Table 7.

Element concentrations (in milligrams per kilogram) in the eggshells of black-headed gulls breeding in five colonies in northern Poland in 2015

	Skoki Duże (15)		Koronowo (18)		Bydgoszcz (18)		Pakość (18)		Kusowo (18)
	Mean	SD	Mean	SD	Mean	SD	Mean	SD	Mean	SD
Al	14.8a,b	7.8	18.5c,d,e	13.5	8.0a,c,f	2.8	9.6d,g	2.7	34.8b,e,f,g	21.6
As	0.3a,b	0.2	0.4c	0.2	0.5	0.2	0.5a	0.2	0.6b,c	0.2
Caa	326.1a	7.6	326.7b	11.5	330.4	7.0	330.0	7.8	338.5a,b	14.1
Cd	0.018	0.011	0.015	0.005	0.014	0.014	0.012a	0.005	0.021a	0.007
Cr	1.5a	1.1	3.1a,b,c	1.9	2.3	1.0	1.6b	1.1	1.8c	1.2
Cu	0.5a	0.4	0.6b	0.5	0.6c	0.4	0.7d	0.6	1.4a,b,c,d	1.8
Fe	20.4a	11.6	27.1b	22.3	17.0c	5.8	17.8d	5.5	54.6a,b,c,d	31.9
Mg	2081a	231	1922	154	2018	248	2124b	312	1857a,b	222
Mn	1.1a	0.5	1.3b	0.7	2.2c	2.2	0.8c,d	0.2	2.3a,b,d	0.7
Mo	0.10	0.06	0.10	0.03	0.10	0.04	0.10	0.05	0.10	0.05
Ni	0.30a	0.04	0.30 b	0.03	0.20 c	0.03	0.20	0.03	0.20a,b,c	0.06
Pb	0.5	0.2	0.4	0.1	0.6	0.4	0.7	0.8	0.5	0.3
Sc	0.029a,b	0.008	0.032c,d,e	0.010	0.020c	0.011	0.014a,d	0.007	0.013b,d	0.010
Se	1.72	0.18	1.74	0.35	1.65	0.28	1.71	0.27	1.65	0.31
Sr	300a,b,c	55	220a	33	235b	52	242	36	243c	62
V	0.06a	0.05	0.10b	0.05	0.09c	0.04	0.08d	0.04	0.15a,b,c,d	0.06
Zn	35.5a,b,c,d	9.2	22.8a,e	15.5	13.3b,f	2.72	22.8c,f,g	6.80	11.9d,e,g	3.7

Values with lowercase letters are significant inter-colony differences (P < 0.05; HSD post hoc test, ANOVA of log- or log(x + 1)-transformed data)

SD standard deviation

^a×10³