The influence of natural variation and organohalogenated contaminants on physiological parameters in white-tailed eagle (Haliaeetus albicilla) nestlings from Norway

A retrospective investigation of feather corticosterone in a highly contaminated white-tailed eagle (Haliaeetus albicilla) population

Exposure to persistent organic pollutants (POPs), such as organochlorines (OCs) and polybrominated diphenyl ethers (PBDEs), is associated with adverse health effects in wildlife. Many POPs have been banned and consequently their environmental concentrations have declined. To assess both temporal trends of POPs and their detrimental impacts, raptors are extensively used as biomonitors due to their high food web position and high contaminant levels. White-tailed eagles (WTEs; Haliaeetus albicilla) in the Baltic ecosystem represent a sentinel species of environmental pollution, as they have suffered population declines due to reproductive failure caused by severe exposure to dichlorodiphenyltrichloroethane (DDT) and polychlorinated biphenyls (PCB) during the 1960s through 1980s. However, there is a lack of long-term studies that cover a wide range of environmental contaminants and their effects at the individual level. In this study, we used 135 pooled samples of shed body feathers collected in 1968-2012 from breeding WTE pairs in Sweden. Feathers constitute a temporal archive for substances incorporated into the feather during growth, including corticosterone, which is the primary avian glucocorticoid and a stress-associated hormone. Here, we analysed the WTE feather pools to investigate annual variations in feather corticosterone (fCORT), POPs (OCs and PBDEs), and stable carbon and nitrogen isotopes (SIs; dietary proxies). We examined whether the expected fluctuations in POPs affected fCORT (8-94 pg. mm^-1) in the WTE pairs. Despite clear temporal declining trends in POP concentrations (p < 0.01), we found no significant associations between fCORT and POPs or SIs (p > 0.05 in all cases). Our results do not support fCORT as a relevant biomarker of contaminant-mediated effects in WTEs despite studying a highly contaminated population. However, although not detecting a relationship between fCORT, POP contamination and diet, fCORT represents a non-destructive and retrospective assessment of long-term stress physiology in wild raptors otherwise not readily available.

Feathers as an integrated measure of organohalogen contamination, its dietary sources and corticosterone in nestlings of a terrestrial bird of prey, the northern Goshawk (Accipiter gentilis)

In this study, we evaluated the suitability of body feathers, preen oil and plasma for estimation of organohalogen compound (OHC) exposure in northern goshawk Accipiter gentilis nestlings (n = 37; 14 nests). In addition, body feathers received further examination concerning their potential to provide an integrated assessment of (1) OHC exposure, (2) its dietary sources (carbon sources and trophic position) and (3) adrenal gland response (corticosterone). While tetrabromobisphenol A was not detected in any sample, the presence of polychlorinated biphenyls, organochlorine pesticides, polybrominated diphenyl ethers and hexabromocyclododecane in body feathers (median: 23, 19, 1.6 and 3.5 ng g^-1 respectively), plasma (median: 7.5, 6.2, 0.50 and 1.0 ng g^-1 ww, respectively) and preen oil (median: 750, 600, 18 and 9.57 ng g^-1 ww, respectively) suggests analytical suitability for biomonitoring of major OHCs in the three matrices. Furthermore, strong and significant associations (0.20 ≤ R² ≤ 0.98; all P < 0.05) among the OHC concentrations in all three tissues showed that body feathers and preen oil reliably reflect circulating plasma OHC levels. Of the dietary proxies, δ¹³C (carbon source) was the most suitable predictor for variation in feather OHCs concentrations, while no significant relationships between body feather OHCs and δ¹⁵N (trophic position) were found. Finally, body feather corticosterone concentrations were not related to variation in OHC concentrations. This is the first study to evaluate feathers of a terrestrial bird of prey as an integrated non-destructive tool to jointly assess nestling ecophysiology and ecotoxicology.

Influence of perfluoroalkyl acids and other parameters on circulating thyroid hormones and immune-related microRNA expression in free-ranging nestling peregrine falcons

