We live in the Skyranch subdivision west of Jamestown. Since the deluge of September, we have not seen even one chickadee at our feeder. They used to be the prevalent bird. I posted this on our neighborhood qt, and someone at the Bar-K subdivision said that this is also the case at her feeder. Pygmy nuthatches are gone also. Did these birds get wiped out by the heavy rain? I have seen only one juvenile robin. Woodpeckers and jays are here.
Although there have been some reports of dead birds found following the floods in some Front Range communities, I doubt that the die-off of birds caused the decline of birds at your feeders.
The displacement, or regular fall movements, of just one or two families could make a big difference in what somebody sees at the feeder. The soaking and wind during that week probably brought down a lot of cavity branches and trunks. There is always a big influx of mountain chickadees to lower elevations, even the plains, every fall and winter. Harder to notice, but I bet major reshuffling of the cards happens with black-caps in September and October. Presence of birds at feeders sometimes indicates a shortage of something in the wild. Maybe all the rain made it such that the chickadees don't need the feeder as much (which would be a good thing). That false interpretation happens all the time with hummingbirds. Fewer hummers at feeders usually means there's a good flower bloom. In regard to birds, I think people tend to overestimate the effects of storms, fires, floods, and so on. Birds are much more adaptable than people. They have wings, marvelous survival instincts, and common sense.
These explanations are reinforced by the following Boulder Audubon article: http://www.audubonmagazine.org/articles/nature/how-colorado-flooding-affecting-birds-and-other-wildlife.