 he led a scientific expedition to the Cape Verde Islands where he made an extensive collection of native bird species and, in 1898, went on his first African journey to the Zambezi and Kafuk rivers. He was appointed to the Gold Coast constabulary in 1900, and took part in the relief of Kumasi. In 1904 he led a scientific expedition to Fernando Po where he discovered various new species of birds. The same year saw the commencement of his most important work - an expedition across Africa from the Niger to the Nile accompanied by his younger brother Captain Claud Alexander, the zoologist Captain G.B. Gosling, P. Amaury Talbot and José Lopes. Later that year on 13th November 1904 Claud died of fever after six weeks of illness and was buried at Maifoni in Northern Nigeria. The expedition continued for three years and during this period Boyd surveyed the shores of Lake Chad and explored a considerable part of eastern Nigeria, returning to England by way of the rivers Ubangi, Shari and Nile. For his various discoveries he received gold medals from the Royal Geographical Societies of London and Antwerp, besides honours from other learned societies. In 1908 he returned to Africa for the last time and, during a local disturbance was killed by natives at Nyeri, in Wadai, on 2nd April 2 1910. His body was later recovered by French soldiers and Boyd was buried next to his brother at Maifoni in Northern Nigeria. A memorial to Claud and Boyd Alexander was placed in St Dunstans Church in Cranbrook.

Boyd Alexander published From the Niger to the Nile (1907), besides many articles and papers in scientific and geographical periodicals. His oustanding collection of Kent and Sussex birds was offered by his brother Herbert Alexander to Cranbrook and resides today at the Cranbrook Museum and his collection of 5,500 African birds resides at the Natural History Museum at Tring, Hertfordshire, as well as five manuscript volumes relating to his travel and bird collecting in Africa between 1898 and 1909.