Halupka, L. “Nest Defence in an Altricial Bird With Uniparental Care: The Influence of Offspring Age, Brood Size, Stage of the Breeding Season and Predator Type”. Ornis Fennica, vol. 76, no. 3, Sept. 1999, pp. 97–105, https://ornisfennica.journal.fi/article/view/133504.