In fall 2023 I measured 56 nest tunnels of European Bee-eater / Bienenfresser (Merops apiaster). 10 in Frauenkirchen, Austria and 46 on the Adriatic island of Susak, Croatia. All nests were found in loess cliffs (artificially erected at St. Martins Lodge, Frauenkirchen, natural on Susak). Measurements were taken with a straight bamboo cane with 1,5 cm diameter on the thicker end).
update 2024: added 26 additional measurements from the 2024 season in Frauenkirchen below. The nest holes in Austria are on average 12 cm longer, probably because of denser material of the nesting cliff? Taking out the three shortest tunnels of each site, to avoid including unfinished tunnels, the Austrian tunnels are even 15 cm longer on average.
