Table 3. F-, p-values and parameter estimates for the analyses of covariance between life-history traits (dependent variables) of breeding female great skuas (Stercorarius skua) and winter feather corticosterone levels (pg/mm) and breeding colony (i.e., Bjørnøya, Iceland and Shetland) used as independent variables (additive model excluding the interaction).

INDEPENDENT VARIABLES	Feather corticosterone		Colony		Parameter estimates
Dependent variables:	F value	p value	F value	p value		Value	s.e.	t value	p value
1/Body mass (g)	1.43	0.24	2.48	0.09	Intercept	1406.76	26.65	52.79	<0.0001
					Feather corticosterone	1.11	0.93	1.20	0.24
					Colony (Iceland)	26.60	20.66	1.29	0.20
					Colony (Shetland)	−22.64	22.28	−1.02	0.31
2/Laying date (julian date)	0.01	0.93	147.57	<0.0001	Intercept	168.55	1.87	90.09	<0.0001
					Feather corticosterone	0.01	0.06	0.09	0.93
					Colony (Iceland)	−24.42	1.49	−16.33	<0.0001
					Colony (Shetland)	−19.78	1.52	−13.05	<0.0001
3/Initial clutch size (eggs)	0.41	0.52	15.17	<0.0001	Intercept	1.63	0.11	15.32	<0.0001
(CSini)					Feather corticosterone	0.00	0.00	−0.64	0.52
					Colony (Iceland)	0.42	0.08	5.10	<0.0001
					Colony (Shetland)	0.37	0.09	4.24	<0.0001
4/A-egg length (mm)	3.68	0.06	9.50	<0.0001	Intercept	70.19	1.03	68.12	<0.0001
					Feather corticosterone	−0.07	0.04	−1.92	0.06
					Colony (Iceland)	3.30	0.80	4.14	<0.0001
					Colony (Shetland)	2.61	0.83	3.14	<0.01
5/B-egg length (mm)	2.66	0.11	12.72	<0.0001	Intercept	68.36	0.99	69.34	<0.0001
					Feather corticosterone	−0.05	0.04	−1.63	0.11
					Colony (Iceland)	4.02	0.81	4.94	<0.0001
					Colony (Shetland)	1.86	0.85	2.18	0.03
6/Chicks fledged	0.10	0.76	11.06	<0.0001	Intercept	0.08	0.15	0.57	0.57
					Feather corticosterone	0.00	0.01	0.31	0.76
					Colony (Iceland)	−0.06	0.11	−0.50	0.62
					Colony (Shetland)	0.46	0.12	3.89	<0.0001

Parameter estimate values are given for the following factor: Colony: Bjørnøya. Numbers in bold indicate significant p-values (p<0.05). s.e., standard error.