This is just a suggestion from a non-scientist. Consider that many birds swallow rocks to help in grinding up food and helping digestion. Since we are talking about the seas where there are not many rocks, even on the islands, perhaps these birds are deliberately using the plastics as replacement for rocks. I doubt that the birds are stupid enough to mistake colored plastic for food...but they might see them as a substitute for rocks...which means that there really is nothing strange about this. The plastic caps often have ridged edges and could actually be good substitutes for rocks given the environment at sea. The assumption that this plastic kills them may actually be a result of our prejudice against ourselves that we are evil for creating plastic. Pictures don't always tell the full story and environmental scientists often jump to conclusions about the effect of technology upon the world. I'm just saying this may not be as bad as the alarmists are making it out to be. Besides, since Teddy Roosevelt, the US government was supposed to be there to protect these birds. Why aren't they doing it if this is such a bad problem?