Banbura, J., and P. Zielinski. “Timing of Breeding, Clutch Size and Double-Broodedness in Barn Swallows Hirundo Rustica”. Ornis Fennica 75, no. 4 (December 31, 1998): 177–183. Accessed November 22, 2024. https://ornisfennica.journal.fi/article/view/133490.