The time to exhaustion increased over the experimental period from an average of 2.8 to 6.1 min in captive birds, but was not different between infected and non-infected cohorts (t = −0.42; figure 2; electronic supplementary material, table S1). In wild-caught individuals, the time to exhaustion also increased significantly over the three life-history stages (p < 0.01), averaging about 30% and 65% higher during post-breeding and migration, respectively, than during the late-breeding stages (figure 3). Endurance times of infected free-living birds did not differ from their parasite-free conspecifics during any period of measurement (low parasitaemia: t = 1.42, high parasitaemia: t = −0.91). Thus, birds in migratory disposition could sustain energy-demanding exercise for much longer than at earlier phases, irrespective of parasitaemia.