For most folks, the Columbia River means salmon--salmon and sturgeon, salmon and steelhead, salmon and American shad. But to these guys the charms of the lower Columbia are its winter-scoured solitude, its mercurial and often menacing nature, and its massive populations of diving ducks, particularly bluebills. After a few hundred thousand pintails, wigeon, and greenwing teal migrate through the region, some 15,000 greater and lesser scaup spend the winter in the lower Columbia area. Unlike puddle ducks, divers such as scaup and canvasbacks swim underwater as they grub for mollusks and submerged vegetation. Stout-bodied birds with short wings and legs set near the tail, scaup mass in huge flocks and haunt open waters. They're widely figured as unwary (or outright dumb) and barely fit for the table. Out here, my hosts tell me, you either love big-river diver hunting or you hate it. And they're happy as thumbnail clams that 95 percent of local duck hunters fall into the latter category.