Figure 1: Scatter plots of immune function and fuel stores in four bird species during spring migration. Panels 1-4 show the relationship between microbial killing ability (% E.coli killed) and fuel stores and panels 5-8 show the relationship between IgY levels (mOD/min) and fuel stores. Dashed lines indicate non-significant correlations. Please note that the x-axis is differently scaled among the figure panels.