######The data file contains the following sheets: -buckthorn_berry_bush_age_effect: used for the analysis of association between berry production and bush age with year_ID and bush_ID as random effects. -number_of_breeding_pairs: used for the analysis of the association between the number of breeding pairs and buckthorn berry abundance for both great and blue tits. -sleepers_midwinter: used for the analysis of the association between: 1) the number of sleepers and the berry abundance in the same winter 2) the breeding densities and the berry abundance in the winter to come 3) the fraction of roosting females and the berry abundance in the same winter 4) the fraction of young birds roosting and the berry abundance in the same winter 5) berry abundance and winter severity. -recapture_probability: data used to analyze the probability to capture a bird when alive in relation to sex, berry abundance and season. -return_rate: data used to analyze the return rate of three categories of birds: fledglings, females and males in relation to berry abundance. For all categories over the first half of the winter (breeding season to December) and the combined period (breeding season to breeding season) and for females and males (including the first year birds) over the second part of the winter (December to breeding season). -immigrants: data to analyze the immigration rate of first year birds as estimated from the breeding population in relation to berry abundance. -diet: data to analyze the annual variation in diet on the basis of the faeces colour scores in the roosting box in relation to berry abundance. -individual_return_rate: data to calculate return rate on both the individual level (within years) and the annual level in relation to faeces colour scores and berry abundance. -reproductive_rate: data to analyze the association between the reproductive rate in the year before and the year after the berry abundance was measured. ####### Meaning of the data in each sheet ## sheet: buckthorn_berry_bush_age_effect # columns ID: a unique id for the data record bush_ID: a unique id for the bush year: year of measurement berries_per_bush: mean number of berries per bush in December relative_age: age in years relative to 2010 ## sheet: number_of_breeding_pairs #columns Berries_per_bush: mean number of berries per bush in December, the winter before breeding year: year of breeding breeding_pairs: the number of breeding pairs that completed a clutch species: 0 = great tit, 1 = blue tit BCI: beech crop index measured in the preceding winter in Drenthe feeders: 1= feeders available in winter, 0= no feeders available in winter known_breeding_pairs: pairs of which the female was identified hellman: index for winter strength ##sheet: sleepers_midwinter #columns year_dec: year of roost check (December) sleeping_great_tits: number of sleeping great tits in the nest boxes in December berries_per_bush: mean number of berries per bush in December breeding_densities_preceding: the breeding densities in the summer before (in year_dec) in the study area (125 ha) fraction_females: the fraction of the sleeping great tits (column 2) that were female fraction_young: the fraction of the sleeping great tits (column 2) that were first year birds hellman: index for winter strength berryloss: the number of berries that disappeared between the December and the January count. BCI: beech crop index measured in the preceding winter in Drenthe failed: the number of clutches that failed before day 6 divided by the total number of clutches, Z-score ##sheet: recapture_probability #columns year: year of recapture sex: sex, female=1, male =2 season, 0=winter, 1=summer berriec: mean number of berries per bush in December (Z-score) catch: number of birds caught alive: number of birds known to be alive ##sheet: return_rate #columns year_marking: the year that the breeding population and the fledglings were marked/identified during the first brood and that the berries were measured in December year_recapture_and_breeding_count: the year of the recaptures and the estimate of berry related number of breeding pairs berries_per_bush: mean number of berries per bush in December of the year_marking. BCI: beech crop index in Drenthe (60 km distance of the study population) in the same winter as the berries were measured. bird_category: 0=fledgling, 1=female, 2=male number: the number of individually known birds involved in first broods of each category in the year_marking returned: the number of individuals known from the breeding season recaptured in or around nest box in the next breeding season dec: the number of individuals known from the breeding season recaptured as sleepers in December. decbreed: the number of individuals known as sleeper in December recaptured as breeder in the next breeding season density: breeding population size in the year_marking (study plot= 125 ha) hellman: hellman number in the winter of the BCI measurements rprobwi: recapture probability in the winter as calculated from model mrp3 (Supplementary material S3) rprobsu: recapture probability summer as calculated from model mrp3 (Supplementary material S3) ##sheet: immigrants #columns year: year breeding season sex: female=1, male=2 young: 1=first year bird, 0= older bird imm: first year birds not born locally local: locally born first year birds plus older birds that bred in the study area before sum: imm+local fraction: imm/sum berriec: mean number of berries per bush in December (Z-score) ##sheet: diet #column year: year sleeping check (December) sex: female=1, male=2 score 3: number of birds with faeces score 3 n: number of birds scored (score 1,2,3) Fraction: The number of birds with score 3 divided by n berriec: mean number of berries per bush in December (Z-score) ## sheet: individual_return_rate indnr: individual ID plot: plot ID year: year captured sex: female=1, male=2 return_breeding: return next breeding season=1, no return next breeding season=0 berries_per_bush: mean number of berries per bush in December score_DDI: individual faeces score at recapture yearscore_DDY: average year faeces score of all birds recaptured in December ##sheet: reproductive rate year_berry_production: the year that the berries were measured in December berriec: mean number of berries per bush in December (Z-score) mass1: chick mass in the breeding season before the winter the berries were scored (mean per brood, Z-score) number1: chick number in the year before the winter the berries were scored (mean per brood, Z-score) broodmass1: brood mass in the year before the winter the berries were scored (mean per brood, Z-score) mass2: chick mass in the breeding season after the winter the berries were scored (mean per brood, Z-score) number2: chick number in the breeding season after winter the berries were scored (mean per brood, Z-score) broodmass2: brood mass in the breeding season after winter the berries were scored (mean per brood, Z-score)