YR = Year 

PID = Individual pull ID

NY = Nest ID on each year

SG = Synchronous group

EG = Experimental group

CR = Rank of the nestling (the nestling that hatched first was assigned the highest rank, i.e., rank 1)

SX = Sex of the individual (0 = females, 1 = males)

BM = Body mass (g)

TL = Tarsus length (mm)

AG = Age of the nestling at the time of measuring 

BS = Brood size

LD = First laying date (date when the first egg of the clutch was laid, date 1 = JAN 1)

PM = Maximum number of ectoparasites detected in the nestling (0: no visible flies, 1: 1–3 flies, 2: 4–6 flies, and 3: >6 flies)