Date of Award

8-17-2024

Document Type

Thesis

Abstract

Pacific common eiders (Somateria mollissima v-nigrum; common eiders) are capital breeding seaducks that fast throughout their ~26 day incubation period. The incubation fast includes three metabolic phases: (I) a transition from feeding to using energy stored during the pre-breeding season, (II) the use of stored lipids for energy, and (III) the use of stored protein for energy as lipid reserves near depletion. With limited energy reserves for incubation, common eiders are more vulnerable to factors that increase the metabolic demands of reproduction, such as climate change or disturbance. We assessed the following metrics of body condition: mass, packed-cell volume, β-hydroxybutyrate, uric acid, and triacylglycerol, to estimate fasting phase of incubating common eiders. Our primary goal was to understand if common eiders breeding along the Beaufort Sea coast of Alaska entered phase III of fasting and, if so, at what point during incubation. We analyzed blood samples throughout incubation from 230 common eiders captured between Spy Island, west of Prudhoe Bay, and the U.S.-Canada Border from 2014 to 2019. Mass and packed-cell volume decreased throughout incubation which was expected as females lose up to 45% of their body mass while fasting. Serum β-hydroxybutyrate increased during incubation, indicating an increased use of stored lipids, typical during phase II of fasting. Serum uric acid decreased during incubation, also suggesting common eiders remained in phase II of fasting and were effective at protein sparing. On average, serum triacylglycerol initially decreased during incubation, consistent with phase II of fasting, then increased towards the end suggesting that some females may be feeding to augment the metabolic needs of incubation. Our body condition analysis suggests that the majority of common eiders breeding along the Beaufort Sea coast of Alaska are primarily using lipids for energy, sparing protein, and finishing incubation in phase II of fasting.

Handle

http://hdl.handle.net/11122/15548

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