Oiling of American white pelicans, common loons, and northern gannets in the winter following the Deepwater Horizon (MC252) oil spill

Abstract

The Natural Resource Damage Assessment and Restoration Trustees for the Deepwater Horizon oil spill assessed the external oiling of migratory bird species dependent on open water in the Gulf of Mexico following the aforementioned spill. The assessment was designed to evaluate birds that use open water during the winter within 40 km of the Gulf shoreline. We focused on the American white pelican (Pelecanus erythrorhynchos), common loon (Gavia immer), and northern gannet (Morus bassanus). Point counts (pelican, loon) or strip transects (gannet) were used and each target species was assessed for oiling (unoiled, trace, light, moderate, or heavy amounts) and photographed. Due to distance at sighting and/or poor visibility, not all visible birds were assessed. The percentage of birds oiled varied by species, with the common loon being the highest (23.6%), followed by American white pelican (16.9%), and northern gannet (6.9%). Most of the American white pelicans and common loons had trace (83% and 72%, respectively) or light levels (11% and 24%, respectively) of oiling. The northern gannet had just trace levels of oiling. Some pelicans (6%) and loons (4%) had moderate amounts of oiling. Based on expert derived-mortality estimates and our estimates of oil exposure, we used Monte Carlo simulations to predict expected decreases of 2.5%, 4%, and 11% in the observed population for the northern gannet, American white pelican, and common loon, respectively. While these values are underestimates of the true values given the long time lag (10-12 months) between the oil spill and the assessment, these data represent some of the few estimates of exposure for these species and describe minimum risk estimates to these species. Keywords American white pelican. Common loon. Deepwater horizon oil spill. Northern gannet. Oiling

Migration patterns and wintering distribution of common loons breeding in the Upper Midwest

“…Several contributing factors have been attributed to mortality in common loons in marine environments including emaciation, food limitation, net entanglement, oiling associated with spills, contaminants, biotoxin exposure (e.g. botulism, ‘red tide'), parasitic infection, fungal infection and trauma (Alexander 1991, Spitzer 1995, Forrester et al 1997, Daoust et al 1998, Sidor et al 2003, Benjamins et al 2008, Starr et al 2017, Paruk et al 2019). Parasitic infection was the most prevalent contributing cause of mortality identified among juvenile loon carcasses recovered in this study.…”

“…Potential exposure of loons to petroleum or oil dispersants either directly or via prey ingestion is of concern, as these contaminants could possibly have negative effects on the productivity of affected birds. Paruk et al (2019) reported evidence of oiling among 23.6% of 1148 common loons examined in the GOM in the first winter following the 2010 Deepwater Horizon oil spill, and estimated mortality at 10.7% (based on the degree of oiling) among the loons assessed. Petroleum oil exposure has been linked to increased stress and reduced breeding success through altered breeding behavior and impaired egg formation and laying in birds (Fry 1995).…”

Antibacterial and anatomical defenses in an oil contaminated, vulnerable seaduck

“…Later in the laboratory, bodies and wing feathers were inspected visually for oil contamination as reflected by the feathers being sticky with a wet and shiny appearance rather than smooth and dry. Visual inspection of the plumage has been used to assess whether birds are contaminated with oil (Joensen, 1972 ; Paruk et al., 2019 ). The method has been recommended or used by the Trilateral Monitoring and Assessment Program for the Wadden Sea, by OSPAR, the Oslo‐Paris Commission, by US Wildlife Service and in Greenland in monitoring programs of oiled seabirds washed ashore (Berg, 2005 ; Camphuysen, 2005 ; Schulz et al., 2017 ; Wegeberg et al., 2017 ).…”

Estimating the numbers of aquatic birds affected by oil spills: pre-planning, response, and post-incident considerations

“…Haney et al (2017) noted the application of UV fluorescence to detect trace oiling of in-hand birds during the Deepwater Horizon. Paruk et al (2019) used digital photographs to categorize the degree of oiling for three species (Common Loons, American White Pelicans [Pelecanus erythrorhynchos], and Northern Gannets) post Deepwater Horizon and extrapolated impacts to populations.…”