Ecological and spatial factors drive intra- and interspecific variation in exposure of subarctic predatory bird nestlings to persistent organic pollutants

Top predators in northern ecosystems may suffer from exposure to persistent organic pollutants (POPs) as this
exposure may synergistically interact with already elevated natural stress in these ecosystems. In the present
study, we aimed at identifying biological (sex, body condition), ecological (dietary carbon source, trophic
level) and spatial factors (local habitat, regional nest location) that may influence intra- and interspecific variation
in exposure of subarctic predatory bird nestlings to polychlorinated biphenyl 153 (CB 153), polybrominated
diphenyl ether 47 (BDE 47), dichlorodiphenyldichloroethylene (p,p′-DDE) and hexachlorobenzene (HCB). During
three breeding seasons (2008–2010), we sampled body feathers from fully-grown nestlings of three ecologically
distinct predatory bird species in subarctic Norway: Northern Goshawk (Accipiter gentilis), White-tailed
Eagle (Haliaeetus albicilla) and Golden Eagle (Aquila chrysaetos). The present study analysed, for the first time,
body feathers for both POPs and carbon (δ13C) and nitrogen (δ15N) stable isotopes, thus integrating the dietary
carbon source, trophic level and POP exposure for the larger part of the nestling stage.
Intraspecific variation in exposure was driven by a combination of ecological and spatial factors, often different
for individual compounds. In addition, combinations for individual compounds differed among species.
Trophic level and local habitat were the predominant predictors for CB 153, p,p′-DDE and BDE 47, indicating
their biomagnification and decreasing levels according to coast > fjord > inland. Variation in exposure may
also have been driven by inter-annual variation arisen from primary sources (e.g. p,p′-DDE) and/or possible
revolatilisation from secondary sources (e.g. HCB). Interspecific differences in POP exposure were best
explained by a combination of trophic level (biomagnification), dietary carbon source (food chain discrimination)
and regional nest location (historical POP contamination).
In conclusion, the combined analysis of POPs and stable isotopes in body feathers from fully-grown nestlings
has identified ecological and spatial factors that may drive POP exposure over the larger part of the nestling
stage. This methodological approach further promotes the promising use of nestling predatory bird body
feathers as a non-destructive sampling strategy to integrate various toxicological and ecological proxies
δ13C,δ15N,body feather,biomagnification, habitat,stable isotope