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:
Above/below: Avian Woodlink Series feeders (white) are correctly designed. It is clear in these photos that the station roof trailing edge comes down even with the station edge itself. The result is seed staying in the feeder, with birds having to reach in that little bit further to access. Debris (husks, in this case) and some dropped seeds are contained by the tray below, giving it a second chance among platform-friendly birds e.g. Cardinals.
Above: A closer look at the Woodlink. The seed (in this case Black Oil Sunflower) is well contained in the station and will not spill out on its own. This is what you want to look for when selecting a feeder. Ask for a seed fill demo if necessary, but a look at the station roof line is usually enough.
Above/below: An inexpensive tube feeder purchased at Lowes. The above (and below, with Safflower) are exactly what you
don't want in a feeder design, which accounts for most store-bought models unfortunately. You can literally empty these feeders with barely shaking them. During normal feeding, multiple seeds fall out for each one taken and eaten. The ground below your setup will quickly accumulate whole seed, and unless you have hoards of ground feeding birds, it may start to germinate -- probably by Spring.
Above: A closer up look at the Lowes no-name brand feeder, this time with Safflower. This is a 100% terrible design. The station roof trailing edge is split, and makes it only halfway to the station edge itself. If we were to use millet-types seeds which have lower viscosity, this feeder will literally empty itself sitting still.
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.
