One of the most puzzling aspects of bird feeding is how poorly designed most feeders are. It is not uncommon at all to hear folks complaining about refill rates, sometimes multiple times per day. When factoring the cost of good quality seed, this can become very expensive. Fortunately, just sifting through the ground "waste" (usually full of whole, uneaten seed) may provide the clues needed to remedy the situation.
Most commercially available feeders are designed to bring the seed level up and even with the station edge (tube) or trough edge (hopper). That, or with little raised edge to spare. This results in seed falling out even with the tidiest of native birds eating. House Sparrows and Starlings accelerate the problem, by deliberately throwing seed overboard thus emptying these feeders in a fraction of the time. Good design goes a long way toward reducing this.
When choosing your feeder, don't be afraid to ask for a seed fill-up demo to verify that waste is minimized. In the case of a tube, you can easily examine this by looking at the station roof trailing edge. You want to ensure that it comes down at least even with the station edge itself. If it does not, it is likely that the seed will come up too high and readily spill out. The below photos more than illustrate this problem:
In summary, avoid any feeder where the fill line of the station edge(s) isn't at least 1/8" lower, otherwise your bird seed will not stay in the feeder even under normal feeding conditions.