Bird feathers as a non-invasive method for ecotoxicological monitoring; a rapid review

Abstract

The decline in animal population with resulting risk of eventual disruption of ecosystem functioning has necessitated moves towards non-invasive sampling methods for ecotoxicological studies. These efforts have focused on developing sampling methodologies geared towards prioritizing conservation of biodiversity. Using a rapid review approach, 106 articles covering peer-reviewed studies, theses, and manuscripts under peer-review quantifying contaminants in feathers were examined. Meta-analysis of extracted information (n=91) revealed that most studies on feather contaminants originate from Europe (47.6 %) and Asia (32.9%), with a higher occurrence of such studies between 2015 and 2020. The most utilized feather-type across studies were body feathers (28.6%) and tail feathers (20%). Majority of the studies (60.5%) used feathers alone to estimate contaminant exposure and uptake; 14.8% used feathers and blood, while 12.3% used feathers and soft tissues (liver, kidney, muscle etc.). Inferences from the review reveal that feathers as a non-invasive sampling method provide advantages by having contaminant concentrations that are relatable with internal organs of birds, captures information on ambient contaminant concentrations based on exogenous contributions and application for historic studies. However, some available data indicate that selective uptake of some metals in organs of species could significantly reduce the number of contaminants stored in feathers and may limit its accuracy for biomonitoring. Furthermore, the different degrees of external deposition of persistent organic contaminants (PCBs, PBDEs, etc) onto the feather surface due to differential degradability/metabolization may limit the use of feathers to estimate exogenous effects. Nonetheless, while feathers have been used successfully as a non-invasive method for ecotoxicological monitoring of metals, metalloids and organic pollutants, knowledge on bird ontogeny and contaminant-specific trends in feathers could improve the accuracy of monitoring. Further efforts towards broadening the impact and advancement of this field method in future studies of avian research especially in developing countries is recommended.