Flexibility of exercise capacity during nestling feeding in blue tits

The study was carried out in Southern Sweden in a nest box population of
blue tits (Cyanistes caeruleus). We measured the maximum exercise-induced
metabolic rate (MMR), endurance, and pre- and post- exercise resting
metabolic rate (RMRpre and RMRpost) of male blue tits both early on and at
the peak of the nestling feeding (day 5 and day 14). We compared blue tits
with enlarged and control brood sizes. We also measured nestling
biometrics and feeding frequency.