Blake, J. G., J. M. Hanowski, G. J. Niemi, and P. T. Collins. “Hourly Variation in Transect Counts of Birds”. Ornis Fennica 68, no. 4 (December 31, 1991): 139–147. Accessed September 19, 2024. https://ornisfennica.journal.fi/article/view/133327.