Table 1.

Population level differences in immune indices between annual cycle stages (ACS) between the wet and dry season in female and male Common Bulbuls Pycnonotus barbatus. Birds were sampled over two annual cycles in Nigeria. Sexes were analysed separately. Annual cycle stages were determined based on occurrence of brood patch and feather quality: breeding, moulting and non‐breeding and non‐moulting birds. Individuals sampled in both breeding and moult conditions were excluded from analyses. All individuals that were repeat sampled were also excluded

	Factor	df	HP		NOx		OVO		AGG		Lysis
			F	p	F	p	F	p	F	p	LRT	p
Females	Batch	1	7.46	0.01	0.79	0.38	145.37	<0.01	4.59	0.03	1.15	0.28
	Body mass	1	3.06	0.08	0.02	0.89	0.55	0.46	0.43	0.51	1.02	0.31
	Date	1					1.24	0.27	2.68	0.10	2.33	0.13
	ACS	2	0.70	0.50		a	1.97	0.14	0.53	0.59	0.62	0.73
	Season	1		a		a	6.78	0.01**	1.77	0.18	11.55	<0.01***
	Season:ACS	2	0.47	0.62	3.05	0.04*	0.70	0.50	1.74	0.18	0.51	0.77
	Season:Date	1	15.96	<0.01***	8.20	<0.01*	0.15	0.70	0.00	0.97	0.21	0.64
Males	Batch	1	38.47	<0.01	0.03	0.86	82.80	<0.01	0.77	0.38	1.07	0.30
	Body mass	1	2.42	0.12	0.04	0.85	0.01	0.91	2.64	0.11	0.01	0.94
	Date	1					0.80	0.37	16.92	<0.01***	0.67	0.41
	Moult (M)	1	0.33	0.56	4.41	0.04*	0.02	0.89	0.26	0.61	1.10	0.29
	Season	1		a		a	0.13	0.71	13.78	<0.01***	6.81	0.01**
	M:Season	1	0.25	0.62	0.04	0.84	0.25	0.62	2.06	0.15	1.55	0.21
	Season:Date	1	15.69	<0.01***	7.19	0.01**	2.25	0.14	0.04	0.85	0.03	0.86

AGG: haemagglutination and lysis—haemolysis; HP: haptoglobin concentration; NO_x: nitric oxide concentration; OVO: ovotransferrin concentration.

Summary statistics with significant p‐values are highlighted bold. * indicates level of significance: *p < 0.05; **p < 0.01; ***p < 0.001.

^aDifferences determined by post hoc tests due significant interaction between variables.