This is especially true with the bold-patterned drakes. The saucy colors seem to leap out and beckon. Conversely, in gray light, fog or drizzle, ducks and geese may seem farther away than they really are. The imagined 50-yard shot often turns out to be closer to 35. As a rule of thumb in poor light, if ducks or geese are visible enough to identify by species and sex, they are more than close enough to kill.
Experience is the best aid in judging range.
If possible, try to establish some sort of range marker. You might pace the distance to a levee, or place a decoy at 40 yards or, among flooded timber, estimate the height of the closest trees. Such a gauge can prove helpful. This apparent contradiction can spare some flaming misses. Teal and scaup are the worst of the banzai chargers, and their diminutive size only compounds the problem.