README file for individual sparrow data for Pepke et al. (2022) Causes and consequences of variation in early-life telomere length in a bird metapopulation, Ecology and Evolution. Below is a short explanation of variables in each coloumn. For details see the Methods section in the main text. NA indicates missing data. ID : individual identity number year : year of hatching date : date of telomere sampling TL : relative telomere length pop_size_meancentered : spring pre-breeding census population size in the hatch year mean centered within populations island_name : name of natal island island_ID : identity number for natal island brood_ID : brood identity number sampling_age_days : age in days at telomere sampling clutch_size : number of chicks in the nest at telomere sampling sex : male = 1 and female = 2 tarsus : tarsometatarsus (tarsus) length measured in mm mass : body mass measured in grams tarsus_agecorrected : age-standardized tarsus length (i.e. residuals of a tarsus vs. age model, see Methods) condition : body condition (residuals of a linear regression of log10-transformed mass against log10-transformed tarsus length) hatch_date : date of hatching hatchday_meancentered : date of hatching (mean centered ordinal day of the year) firstyear_survival : indicates whether an individual survived first year (0 = no, 1 = yes) min_lifespan_days : minimum observed lifespan measured in days censored : indicates whether an individual is censored (i.e. still alive at the end of the study) in survival analyses (censored = 1, not censored = 2) dispersal : indicates whether an individual dispersed to another island during its first year (= 1, natal dispersal) or not (= 0)