Diving adaptations of migratory seabirds: oxygen stores in Procellariiformes highlight a key role for pectoral myoglobin levels in determining dive behaviour

Procellariiform (tube nosed) seabirds have impressive dive/flight capabilities yet the physiological mechanisms underpinning their dive performance remain poorly described. We compared dive capacity traits (total oxygen stores, theoretical aerobic dive limit ( t ADL) and muscle buffering capacities) in three species of Procellariiformes breeding in northern New Zealand (36°53’13”S, 174°26’12”E) during the 2014/2015 season. Species examined spanned a range of underwater foraging behaviour, i.e., grey-faced petrel ( Pterodroma gouldi, x̄ dive depth: 1.6 m ), flesh-footed shearwater ( Ardenna carneipes , x̄ dive depth: 3.5 m) and the sooty shearwater ( Ardenna grisea , x̄ mean depth: 6.9 m). Our results show that the deeper and longer diving shearwaters have significantly greater total oxygen stores than grey-faced petrels i.e., 41.0 ± 3.1, 46.2 ± 2.3 and 48.6 ± 2.2 mL O ₂ kg ^-1 for grey-faced petrels, sooty shearwaters and flesh-footed respectively, which mirrored respective theoretical aerobic dive limit ( t ADL) times (44.2 ± 3.4, 49.6 ± 2.7 and 52.3 ± 2.4 seconds). In addition, dive logger data indicates that these species rarely exceed t ADL. When compared across flying/diving seabirds, myoglobin concentrations in pectoral muscles correlated strongly with dive duration, indicating the role of these muscles in seabird diving. This myoglobin oxygen supply appears sufficient to suppress metabolic acidosis as muscle buffering capacity of flight muscles did not differ among species. Lastly, distinct temporal differences in haematological parameters suggest a plasticity in blood oxygen stores among years. Nonetheless, our results show the degree to which physiological adaptations meet function, with Procellariiformes exhibiting traits matching observations of their underwater performance.