Fish oil disrupts seabird feather microstructure and waterproofing

Seabirds and other aquatic avifauna are highly sensitive to exposure to petroleum oils. A small amount of oil is sufficient to break down the feather barrier that is necessary to prevent water penetration and hypothermia. Far less attention has been paid to potential effects on aquatic birds of so called ‘edible oils’, non-petroleum oils such as vegetable and fish oils. In response to a sardine oil discharge by a vessel off the coast of British Columbia, we conducted an experiment to assess if feather exposure to sheens of sardine oil (ranging from 0.04 to 3μm in thickness) resulted in measurable oil and water uptake and significant feather microstructure disruption. We designed the experiment based on a previous experiment on effects of petroleum oils on seabird feathers. Feathers exposed to the thinnest fish oil sheens (0.04μm) resulted in measurable feather weight gain (from oil and water uptake) and significant feather microstructure disruption. Both feather weight gain and microstructure disruption increased with increasing fish oil thickness. Because of the absence of primary research on effects of edible oils on sea birds, we conducted interviews with wildlife rehabilitation professionals with experience rehabilitating sea birds after edible oil exposure. The consensus from interviews and our experiment indicated that physical contact with fish and other ‘edible oils’ in the marine environment is at least as harmful to seabirds as petroleum oils. •Little is known about effects of fish and other edible oils on seabirds.•We conducted lab experiments and interviewed wildlife response experts.•Lab experiments showed fish oil significantly disrupted feather microstructure.•Feathers exposed to fish oil absorbed water and oil indicating loss of waterproofing.•Experts agreed that fish oil is harmful to seabirds and requires intervention.