The effect of pre-laying maternal immunization on offspring growth and immunity differs across experimentally altered postnatal rearing conditions in a wild songbird

Table 1 Results of analyses on early and late nestling growth, fledgling body mass and tarsus length

Sources of variation	df	F	P
Early nestling growth (g per day); N = 352
Year	1, 51.28	9.74	0.003
Maternal immunization	1, 21.43	0.09	0.767
Brood size manipulation	1, 46.48	0.93	0.339
Nestling status	2, 83.99	0.12	0.888
Offspring sex	1, 300.93	6.80	0.010
Hatching date	1, 50.68	5.33	0.025
Hatchling body mass	1, 302.87	488.34	< 0.001
Square-transformed late nestling growth (g per day); N = 281
Year	1, 37.99	0.06	0.805
Maternal immunization	1, 22.13	0.80	0.381
Brood size manipulation	1, 34.93	11.96	0.001
Nestling status	2, 73.25	0.75	0.474
Offspring sex	1, 244.12	28.12	< 0.001
Hatchling body mass	1, 247.91	339.78	< 0.001
Maternal immunization × brood size manipulation	1, 230.37	7.47	0.007
Fledgling body mass (g); N = 281
Year	1, 36.13	3.84	0.058
Maternal immunization	1, 20.71	0.55	0.468
Brood size manipulation	1, 39.20	18.96	< 0.001
Nestling status	2, 66.04	0.54	0.586
Offspring sex	1, 233.14	50.85	< 0.001
Hatchling body mass	1, 242.28	26.94	< 0.001
Maternal immunization × brood size manipulation	1, 226.81	7.78	0.006
Maternal immunization × offspring sex	1, 230.44	2.99	0.085
Fledgling tarsus length (mm); N = 281
Year	1, 30.46	0.04	0.842
Maternal immunization	1, 35.73	2.86	0.099
Brood size manipulation	1, 32.31	1.84	0.184
Nestling status	2, 78.58	0.64	0.530
Offspring sex	1, 259.34	33.00	< 0.001
Hatchling body mass	1, 263.82	6.21	0.013
Maternal immunization × brood size manipulation	1, 232.86	5.83	0.017

Table 1 presents the results of linear mixed models that examined the effects of a set of explanatory variables on early nestling growth, square-transformed late nestling growth, fledgling body mass and fledgling tarsus length. Full models included year (to control for inter-season differences), maternal immunization (control vs. immunized females), brood size manipulation (control vs. enlarged broods), nestling status (to control for cross-fostering effects; there were three levels of this factor: nestlings from cross-fostered nests moved to foster broods, nestlings from cross-fostered nests that stayed in their original broods and nestlings from non-cross-fostered nests where all nestlings stayed in their original nests) and offspring sex (to control for differences between male and female nestlings) as fixed factors, and hatching date, clutch size and hatchling body mass (2 days after hatching) as covariates. All two-way interaction terms between maternal immunization, brood size manipulation and offspring sex were tested as well. Nest of origin (female identity) and nest of rearing (foster female identity) were included in all models as random factors (results not shown). Presented are reduced models after sequential backward elimination of non-significant (if P ≥ 0.10) interactions and covariates

ISSN: 1742-9994