###Readme for the data file "Salmon_et_al_2021_wide_RSPB-2021-1118.csv" family: nest identifier in each breeding batch. mass_"t"d: Individual body mass at age category "t"in g. tarsus_"t"d: Individual tarsus length at age category "t"in mm. age_"t"d: Exact age in days at "t" age category. rank: Hatching rank within the clutch (1:1st or 2:2nd). nr_siblings_5d: number of siblings in the nest at 5 days after the hatching of the first egg. sex: female: F or male: M. first_phase_diet: diet treatment between hatching and 7 days (H: high protein content; L: low protein content). second_phase_diet: diet treatment between 7 and 15 days (H: high protein content; L: low protein content). mass_rate_7d: Body mass gain rate (g/d) between age category "0d" and "7d". mass_rate_15d: Body mass gain rate (g/d) between age category "7d" and "15d", experimental period. mass_rate_30d: Body mass gain rate (g/d) between age category "15d" and "30d". telomere_Kb_7/15d_LabRound1: Red Blood Cell telomere length in Kb at 7/15 age category measured in the first independent laboratory round. telomere_Kb_15/120d_LabRound2: Red Blood Cell telomere length in Kb at 15/120 age category measured in the second independent laboratory round. gel_LabRound1/LabRound2: Gel identity in each correspondent independent laboratory round. telomere_loss_7_15d/telomere_loss_15_120d: Telomere loss rate (bp/d) in the corresponding elapse of time, i.e. 7-15d or 15-120d.