Seed and feathers escape a bird cage for mechanical reasons, which is good news, because mechanical problems have mechanical fixes. Birds hull seed and flick the husks, flap showers of feather dust and down out through the bars, and splash bath water that floats debris onto the floor. You will not stop any of that, and should not try; hulling, flapping, and bathing are healthy behaviour. Instead, build a containment zone around the cage so the mess lands in one washable, sweepable area and stays there, then keep the zone honest with a routine measured in minutes.
Catch it at the cage first
The highest-return fix sits on the cage itself. Fit a mesh seed catcher or fabric skirt around the lower third of the cage, where hulling happens at the cups and most husks drop; it funnels debris back into the base tray instead of letting it parachute outward. Swap open cups at the bars for a hooded feeder or an enclosed feeding station mounted inside the cage, so the flick-and-hull action happens over the floor grate rather than at the room's edge. Site the bath inside the cage over the tray for the same reason. Line the base tray with paper you can lift out daily, rolled toward the middle so the day's husks and feathers leave in one parcel instead of shedding across the room on the way to the bin.
Then catch what escapes, on one mat
Even a well-skirted cage sheds feather dust and the odd determined husk, so define the zone on the floor: a low-pile, washable mat or a sheet of smooth flooring protector extending well beyond the cage footprint, largest on the side where you open the door and change cups. Keep the cage in a corner if you can, because two walls halve the directions mess can travel and make the mat's job easier. Vacuum or shake the mat outside on a short cycle, and wash it properly when feather dust builds in its surface, since old dust ground into a mat becomes the thing you were trying to avoid. Keep shoes and trailing curtains out of the zone; husks travel house-wide mostly by hitching on feet and fabric.
Habits that keep the zone small
Feed the mess-prone foods, spray millet, leafy greens, soft foods, at a single station inside the cage rather than clipped at various bars, so one spot takes the fallout. Time out-of-cage sessions to a play stand placed on its own tray or mat, because a bird preening happily on top of a bookcase seeds a room a cage skirt cannot protect. Sweep or hand-vacuum the zone daily, briefly, before debris gets walked outward, and do the wider room weekly. Store the broom and spare tray papers in the zone itself; a tidy-up that requires fetching equipment from another room is a tidy-up that gets skipped.
Containment that still lets the bird be a bird
Do not fix mess by shrinking the bird's life: never solve hulling by moving to an all-pellet fussiness or by taking away bathing, and do not wrap a cage so tightly in covers and skirts that airflow and light suffer. Check that skirts sit below the main perches and do not block your view of droppings on the tray paper, because that daily glance at the paper is also a health check you do not want to lose. If mess suddenly worsens, look for a cause, a moult, a new seed mix with lighter husks, a bath moved to the bars, before buying more gadgets. Dividing the daily tray change, mat sweep and weekly deep clean in KinsLe Care Teams keeps the bird corner contained as a shared habit, not one person's endless chore.