Transfer of veterinary parasiticides from the fur lining bird’s nest to eggs and chicks

Previously we have found that spot-on insecticides commonly applied to dogs and cats to deter ticks and fleas contaminate lining of great tit and blue tit nests via birds using fur to line their nests. Here we describe significant positive correlations between pesticide concentrations found in the nest lining fur and those in unhatched eggs and dead chicks from the same nests, indicating that these compounds transfer from contaminated nesting material into avian tissues. This study advances our understanding of how environmental contamination from domestic sources may directly impact wildlife health and development. It highlights the need for improved environmental risk assessment for veterinary products intended for use on companion animals, and more specifically the need to determine whether the exposure we identify lead to impacts on bird health in the short or long term.