[4] Birtwhistle won the Men's PR3 Single Scull at the 2021 Australian Rowing Championships.
[3] He won the PR3 Men's Single Scull event as part of the International Rowing Regatta, which was run alongside the 2021 Final Qualification Regatta in Gavirate, Italy.
[5] At the 2020 Summer Birtwhistle was a member of the PR3 Mix 4+ along with James Talbot, Nikki Ayers, Alexandra Viney.
[6] With Jessica Gallagher, Alexandra Viney, James Talbot and Teesaan Koo under the canvas, Birtwhistle finished fourth in the PR3 Mixed Coxed Four at the 2022 World Rowing Championships.
[7] At the 2023 World Rowing Championships, Birtwhistle, alongside his crew of, Harrison Nichols, Jessica Gallagher, Susannah Lutze, and cox Teesan Koo finished fourth in the PR3 Mixed Coxed Four.