Brown pelican (Pelecanus occidentalis) population viability faces perennial risk due to hurricanes, breeding habitat loss, and contamination from oil spills. To assess factors that may influence demographic processes and colony success, and to evaluate techniques that could ameliorate population threats, we conducted research on 11 islands in Louisiana, USA. From 2007 to 2011 we banded 1500 chicks, monitored their distribution and survival probabilities, compared age class proportions across years, and evaluated reproductive success in relation to breeding site conditions. We found that pelicans express strong philopatry and that neither sex nor age influenced their island use patterns. However, low band re-sighting proportions suggest numerous individuals either perished or emigrated.
In 2008, Hurricanes Gustav and Ike caused differing degrees of habitat degradation to some of our colony islands. At one colony that experienced extensive shoreline retreat and loss of preferred nesting habitat, it appears that storm effects may have reduced survival of banded birds, elicited their movement outside our study region, and reduced nest success. In 2010, the Deepwater Horizon oil spill contaminated many of our study islands. We observed a notable decrease in nest success during the year of the spill compared to previous years. However, similar proportions of pelicans one, two, and three or more years old from 2008 to 2011 across islands exposed to oil suggest that there was not an age-biased effect due to possible contamination.
In an attempt to promote additional nesting colonies that can mitigate threats to concentrated breeding populations, we performed translocations and used decoys to attract breeding adults to un-colonized islands. Although our efforts over three years adhered to commonly successful practices, we did not detect any pelicans that expressed nesting behavior with either technique. Despite the 2009 removal of the brown pelican from the Endangered Species List, the species remains susceptible to threats of habitat loss and environmental contamination. We identified several factors that promote nest and colony success, and also conditions that educe colony abandonment. Brown pelican conservation could benefit by diminishing the deleterious factors we identified, and promoting island restoration and protection at successful colony sites.
|Adviser||Paul L. Leberg|
|School||UNIVERSITY OF LOUISIANA AT LAFAYETTE|
|Subjects||Ecology; Conservation biology|
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