Demographic trends of Brown Pelicans in Louisiana before and after the Deepwater Horizon oil spill

Abstract

ABSTRACT. Marine oil spills may have extensive and deleterious effects on coastal waterbirds, but pre-spill data sets are often not available for making comparisons of demographics to the period following a spill. The 2010 Deepwater Horizon oil spill allowed us to compare Brown Pelican (Pelecanus occidentalis) demographics during pre-and post-spill years. We banded 1114 pelicans on Louisiana barrier islands from 2007 to 2009, tracked their distribution via band re-sighting surveys from 2008 to 2011, and conducted age-structure surveys. Across Louisiana coastal islands in 2011, we detected 7% of pelicans that had been oiled during the 2010 spill and released following rehabilitation. Similarly, 6% of pelicans (not oiled) banded at the same release site in 2007 were observed across coastal islands 1 yr after banding. We observed variation in proportions of pelicans that were 1, 2, and 3 or more years old among years (2008)(2009)(2010)(2011) and across islands, but little variation could readily be assigned to spill-related mortality. These Brown Pelican demographic trends one year following the Deepwater Horizon oil spill are contrary to other assessments of the impacts of oil contamination on marine birds. However, additional research is required to evaluate potential long-term population trends. RESUMEN. Las tendencias demográficas del Pelicano pardo, antes y después del derrame de petróleo Deepwater HorizonLos derrames de petróleo en el mar pueden tener amplios y efectos perjudiciales sobre las aves acuáticas en las zonas costeras, pero frecuentemente los conjuntos de datos que se refieren al tiempo antes del derrame no están disponibles para hacer comparaciones demográficas con el periodo que sigue el derrame. En el 2010, el derrame de petróleo Deepwater Horizon nos ha permitido comparar la demografía del Pelicano pardo (Pelecanus occidentalis) durante los años, antes y después, del derrame. Entre el 2007 al 2009, colocamos anillos en 1114 pelicanos en las islas de barrera en Luisiana. Luego hemos rastreado la distribución de estos pelicanos a través de re-estudios de avistamiento desde el 2008 al 2011, y realizamos encuestas demográficas sobre la estructura de la edad. En las islas costeras de Luisiana en el 2011, detectamos el 7% de pelicanos que habían sido empetrolados durante el derrame en el 2010, pero que fueron llevados a rehabilitación y liberados cuando terminaron su recuperación. Del mismo modo, el 6% de los pelicanos (no empetrolados) que fueron anillados en el mismo lugar de liberación (en el 2007) fueron observados en las islas costeras, un año después de ser anillados. Observamos variaciones en los porcentajes de pelicanos que tenían uno, dos, tres o más años de edad, entre los anos (2008 -2011) y a través de las islas. Poca variación podría ser asignada a la mortalidad relacionada con el derrame de petróleo. Estos estudios demográficos sobre el Pelicano pardo, hechos un año después del derrame de petróleo Deepwater Horizon, son contrarias a otras evaluaciones sobre los impactos de la contaminaci...

Effects of Pollution on Marine Organisms

“…Using both a carcass sampling model and an exposure probability model, Haney et al (2014b) calculated that approximately 700,000 birds died in the coastal GOM as a result of the Deepwater Horizon oil spill, but the numbers may be as low as 320,000 and as high as 1,900,000 within the 95% uncertainty bounds. Walter et al (2014) and pulmonary consolidation as well as mortality rates higher than previously recorded. A critique and reply followed publication.…”

Environmental effects of the Deepwater Horizon oil spill: A review

“…The study was criticized by Sackmann and Becker (2015) who suggested that an underestimating of carcass transport probability to shorelines was leading to overestimation of bird deaths by an order of magnitude; a comment which was refuted in a response letter from Haney et al (2015). Walter et al (2014) assessed the demographic trends of brown pelicans in LA before and after the DWH spill by banding 1114 individuals on LA barrier islands from 2007 to 2009 and tracking their distribution via band re-sighting surveys from 2008 to 2011. The study found little age-variation within the population that could readily be assigned to spill-related mortality, which was contrary to expectations.…”

Genetic structure of brown pelicans (Pelecanus occidentalis) in the northern Gulf of Mexico in the context of human management and disturbance

“…A study of Louisiana colonies over forty years suggested that when conditions at a colony site deteriorate, birds may move en masse to another site [ 82 ]. Several Louisiana colonies are known to have experienced severe physical degradation as a result of the spill [ 30 , 99 ] and persistent exposure to oil and oil-based compounds in subsequent years [ 100 ]. The degradation of high-quality nesting sites could have played a large role in dispersal of individuals from the area, resulting in increased gene flow between some, but not all pairs of populations.…”

“…The species has since established new nesting colonies in Louisiana [ 44 ], and its global population has grown to levels sufficient for its removal from the Endangered Species list in 2009 [ 45 ], but the degree to which Louisiana populations may have experienced genetic bottlenecks, particularly those associated with reintroduction, remains unclear. Additionally, the Deepwater Horizon oil spill in the year following delisting had immediate negative impacts on seabird and wading bird populations in the northern Gulf of Mexico, including brown pelicans [ 29 , 30 ]. These impacts include acute and direct mortality, as well as sub-lethal effects on behavior and condition, but as with most taxa the magnitude and nature of spill-related impacts for brown pelicans remain unclear.…”