After the Deepwater Horizon oil rig blew out in the Gulf of Mexico some 50 miles from the nearest land, responders were left to cope with a search area of nearly 40,000 square miles, as well as wind and currents that kept evidence of damage away from the more easily searchable coastline.

Patrollers recovered fewer than 3,000 dead birds. But some had suspected that many more were unaccounted for.

Now a team of scientists has tried to quantify the extent of damage inflicted on the gulf’s bird population from the oil spill caused by the explosion. Based on models using publicly available data, the studies estimated that about 800,000 birds died in coastal and offshore waters.

“Part of the reason they discovered so few carcasses is because the oceanographic currents for the most part moved them away,” said Jeffrey Short, a marine chemist and a co-author of the studies.