“Hormones and behaviour: a comparison of studies on seasonal changes in song production and testosterone plasma levels in the Willow Tit Parus montanus”, Ornis Fenn, vol. 69, no. 1, pp. 1–6, Mar. 1992, Accessed: Nov. 08, 2025. [Online]. Available: https://ornisfennica.journal.fi/article/view/133333