Alexander spent most of his time in India and became interested in its birds in 1927. Ornithology at that time was not popular among Indians in India, and when Horace informed Gandhi of an expedition, Gandhi commented, That is a good hobby, provided you don't shoot them. Horace demonstrated the use of binoculars as an acceptable alternative to the gun and carried them at most times. Horace Alexander joined Sidney Dillon Ripley on an expedition to the Naga Hills in 1950. Ripley named a subspecies of the aberrant bush warbler after Alexander, although this is no longer recognised. In the same year he founded the Delhi Birdwatching Society, along with Lt. Gen. Harold Williams. One of the early members of the organisation was the young Indira Gandhi, and the group encouraged Indian ornithologists such as Usha Ganguli. Many of his notes were mislaid when one of his suitcases was lost in India in 1946. Through his influence on Jawaharlal Nehru, he was instrumental in the designation of the Sultanpur Bird Sanctuary near Delhi.