Figure 1.

Diet composition may affect immune function, body mass and moult directly (I, II & III). Immune indices, body mass and moult may covary (a, b and c) if diet affects all or any of immune function, body mass or moult with resultant effect on others. Diet effect may follow alternative indirect pathways: solid lines—diet affects immune index and immune index affects body mass and/or moult, or dashed lines—diet affects body mass, body mass affects immune index and/or moult, or dotdash lines—diet affect moult and moult affects body mass and/or immune index. Note however, that the hypothetical indirect effect of diet which arises from a direct effect on moult can only be tested reasonably in the moulting season, and so was not considered