We followed the same experimental protocols throughout all metabolic measurements: (i) we placed birds in holding cages with access to water but no food for 3 h before starting the RMR measurements, (ii) we then placed them in respirometers within a constant-temperature cabinet and measured RMR overnight, (iii) birds were returned to holding cages the next morning and given free access to food and water for about 3–4 h, (iv) we then measured their MMR and, lastly (v) we took a blood sample at completion of MMR to determine each bird's infection status, parasitaemia and haemoglobin concentration.