Fig. 2

Final model based on training data and model validation results for mass (a), tarsus (b), culmen 2015 (c), and culmen 2016–2017 (d). For each panel, gray points are the training data used for model training. Purple points are the test data (actual ages), while the green points are the ages predicted from the final model. The predicted age from the model is connected to the actual age by the vertical black lines. The black lines are the regression lines and are linear for mass and tarsus and quadratic for both culmen measurements. Shaded blue areas represent the 95% confidence intervals. In all four panels, points are jittered to see the spread of the data