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

J D Paruk,D Long,D C Evers,B J Sigel,E M Adams,I J Stenhouse,M Duron,J Hemming,P Tuttle,A T Gilbert,W A Montevecchi

doi:10.1007/s10661-019-7925-y

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.

Highlights

Seabirds are excellent indicators of oil pollution because they spend most of their time in marine environments on the ocean surface where oil tends to disperse and persist817 Page 2 of 9 after spills (Furness and Camphuysen 1997; Montevecchi 1993, 2001)
We focused on three target species that fit those criteria and that were relatively common and widespread: the American white pelican (Pelecanus erythrorhynchos), which tends to inhabit coastal waters (King and Michot 2002); the common loon (Gavia immer), which tends to inhabit nearshore waters (Jodice 1993; Kenow et al 2009); and the northern gannet (Morus bassanus), which inhabits both nearshore and offshore waters
Oil was observed on 16.9% (347/2050) of the assessed pelicans with most showing trace (83%, 289/347) or light (11%, 38/347) extents, and some with moderate oiling levels (6%, 20/347; Table 1)

Summary

Introduction

817 Page 2 of 9 after spills (Furness and Camphuysen 1997; Montevecchi 1993, 2001) They are at greater risk of oil exposure than other birds. Birds can ingest oil directly from the water, from their food, and from preening contaminated feathers (Burger 1997). Some estimates suggest that birds ingest 50% of the oil on their feathers within 8 h of exposure (Hartung and Hunt 1966). Ingestion of oil exposes birds to polycyclic aromatic hydrocarbons (PAHs), highly toxic components of crude oil and known carcinogens (Albers 2006). Exposure to sublethal oiling levels puts more birds at risk, potentially leading to lower fitness (Golet et al 2002; AlonsoAlvarez et al 2007)

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Results

Discussion

Conclusion