Data from: Low intensity blood parasite infections do not reduce the aerobic performance of migratory birds

Blood parasites (Haemosporidia) are thought to impair the flight
performance of infected animals, and therefore, infected birds are
expected to differ from their non-infected counterparts in migratory
capacity. Since haemosporidians invade host erythrocytes, it is commonly
assumed that infected individuals will have compromised aerobic capacity,
but this has not been examined in free-living birds. We tested if
haemosporidian infections affect aerobic performance by examining
metabolic rates and exercise endurance in migratory great reed warblers
(Acrocephalus arundinaceus) experimentally treated with Plasmodium
relictum pGRW04 and in naturally infected wild birds over consecutive life
history stages. We found no effect of acute or chronic infections on
resting metabolic rate, maximum metabolic rate or exercise endurance in
either experimentally treated or free-living birds. Oxygen consumption
rates during rest and while undergoing maximum exercise as well as
exercise endurance increased from breeding to migration stages in both
infected and non-infected birds. Importantly, phenotypic changes
associated with preparation for migration were similarly unaffected by
parasitaemia. Consequently, migratory birds experiencing parasitaemia
levels typical of chronic infection do not differ in migratory capacity
from their uninfected counterparts. Thus, if infected hosts differ from
uninfected conspecifics in migration phenology, another mechanism than
changes in aerobic capacity should be involved.