The 2010 Deepwater Horizon disaster sent 4.9 million barrels of oil into the Gulf of Mexico over nearly three months, creating a slick at least 38,600 square miles in size. The amount was equivalent to more than 18 Exxon Valdez spills, yet the official tally of dead birds is only 2,121, or the number of carcasses classified as “visibly oiled” when they were collected.
Critics have maintained for years that the total is too low, even ridiculously so, and now the first comprehensive estimates of bird mortality caused by the spill suggest they may be right.
According to the estimates’ authors — Chris Haney, chief scientist with Defenders of Wildlife; Jeffrey Short, a marine chemist with the ocean-conservation group Oceana; and Harold Geiger, a scientist and former fisheries biologist with the Alaska Department of Fish and Game — 700,000 birds died within 25 miles of shore.
The estimate includes 260,000 Laughing Gulls, or 36 percent of the northern Gulf of Mexico population; 35,000 Northern Gannets (8 percent of the breeding population); 30,000 Royal Terns (15 percent); and 24,000 Brown Pelicans (12 percent).
The 1989 Exxon Valdez disaster, by contrast, killed about 300,000 birds.
The research was published online in May in Marine Ecology Progress Series, a journal of the Inter-Research Science Center in Germany.
A second study from the scientists will be published this summer. Estimating mortality of species found more than 25 miles from shore, it will say deaths among Band-rumped Storm-Petrel, Sooty Tern, and other seabirds totaled 120,000 individuals.
The authors focused on bird mortality due to acute oil exposure during the spring and summer of 2010, and they admit they did not account for oiled birds that continued to be found for at least a year after the spill. They also did not attempt to tally the deaths of rails, gallinules, and other birds found in marshes and other on-shore habitats that were heavily oiled.
Read the abstract
J. Christopher Haney, Harold J. Geiger, Jeffrey W. Short (2014). Acute bird mortality from the Deepwater Horizon MC 252 oil spill. II. Carcass sampling and exposure probability estimates for coastal Gulf of Mexico. Marine Ecology Progress Series, doi: 10.3354/meps10839. Abstract.
A version of this article appears in the August 2014 issue of BirdWatching. Subscribe.