Investigation of exposure to radioactive contaminants to free-living birds

Investigation of direct and indirect effects of exposure to radioactive contaminants in free-living birds through analysis of feather corticosterone concentrations

This project will investigate the utility of quantifying feather corticosterone (CORTf), the major avian stress hormone, as a biomarker of chronic radiation exposure in a wild passerine bird species, the great tit (Parus major), within the Chernobyl exclusion zone (CEZ). Measures of CORTf will be determined in feathers sampled from known live birds, at specific locations within a gradient of radioactive contamination. In February 2017, 160 nest boxes (NBs) were deployed across sites selected within similar habitats, and across four sequentially increasing radioactive contamination levels. Biometric measurements and feather samples were taken from nestlings in the week immediately prior to fledging from May to June for analysis of corticosterone.

Feather samples taken were a matched pair of secondary feathers from either wing and a selection of 10 inter-scapular feathers (region between shoulder blades) to provide a consistent comparison of hormone levels in two feather types, and provide adequate sampling media for subsequent hormone extraction. Feathers will be assessed for viability as a minimally to non-invasive marker of radiation exposure in free-living passerine bird species.

As radiation levels are highly heterogeneous within and between sites, a sub-sample of nestlings were humanely euthanised from each NB to assess total whole body radionuclide activity of Cs-137 and Sr-90, providing an integral measure of radiation exposure which is essential to validate CORTf as a relevant biomarker of radiation exposure. Blood and muscle samples from euthanised subjects were taken for global DNA analysis in concert with the Institut de Radioprotection et de Sûreté Nucléaire (IRSN) in France. The IRSN will collaborate on a laboratory study involving exposure of zebra finches (Taeniopygia guttata) in a controlled environment to external radiation and assess the same biomarkers from wild birds within the CEZ as a comparison of field vs laboratory effects.

Field sampling in the CEZ will be repeated in 2018, with the NBs erected within the CEZ becoming part of a longer-term monitoring program into the direct and indirect effects of radioactive contaminants to wildlife.