Information on variables: BirdId: ID variable, unique per bird FT: Foraging treatment (either easy or hard) DT: Developmental treatment (either easy or hard) Season: Season of the year (1 = March, 2 = September) Sex: biological sex of the animal (1 = Female, 2 = Male) TimeInTreatment: Time since entering the foraging treatment (in years) StartAge: Age when entering the foraging treatment (in years) Hp: Haptoglobin as measured by colourimetric assay (mg/mL) NOx: Nitric Oxide as measured by colourimetric assay (mmol) Agglutination: Agglutination titre based on serial dilution (scored on a 1-12 scale, average of 2 scores) Ovotransferrin: Ovotransferrin as measured by colourimetric assay (ug/mL) BKA_C: Candida albikans killing assay, expressed as 1- # colonies grown in sample / # colonies grown in control BKA_E: Escherichia coli killing assay, expressed as 1- # colonies grown in sample / # colonies grown in control Redness: Redness of blood, measured at 405 nm AvgStressTime_Pre: Average time between entering the aviaty and puncture of vein (minutes) AvgStressTime_Post: Average time from puncture of vein to last blood collected (minutes) Round: Round of blood sampling, from the 1st early 2018 to the 5th early 2020. Hp_Plate: Plate during Haptoglobin colourimetric assay NOx_Plate: Plate during Nitric Oxide colourimetric assay Ovo_Plate: Plate during Ovotransferrin colourimetric assay BKA_C_Date: Date of C. albicans measure BKA_E_Plate: Plate during E. coli killing assay PreTreatment: Bloodsample taken before entering foraging treatment