ID = Individual identity (ring number) Season = Breeding season year and the preceding winter Arrival_date = Date and time of first detection in a particular season (central European Standard time) first_capture = Date and time of first ever capture in the study site (central European Standard time) second_detection = Date and time of second detection in a particular season (central European Standard time) sex = Sex of individual (male/female) brStatus = Breeding status of individual in a particular season (breeder/non-breeder) recruit = Binary variable. 1 = yes (born in the study site in a previous season), 0 = no (not born in the study site) date_fledged = Date an individual recruit fledged from their natal nestbox in a previous season tarsus = Tarsus length (mm) bred_prev_yr = Binary variable. 1 = yes (bred in the study site in the previous season), 0 = no (did not breed in the study site in the previous season) laying_date = Date of first egg of a female breeder in a particular season clutch = Number of eggs laid in the clutch of a female breeder in a particular season chicks_fledged = Number of chicks fledged from the clutch of a female breeder in a particular season EPP_gain = Number of extra-pair offspring gained by a male in a particular season EPP_loss = Number of offspring in a male breeder's social nestbox sired by an extra-pair male in a particular season ID_mate = Individual identity (ring number) of a female breeder's social mate in a particular season