Table 2 General Linear Models (GLM) and model terms describing the relationship between liver metal(loid) concentration and age, mass of ingested plastic items / number of ingested plastic items and species. Models with a difference (Δ) in AIC of < 2 are considered equivalent models, and this table shows only models within 2 AIC of the best model (except Cd, where models within 3 AIC are shown). A ‘ + ’ sign denotes inclusion of the categorical variable in the model. Pachytila seabirds; fairy prion (n = 26) and slender-billed prion (n = 25) were collected dead in emaciated condition during a “seabird wreck”, New Zealand 2016.

Metal	Intercept	Age	Mass plastic items	# plastic items	Species	R²	df	LogLik	AICc	Δ	Wgt
Al AIC null = 853.4	936.5	+				0.11	4	− 417.5	843.9	0	0.24
	439.3					0	2	− 420.5	845.2	1.3	0.12
	1008.6	+		− 45.57		0.13	5	− 416.9	845.2	1.3	0.12
	521.8			− 53.97		0.03	3	− 419.7	845.9	2	0.09
Mn AIC null = 517.8	31	+				0.11	4	− 240.3	489.5	0	0.24
	25.1					0	2	− 243.3	490.9	1.5	0.12
	27.8			− 1.76		0.03	3	− 242.5	491.5	2	0.09
	32.4	+		− 0.91		0.12	5	− 240.1	491.5	2	0.09
Fe AIC null = 1018	4580.5	+				0.09	4	− 482	972.8	0	0.18
	4004.3					0	2	− 484.4	973.1	0.3	0.15
	4329			− 212.31		0.04	3	− 483.4	973.4	0.6	0.13
	4158		− 6.38			0.02	3	− 484	974.5	1.7	0.07
	3909.5	+			+	0.1	5	− 481.6	974.6	1.8	0.07
	4783.1	+		− 127.99		0.1	5	− 481.6	974.6	1.8	0.07
Co AIC null = 167.9	0.8	+				0.1	4	− 70.4	149.6	0	0.19
	0.9				+	0.05	3	− 71.8	150.2	0.6	0.14
	0.7					0	2	− 73.1	150.5	0.9	0.12
	0.8			− 0.06		0.03	3	− 72.4	151.3	1.8	0.08
Cu AIC null = 530.6	36.8				+	0.07	3	− 207.3	421.2	0	0.27
	40.5					0	2	− 209.1	422.5	1.4	0.14
	39			0.97		0.04	3	− 208.1	422.8	1.6	0.12
	36.6			0.53	+	0.08	4	− 207.1	423	1.8	0.11
Zn AIC null = 725.4	226				+	0.21	3	− 302.7	612	0	0.43
Zn AIC null = 725.4	224.4			4.51	+	0.22	4	− 302.3	613.5	1.4	0.21
Cd AIC null = 565.2	27.8				+	0.2	3	− 255.2	516.9	0	0.49
	28		− 0.03		+	0.2	4	− 255.1	519.1	2.2	0.16
	27.8			− 0.04	+	0.2	4	− 255.2	519.2	2.4	0.15

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