Table 1. Numbers of individuals with different classes of iris colour in the studied species; % percentage of birds aged correctly by the iris colour.

Class 1 = grey iris, class 2 = brown iris, class 3 = iris colour intermediate between grey and brown.

Species	Iris colour
	immatures					adults
	class 1	class 2	class 3	total	%		class 1	class 2	class 3	total	%
Great Tit	54	0	4	58	93.1	0	21	3	24	87.5
Parus major
Eurasian Blue Tit	25	0	2	27	92.6	0	10	1	11	90.9
Cyanistes caeruleus
Common Chiffchaff	33	0	0	33	100	0	5	0	5	100
Phylloscopus collybita
Long-tailed Tit	92	0	4	96	95.8	0	0	0	0	–
Aegithalos caudatus
Goldcrest	535	0	12	547	97.8	0	58	18	76	76.3
Regulus regulus
Eurasian Treecreeper	21	0	0	21	100	0	2	0	2	100
Certhia familiaris
Winter Wren	64	0	0	64	100	0	0	2	2	0
Troglodytes troglodytes
European Robin	217	0	1	218	99.5	1	35	20	56	62.5
Erithacus rubecula
Common Blackbird	116	1	3	120	96.7	1	32	6	39	82.1
Turdus merula
Total	1157	1	26	1184	97.7	2	163	50	215	75.8