Reuter, T., Nedstam, B. and Ruotanen, T.-O. (1980) “Observations of interlocked Swifts Apus apus and A. affinis”, Ornis Fennica, 57(3), pp. 132–133. Available at: https://ornisfennica.journal.fi/article/view/133045 (Accessed: 23November2024).