Fig. 4

Relationship between plumage melanic-based coloration and number of infected erythrocytes in free-living Feral Pigeons (Columba livia) in urban environments of Algeria. The dashed red line is a linear regression with a Poisson GLM fit, with 95% confidence region in light grey. The blue solid line represents the predicted curve from a generalized additive model (GAM) with Poisson error distribution. Solid white circles within side boxplots indicate the average (sample size = 30 individuals)