Parasite and brood manipulation effects on nestling growth
For the mass model, we expanded the dataset to include N = 506 nestlings without telomere length information but born in the same period (2012-2017) as the N = 322 nestlings included in the telomere model. In this expanded data set, carnid flies were present in 247 out of the 317 nests and in 708 out of the 828 nestlings. Nestlings gained on average 135.9±1.3g over the 25-day measurement period (Table 1, mass model). Body mass gain was not affected by Carnus presence, and neither was there a significant interaction between brood size manipulation andCarnus presence (Table 1). However, nestlings reared in enlarged broods gained on average 8.9±1.4g less mass than nestlings reared in reduced broods (Table 1, Fig. 4). Mass gain was also significantly different between sexes, with males gaining on average 19.4±1.4g more mass than females (Table 1, Fig. S2).