From this story in the Globe & Mail:
When David Hancock saw the bald-eagle count on the Chehalis River drop from more than 7,000 to fewer than 400 over a few days in December, he knew a crisis was coming. Earlier this week, news reports that starving eagles were "falling out of the sky" in the Comox Valley, on Vancouver Island, confirmed his fears. Wildlife rescue centres on the Island have reported birds growing so weak from hunger that they fall out of trees, or fly so clumsily they hit things. One crashed into a roof. Mr. Hancock said a collapse of chum salmon runs has left British Columbia's bald-eagle population without enough food to make it through the winter, leaving them weak from hunger and forcing thousands of birds to scavenge at garbage dumps.
_Mr. Hancock said about 25,000 eagles flock to salmon rivers in the Pacific Northwest in the fall, to feed on the carcasses of spawning salmon. One of the biggest gatherings is on the Chehalis River, about 100 kilometres east of Vancouver, where as many as 9,000 eagles gather in November and December, drawn by what is usually a large run of chum salmon. The big fish, which average about 6 kilograms, are among the last salmon to spawn and their carcasses are usually available on gravel bars well into the winter. But Mr. Hancock said the chum didn't arrive in any numbers on the Chehalis this year, reflecting a coast-wide collapse of the species, and then heavy rains washed away what carcasses there were. The birds were forced to disperse, to look for food where they could find it. "It was absolutely incredible. Within 10 days, we had gone from 7,200 eagles to 345 … So I knew it was going to be a pretty desperate winter," said Mr. Hancock, who has been studying eagles for 50 years. "So where did they go? I have a count of 1,387 one day at the Vancouver dump … that was in the week following the Chehalis dispersal," he said.