Sample population and colour scoring of tawny owls
Our sample size consisted of 371 individuals from a population in Uusimaa, southern Finland. The pool of samples included 69 breeding pairs and their respective offspring, sampled from 2009 until 2021 during the annual monitoring of nesting boxes in the area during breeding season. Blood was collected from each individual during the ringing activity, with a sterilized needle and immediately submerged in SET buffer. Colour phenotyping according to (Karell et al., 2011). Geographic location and composition of each family (breeding pair and offspring) is available as supplementary material (Table S1).