Energy expenditure during flight implicated in regulating OXY
depletion but not d-ROMs
Rate of energy expended during the flight (kJ/min) was not related to
levels of plasma oxidative damage (R2=0.12, Table S3;
Fig. 3A) but was related to the decrease in non-enzymatic antioxidant
capacity during the acute flight (R2= 0.39, Table S1;
Fig. 3B). Only a quarter of birds experienced increased d-ROM levels
during an acute flight suggesting that most birds employed a successful
antioxidant strategy to avoid the accumulation of d-ROMs at all energy
expenditures (Fig. 3A, note direction of arrow; S1C, note labels
indicating d-ROM levels). Energy consumption during the flight did not
explain AF levels of d-ROMs or the change in plasma d-ROMs during the
flight (AF-PF; Fig. 3A, Table S3; AF: T46 = -2.018, P =
0.050, Δ During Flight d-ROMs: T46 = -1.485, P = 0.149).
In contrast, OXY was lowest in birds that consumed more energy during
flight (Table S3; AF: T46 = -3.133, P = 0.003), and Δ
During Flight OXY decreased to the greatest extent in birds expending
more energy (Fig. 3B, Table S3; Δ During Flight OXY: T46= -2.821, P = 0.007). This relationship was primarily driven by 7
individuals that decreased OXY by an average of -128 mmol
l−1 of HClO neutralized (Fig. 3B and Fig. S1C), well
below the mean decrease (-22.7 ± 10.4 mmol l−1 of HClO
neutralized). These birds expended energy in the upper 50% range
(>0.51 kJ/min was consumed by the upper 50% of individuals)
(Fig. 3B and Fig. S1C), although other individuals that expended similar
amounts of energy during flight did not have such extreme decreases in
OXY. Instead, 5 of these birds increased uric acid by an average of 1.4
mmol, well above the mean increase (0.5 ± 0.06 mmol); whereas the
remaining birds did not change these circulating measures (OXY, uric
acid) from the averages.