The results from the Alaska Department of Fish and Game's necropsies on dead pigeons will be interesting. If salt is the cause of the lethargic behavior that renders the pigeons more vulnerable to predators, I hope the results will also give some indication why it's happening this year when it hasn't apparently been a problem before. Is there a new chemical compound in use? Are the pigeons unusually malnourished, so that the effect of the salt ingestion is more severe?
Regarding the "viciousness" of the ravens who are consuming some of the pigeons - they aren't being vicious. Food is scarcer in winter and the ravens have to compete for what's available. In the book "Ravens in Winter," raven researcher Bernd Heinrich reported on a number of studies that showed that ravens catch live prey. While rodents and birds may not be a large part of the diet of these opportunistic scavengers, Heinrich reported on ravens catching mice, young rabbits, and baby tortoises, as well as picking off sickly birds and other animals - and a northern harrier hawk that was placed in the same enclosure with a raven was reduced to feet and feathers by the following day.
Scavengers and predators play important roles in their ecosystems - when I look at the amount of plastic and packaging that encases most of the food we buy (not to mention nonfood items), I wish we were as efficient at "leaving no trace" as the rest of nature.