Does melanin-based plumage coloration reflect health status of free-living birds in urban environments?

Table.4 Comparison between generalized linear model (GLM) and generalized additive model (GAM) testing the effects of plumage melanic coloration levels on the variation of monocyte and granulocyte numbers in infected Feral Pigeons (Columba livia) in urban environments

Numbers of monocytes ~ melanic-based coloration
Coefficient	Est.	SE	t-value	P	Sig.
Gaussian GLM with identity link (AIC = 187.93, ΔAIC = 0.67)
Intercept	7.10	1.566	4.53	< 0.001	***
MBC	0.03	0.041	0.75	0.459	ns
GAM (Deviance explained = 8.13%, AIC = 187.26, ΔAIC = 0)
Intercept	8.03	0.929	8.65	< 0.001	***
Smooth term	edf	Ref. df	F	P	Sig.
Smooth (MBC)	1.64	2.03	0.83	0.458	ns

Numbers of granulocytes ~ melanic-based coloration
Coefficient	Est.	SE	t-value	P	Sig.
Gaussian GLM with identity link (AIC = 235.58, ΔAIC = 0.73)
Intercept	18.10	3.465	5.22	< 0.001	***
MBC	0.01	0.091	0.10	0.925	ns
GAM (Deviance explained = 6.22%, AIC = 234.85, ΔAIC = 0)
Intercept	18.37	2.055	8.94	< 0.001	***
Smooth term	edf	Ref. df	F	P	Sig.
Smooth (MBC)	1.59	1.97	0.54	0.582	ns

AIC Akaike’s information criterion, ΔAIC difference between the AICs of the tested model compared to the model with the best fit, Est. estimate, SE standard error, P probability value, Sig. statistical significance, ***P < 0.001, ns: P > 0.05, Edf estimated degrees of freedom, Ref. df: reference degrees of freedom, F: F-statistics

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