Table S4.

Summary of the linear models for the effects of stress treatment and covariates on feather quality in wing and body feathers of nonimplanted yellow-legged gull chicks at 30 d of age

Variable	Primary covers (wing feathers)								Scapulars (body feathers)
	Barb density (TAC)				Barbule density				Barb density				Barbule density
	Estimate	dfn,d	F	P	Estimate	dfn,d	F	P	Estimate	dfn,d	F	P	Estimate	dfn,d	F	P
Intercept	0.369				1.567				0.336				1.522
Brood treatment, control	0.055	1,19	6.307	0.021	0.063	1,19	4.708	0.043	0.031	1,19	3.888	0.063	−0.025	1,19	2.204	0.154
Sex, female	0.004	1,19	0.042	0.841	0.036	1,19	1.689	0.209	0.002	1,19	0.019	0.998	0.002	1,19	0.010	0.923
Chick order, first	−0.021	1,19	0.952	0.342	−0.019	1,19	0.442	0.514	−4.849e5	1,19	0.000	0.892	−0.009	1,19	0.323	0.577

Nonsignificant interactions were removed from full models, and significant terms are highlighted in bold.