He was born the elder son of Charles Bell Horsbrugh, a captain and Adjutant of the 2nd Central India Horse.

While stationed in Sierra Leone he became a lifelong member of the Avicultural Society of Great Britain, occasionally contributing articles to their journal.

He also raised two grey parrots that became his constant companions and learnt to talk, as well as a turaco that regularly shared an early morning bath with him.

In June 1905 his younger brother, C. B. Horsbrugh (1874–1952), joined them on Naval Hill, but soon took up employment with the Transvaal Museum in Pretoria under Dr. J. W. B. Gunning.

On the train trip from Bloemfontein to Cape Town, Boyd Horsbrugh travelled in the guard's van to ensure the proper feeding and care of his charges.

When C. B. Horsbrugh returned to England in 1907, he also took along a considerable collection of live South African birds, causing great excitement in the avicultural world.