He began his scientific studies under a private tutor when his family moved to Krems an der Donau, and to Schloss Arntsdorf after his father's death when he was 17.

[1] Tschusi collected about 10,000 specimens over his life, which are now in the Imperial Natural History Museum, the Zoologische Staatssammlung München, and the Salzburg Ornithological Institute.

Tschusi specialized in the avifauna of the Palaearctic, becoming a noted expert on the subject, and exerted a great influence on the development of ornithology in Austria-Hungary.

[1] Tschusi's son Rudolf von Thanner was also an ornithologist, and became an expert on the birds of the Canary Islands and the other parts of Macaronesia.

His fortunes changed around his golden wedding anniversary in 1921, when he was granted a pension by the Austrian government and received an honorary doctorate from the University of Innsbruck.