Results
There was no significant correlation between fuel stores and microbial killing ability (Table 1, Figure 1) or IgY levels (Table 2, Figure 1) in any of the four species. However, Julian day (date of capture) had a significant negative effect on microbial killing ability in Song thrushes and Wheatears (Figure 2, Table 1) and on IgY levels in Song thrushes (Figure 2, Table 2), meaning birds arriving at the stopover later in the migration season had lower microbial killing and lower IgY levels ability than birds arriving earlier. Microbial killing ability and IgY levels did not differ between sexes.
Table 1: The correlation test output between microbial killing ability and fuel stores, microbial killing ability and Julian day in four species of migrating birds during spring migration; and Wilcoxon test output for sex differences in microbial killing ability in four species during spring migration. P-values <0.05 are marked in bold.