. 2017 Jul 10;7:5014. doi: 10.1038/s41598-017-04575-y

Table 6.

Results from LM analysis of stable carbon and nitrogen isotope signatures (δ¹³C and δ¹⁵N), after backward selection.

Tissue	Response variable
Tissue	Explanatory variable	Estimate	Std. Error	t value	P value
Egg yolk	δ¹³C
	Intercept	−23.70	0.33	−71.25	<0.001
	Site	1.11	0.47	2.36	0.031
	δ¹⁵N
	Intercept	5.32	0.16	33.63	<0.001
	Site	−0.47	0.22	−2.12	0.050
Adult blood	δ¹³C
	Intercept	−25.90	0.16	−164.18	<0.001
	Site	0.36	0.08	4.79	<0.001
	δ¹⁵N
	Intercept	5.66	0.33	17.15	<0.001
Nestling blood	δ¹³C
	Intercept	−26.94	0.22	−124.54	<0.001
	Site	0.41	0.11	3.70	0.001
	δ¹⁵N
	Intercept	4.94	0.30	16.74	<0.001
	Site	0.54	0.15	3.58	0.001

Sampled tissues were eggs, and whole blood of adult and nestling blue tits. Initial explanatory variables were always site and date, and also sex for adult samples, and were dropped if not significant via backward selection (only significant variables are shown).