Sample collection in the field
From 2015 to 2022, we captured both fledgling and adult Jackdaws as part of a long-term study of a population breeding in nest-boxes in the Lleida plain, northeastern Iberian Peninsula (Unzeta 2020). We banded each individual with a metallic ring, measured the weight and the length of the tarsus and third primary wing, and took a sample of feathers from the abdomen for genetic analyses. To help developing the library of SNPs, we also used adults found dead during the visits to the nest-boxes. From each individual, we sampled a piece of tissue from the wing shoulder and placed it in Eppendorf tubes. All tissue samples were stored at -20ºC to prevent DNA degradation. Feathers were first stored in glassine bags at room temperature, and selected samples were later transferred to -20ºC freezers to be preserved until DNA extraction. Permits for animal manipulation and sample collections were provided for the Servei de Fauna i Flora from the Generalitat de Catalunya (SF/430-439/2016, SF/0473-0476/2018, SF/0039/2019, 4/2020/MP, SF/0093/21, SF/0018_2/22).