Exposure to certain perfluoroalkyl acids (PFAAs) can have considerable effects on the endocrine and immune systems, although such effects remain largely uncharacterized in wildlife. Using an apex avian predator, we investigated possible relationships of thyroid hormones (THs), specifically free (F) and total (T) thyroxine (FT4; TT4) and triiodothyronine (FT3; TT3), and the expression of an immune-related microRNA biomarker (i.e., miR-155), with the concentrations of 11 PFAAs in nestling peregrine falcons (Falco peregrinus). Nestling peregrines (n = 56; usually two chicks of each sex per nest) were blood sampled when 23 ± 4 days old in urban and rural regions of the Laurentian Great Lakes Basin (Ontario, Canada) in 2016 and 2018. The circulating concentrations of several PFAAs were significantly associated with THs and estimated thyroid gland activity (TT3:TT4; FT3:FT4), including PFHxS (FT3; FT3:FT4), PFDS (TT3; TT3:TT4), PFOA (TT4; FT3:FT4), PFTeDA (TT4; FT3:FT4), PFHxDA (TT4; TT3:TT4) and ΣPFCAs (TT4). Our novel evaluation of miR-155 in peregrine nestlings identified significantly negative relationships of plasma miR-155 counts with PFHxS and PFOA concentrations, indicating potential down-regulation of miR-155 expression and impaired immunity. Several PFAA homologues significantly predicted the variation in THs and miR-155 in conjunction with year (e.g., inter-annual differences in weather, ambient temperature, rainfall), region (urban/rural), nestling age, and/or diet (trophic position; δ¹⁵N), which suggests that multiple environmental and biological stressors, including PFAA exposure, influenced thyroid activity and immune function in these nestlings. Further research is warranted to identify the mechanisms and additional impacts of PFAA-related thyroid and immune disruption on the growth, development, and health risks in developing birds.

Lead isotopic signatures in blood from incubating common eiders (Somateria mollissima) in the central Baltic Sea

The Christiansø colony of common eiders (Somateria mollissima) in the central Baltic Sea were exposed to high levels of Pb during the 2018 breeding season that were not present in 2017. Due to these high Pb blood levels, the present study investigated possible Pb sources and Pb dynamics within this vulnerable colony. We analyzed body mass and lead isotopic ratios (Pb-IRs) in blood taken from the same incubating eiders at the early (day 4) and late (day 24) stages of incubation during the 2018 breeding season (n = 23). Pb-IRs 208/207, 208/206, 206/207, and 207/206 were analyzed using high resolution inductively coupled mass spectrometry. We found largely similar Pb-IRs from the different stages of incubation indicating a predominantly constant endogenous source of Pb exposure. We suggest the increasing Pb levels come from pre-nesting and nesting foraging and from medullary bone release. The similar Pb-IRs also indicate continued metabolization of the medullary bone to meet the nutritional and energy demands of incubation. Comparisons to Pb-IR reports from the Baltic Sea showed multiple sources of pollution distinguished by a difference between Pb-IRs in individuals with Pb blood concentrations >500 μg/kg ww and <500 μg/kg ww. The most highly contaminated individuals in the present study had Pb-IRs similar to those of Pb ammunition indicating shot pellet uptake. This study further emphasizes the need for continued biomonitoring of the Christiansø colony, including fecal sampling and environmental field sampling to identify the origin and extent of dietary Pb exposure on Christiansø. As a representative unit of the Baltic Flyway population; the Christiansø colony provides an important opportunity for continued investigation into Pb contamination, population dynamics, and declines.

Plasma protein fractions in free-living white-tailed eagle (Haliaeetus albicilla) nestlings from Norway

BACKGROUND

Capillary electrophoresis of plasma proteins has shown great potential as a complementary diagnostic tool for avian species. However, reference intervals for plasma proteins are sparse or lacking for several free-living avian species. The current study reports electrophoretic patterns and concentrations of plasma proteins determined for 70 free-living white-tailed eagle (Haliaeetus albicilla) nestlings from two locations in Norway (Steigen and Smøla) in order to establish reference values for this subpopulation using capillary electrophoresis. The nestlings were between 44 and 87 days of age, and the plasma protein concentrations were investigated for age, sex, year (2015 and 2016) and location differences. To our knowledge, this is the first report of reference intervals of plasma proteins analysed by capillary electrophoresis in free-living white-tailed eagle nestlings.

RESULTS

The plasma protein concentrations (% of total protein, mean ± SE) were determined for prealbumin (13.7%, 4.34 ± 0.15 g/L), albumin (46.7%, 14.81 ± 0.24 g/L), α₁-globulin (2.4%, 0.74 ± 0.03 g/L), α₂-globulin (11.7%, 3.72 ± 0.06 g/L), β-globulin (15.9%, 5.06 ± 0.08 g/L) and γ-globulin (9.6%, 3.05 ± 0.09 g/L). Significant differences were found between the two locations for prealbumin, α₂- and γ-globulins. No significant differences were found between the two sampling years or sexes, and no effect of age was found for any of the plasma proteins. However, prealbumin levels were several folds higher than previously reported from adults of closely related birds of prey species. There were no other studies on capillary electrophoresis of nestling plasma available for comparison.

CONCLUSION

Significant differences were found between sampling locations for prealbumin, α₂- and γ-globulins, which may indicate differences in inflammatory or infectious status between nestlings at the two locations. Sampling year, sex or age had no significant effect on the plasma protein concentrations. These results provide novel data on plasma protein concentrations by capillary electrophoresis and may be useful for evaluation of health status in free-living white-tailed eagle nestlings.