Table 2. Analysis of the effect of ectoparasite load manipulation (parasites), methionine supplementation (methionine) and interaction between these treatments on growth of blue tit nestlings during the period of methionine supplementation (days 3–6) and immediately after termination of supplementation (days 6–9, day 9).

factor	body mass gain, days 3–6 N = 409			body mass gain, days 6–9 N = 383			body mass on day 9 N = 383
	df	F	p	df	F	p	df	F	p
parasites	1, 40	0.85	0.36	1, 40	5.21	0.03	1, 40	5.30	0.02
methionine	1, 365	8.24	0.004	1, 339	4.51	0.03	1, 339	0.10	0.73
interaction	1, 365	0.83	0.36	1,339	5.12	0.02	1, 339	0.46	0.46

Statistics of a linear mixed model with brood nested in parasite treatment fitted as a random effect; variance component, its standard error and percentage of variance explained by brood effect nested in the parasite treatment is shown. N equals the number of nestlings measured.