Figure 4.

Test of priming method. Fly-specific IgY antibodies increased significantly in birds exposed to flies for 2 weeks compared to birds that were previously unexposed to flies (t-test, P < 0.001, see text for further statistical details). Asterisk indicates significant difference with P < 0.05. All birds were fitted with backpacks (Figure 2), half of the backpacks had ten uninfected flies to “prime” the anti-fly immune response; the other half did not have any flies.