NOTE: In each file, NA in a cell refers to a missing data point. An empty cell refers to cases where no data collection was attempted in a given year (e.g., CORThatch was only collected in 2016). FILE NAME: female_measurements COLUMN HEADINGS Band#: Last 5 numbers of a female's metal leg band nest: nest box number. site: Nature Area, or Sewage Lagoon, SL. implant: treatment group (CORT: CORT-filled implant; control: empty implant; none: no implant). Note, in the associated manuscript, "Control" refers to individual birds that did not have an implant; while "Sham" refers to individual birds that had an empty implant. implant_status: females who retained implants into first week of incubation, in, or females who lost implant, out. Note that birds that did not receive an implant (i.e., implant "none") were also listed as "in" to allow for inclusion in analyses with birds that had received an implant. age: maternal age (second-year, SY, or after-second-year, ASY). return_rate: females who returned to the breeding site the following year, 1, and females who did not return, 0. visits_f_clutchsize: female nest box visits per chick per hour on day 8 or 9 post-hatch. visits_m_clutchsize: male nest box visits per chick per hour on day 8 or 9 post-hatch. clutch_size: Number of eggs in clutch. egg_mass: combined mass (in grams) of all eggs in clutch; each egg was measured on the day it was laid. implant_to_bloodsample: Number of days between female receiving implant and blood sample being taken during incubation. weight1: female mass (in grams) at the time an implant was inserted during nest building. wing: female flattened wing length (in mm). CORTinc: female blood plasma corticosterone level during the first week of incubation (ng/ml). time1: time (in seconds) for CORTinc blood sample to be collected (from when the female entered the nest box). time2: time (in seconds) for CORThatch blood sample (from when the female entered the nest box). CORThatch: female blood plasma corticosterone level collected during the first week post-hatch (ng/ml). date_firstegg: lay date of first egg in the clutch in Julian days (Jan 1st = Day 1). year: year of study (2015 or 2016). number_fledged: number of chicks that survived to fledging. Notes:additional comments on an individual FILE NAME: nestling_measurements COLUMN HEADINGS Band#: Last 5 numbers of a female's metal leg band nest: nest box number. site: NatureArea, or Sewage Lagoon, SL. treatment: treatment group of mother (CORT: CORT-filled implant; control: empty implant; none: no implant). Note, in the associated manuscript, "Control" refers to individual birds that did not have an implant; while "Sham" refers to individual birds that had an empty implant. hatch_suc: egg that hatched, 1; or did not hatch, 0. fledge_surv: chick that survived to fledging, 1; or not, 0. clutch_size: Number of eggs in clutch. m_age: motherŐs age in year of study (second-year, SY; after-second-year, ASY). CORTin: motherŐs blood plasma corticosterone level collected during the first week of incubation (ng/ml). CORThatch: motherŐs blood plasma corticosterone level during the first week post-hatch (ng/ml). H14: individual nestling mass (in grams) 14 days post-hatch (Hatch day = Day 0). implant_status: whether implant remained in the mother until her recapture at incubation, in; or fell out prior to her recapture at incubation, out. Note that birds that did not receive an implant (i.e., implant "none") were also listed as "in" to allow for inclusion in analyses with birds that had received an implant. day3mass: mass of chick on day 3 post-hatch. day7mass: mass of chick on day 7 post-hatch. growth_3_to_7: nestling mass gain (g/day) between day 3 and 7 post-hatch. sex: nestling sex (m/f). year: year of study (2015 or 2016). Notes:additional comments on an individual FILE NAME: females recaught vs non-recaught COLUMN HEADINGS Band#: Last 5 numbers of a female's metal leg band Age: female's age (second-year, SY, or after-second-year, ASY). nest captured: nest box in which female was initially captured nest laid: nest box in which female laid eggs (if left blank, we found no evidence the female laid eggs) recaught: females that received an implant during nest building and were recaptured during incubation, yes; or were not recaptured, no. recaught (1/0): females that received an implant during nest building and were recaptured during incubation, 1; or were not recaptured, 0. treatment: treatment group of mother (CORT: CORT-filled implant; control: empty implant; none: no implant. For details on the single female categorized as "none" see Notes column). Note, in the associated manuscript, "Control" refers to individual birds that did not have an implant; while "Sham" refers to individual birds that had an empty implant. year: year of study (2015 or 2016). implant in/out: whether implant remained in the mother until her recapture at incubation, in; or fell out prior to her recapture at incubation, out. eggs laid: Whether the female laid eggs (yes) or did not lay eggs (no) eggs hatch: Whether at least one of a female's eggs hatched (yes) or none of her eggs hatched (no) Notes:additional comments on an individual