The fossil record of `` P. pervetus '' includes many complete skeletons from Green River Formation sites ( Early Eocene ) , suggesting that the birds nested in colonies and possibly were liable to succumb to botulism , similar to many colony-nesting waterfowl or shorebirds today .
The fossil record includes many complete skeletons from Green River Formation sites ( early Eocene ) . This suggests that the birds nested in colonies , similar to many colony-nesting waterfowl or shorebirds today .