 As waterbirds that feed on fish , pelicans are highly susceptible to oil spills , both directly by being oiled and by the impact on their food resources . A 2007 report to the California Fish and Game Commission estimated that , during the previous 20 years , some 500 – 1000 brown pelicans had been affected by oil spills in California . A 2011 report by the Center for Biological Diversity , a year after the April 2010 Deepwater Horizon oil spill , said that 932 brown pelicans had been collected after being affected by oiling and estimated that ten times that number had been harmed as a result of the spill . 
