What are the primary effects of oil on birds?

Question

The primary problem involves physical alteration of the feather structure. When oiled, feathers lose their ability to trap air and repel water. As a result, birds can no longer maintain body heat; they become hypothermic; and their need for food increases. At the same time, due to oil on their plumage, birds do not float well; their swimming and foraging ability decreases; and they often cannot fly and will haul out of the water.

Answer 1

You answered your own question.  The ultimate result is that it kills them due to the effects that you mentioned.  For examples, you can do searches for Exxon Valdez and oil spill.

Answer 2

I think you have answered your own question my friend.

Answer 3

well pretty much what you just mentioned effects birds

Answer 4

Many oils contain toxic chemicals like benzene, and crude oils may contain that and much more like metals.  Assuming the bird survies the oil the toxic shock of the chemical exposure will surely affect the bird sooner or later.