I dunno how many hundred thousand miles of oil and gas pipelines there are in the US. Spill-type leaks are a rarity. The pipelines have automatic shutdowns for pressure drops.
The volume of spillage is low. Maybe cover an acre or three? Not enough to hurt any bird population beyond the occasional ground-nesting sort's nest. Far more birds are lost to wind generators and TV/radio towers.
But the nationwide total of "all of the above" is much less than what feral cats do in each and every individual state.
You're from BATFE? Come right in! I use all your fine products!