title: RRBS pool of Parus major
design: DNA isolation and purification was done as mentioned in Verhulst et al. (2016). After DNA extraction, the samples were pooled per treatment. Within one pool, none of the samples were, to our knowledge, related to each other. The enlarged and reduced samples were isolated and pooled in 2016 and the control samples were isolated and pooled in 2018. DNA isolation was finalized within one day to prevent batch effects between pools. RRBS was done as mentioned in Derks et al. (2016).