Table 1. List of species used in the this study indicating sample size, measured colour patches and their human-perceived colours, probable colour production mechanism, probable signaling function as described in the literature and level of chromatic (ΔS_sex) and achromatic (ΔL_sex) sexual dimorphism.

Species	Sample Size		Patch	Human perceived colour	Colour prod. mechanism	Probable signaling function	Sex. dimorph. (jnd)
	males	females					ΔSsex	ΔLsex
Robin	16	15	Back	Brown-grey	Melan.	?	0.52	0.68
Erithacus rubecula			Breast	Rusty-red	Melan.	Ag.-inter.(?)	1.67	0.17
Blackbird	30	10	Head	Black (males), brown (females)	Melan.	?	9.21	13.57
Turdus merula			Back	Black (males), brown (females)	Melan.	?	5.56	8.99
			Breast	Black (males), brown (females)	Melan.	?	8.71	17.4
			Bill	Yellow-orange	Carot.	Q-indic., Ag.-inter., M-choice(?)	9.44	6.8
Blackcap	44	22	Head	Black (males), rusty-red (females)	Melan.	?	16.9	22.08
Sylvia atricapilla			Back	Brown-grey	Melan.	?	1.48	0.59
			Breast	Grey	Melan	?	2.74	0.88
Great tit	27	23	Head	Black	Struct.+Melan.	Q-indic., M-choice	5.81	3.37
Parus major			Back	Green	Carot.+Melan.	?	1.59	1.39
			Breast	Yellow	Carot.	Q-indic.	0.72	3.47
			Cheek	White	Struct	?	0.91	1.08
Blue tit	20	17	Head	Blue	Struct.	Q-indic., Ag.-inter., M-choice	5.25	2.0
Cyanistes caeruleus			Back	Grey-green	Carot.+Melan.	?	2.68	1.53
			Breast	Yellow	Carot.	Q-indic.	1.72	1.53
			Cheek	White	Struct.	?	1.71	1.08
Greenfinch	41	20	Head	Grey-green	Carot.+Melan.	?	4.49	2.68
Carduelis chloris			Back	Grey-green	Carot.+Melan.	?	3.47	2.43
			Rump	Green-yellow (males), green (females)	Carot.+Melan.	?	2.26	1.54
			Tail	Yellow	Carot.	Q-indic.	5.27	3.46
			Breast	Green-yellow (males), brown-green (females)	Carot.+Melan	Q-indic.	8.10	1.87

Colour production mechanisms (melanin-, carotenoid-based, structural colours and combinations thereof) were collated from the literature when known (see Text S1) or determined based on the shape of reflectance spectra following Doucet et al. [61]. Probable signaling function was categorized as: Q-indic. ( = quality indicator, the expression of colour correlates with aspects of individual quality such as condition, health, parental abilities, etc), Ag.-inter ( = agonistic interaction, expression of the colour determines or influences the outcome of aggressive interactions), and M-choice ( = mate choice, male colour expression determines female preferences, measured by traits such as date of egg-laying, paternity, brood sex ratios, differential allocation patterns, etc.). Bibliographic references in support of the probable signaling function of each coloured patch are given in Text S1.