The number of eared grebes rescued - and killed - after their Monday crash-landings at the U.S. Army's Dugway Proving Ground was far higher than originally estimated.

Wildlife biologists and volunteers spent Monday and Tuesday gathering 12,800 water birds, carrying the 7,828 surviving birds by pickup trucks to ponds in the region.

The birds were migrating back to the Great Salt Lake for the summer, but apparently became disoriented by snow and fog and mistook wet roads and parking lots for water. Built for water, with legs far to the back of their bodies, they can lift off from the ground only with great difficulty.

An estimated 100 birds were taken to rehabilitation facilities, Dugway spokeswoman Paula Thomas said.

Biologists working under a permit from the U.S. Fish and Wildlife Service were burning and burying the birds that died or were so seriously injured they had to be euthanized.