[1] Cassels lived in Red Deer, Alberta and became a recognised authority across Canada on migratory birds who exchanged information (from detailed observations from 1920 to 1935), with the leading (male) ornithologists of her day,[2] 'her keen enthusiasm stimulated a wide interest in ornithology'.
[7] Cassels life was based in a log cabin and she developed local nature trails,[2] she identified birdsongs and was a self-taught violinist,[7] called 'a woman of charm and culture' in her obituary.
Cassels was among the volunteer ornithologists whose field research[8] made them among the 'outstanding individuals..who spent entire lifetimes learning about [Alberta] province's flora and fauna and sharing that knowledge with others.
[11] Cassels was self-educated from her own observations[12] and over a period of fifty years keeping diaries on migratory birds[2][3] enjoyed correspondence with national institutes[13] and engagement with key Canadian ornithological contacts such as Percy A. Taverner of the Victoria National Museum, Ottawa and William Rowan of University of Alberta, Edmonton,[14] who was a lifelong friend, and whom Cassels helped establish the Gaetz Lakes Sanctuary.
Her spotting the gyrfalcon, the first record of this species in Alberta, killed in a homestead for attacking turkeys in a domestic setting in 1920, was referred to her own 1922 work and even remarked upon in 1961.
Cassels helped practical developments like purple martin colonies at Sylvan Lake,[2] although attempts were made to have the Red Deer River Canyon designated as a provincial park in 1906, this was not supported.
[6] Cassels' work is still cited in modern publications such as Bibliography of Alberta Naturalists, from her notes in The Canadian Field-Naturalist, which in her obituary, said that by ' her keen enthusiasm, she stimulated a wide interest in the study of ornithology.