Crested auklets (Aethia cristatella) are one of the most abundant planktivorous seabirds that breed on the islands of the Bering Sea. I hypothesized that the brilliant yellow-orange pigment of this bird’s accessory bill plates could be informative about the animal’s physiology and ecology. I collected samples and observations at breeding colonies. I performed experiments and assays in combination with UV-Vis spectrophotometry to test hypotheses concerning the pigment molecule(s) and potential functions. Extracts of the bill pigment had maximum UV-Vis absorbance (248 nm) similar to pterins, important antioxidants and metabolites. The absorbance spectra of the bill pigment overlapped with favored prey of crested auklets, euphausiids (Thysanoessa spp.). All of the samples were prepared in 0.1 M NaOH. Reaction of the bill pigment in concentrated sulfuric acid revealed spectra consistent with pentacyclic triterpenoids, phytochemicals that occur in marine phytoplankton.
Results/Conclusions
These results suggest markers of lower trophic levels and their metabolites may occur in the bill pigment of crested auklets. The crested auklet’s bill pigment had a second band of absorption at (230 nm), and a similar band of absorption was evident in plasma (235 nm). In a TBARS (thiobarbituric acid reactive substances) assay, malondialdehyde (MDA) was negatively correlated (rs(0.05)2,25 = - 0.42, p < 0.05) with relative pigment concentration in plasma (235 nm). This suggests that the pigment molecules have a physiological role in circulating blood. This would be consistent with the antioxidant function of pterins. Observations from field research showed that crested auklets differ in the intensity of pigment expression in their accessory bill plates. Intensity of bill reflectance (measured at 593 nm) correlated negatively with wing chord (r0.05(2)13 = -0.71, p<0.01) in breeding adult crested auklets at Little Diomede I., AK in 2016. In this same population, 11% of crested auklets captured (n=82) had blackened culmens. This stage of pigment acquisition was characteristic of late April, based on a phenological study of pigment acquisition in a captive population. Multiple indicators showed 2016 was a stressful breeding season, possibly attributable to additive effects of increased ocean heat. Crested auklets specialize on euphausiids and large oceanic copepods, but those prey may have been less available in 2016. Stable isotope analysis (δ13C, δ15N) showed a shift in consumption patterns among crested auklets compared to 2015. Results confirm my working hypothesis that the bill pigment is traceable in the food web and is related to animal health.