I’ve cleaned this kind of mess on balcony chairs and patio cushions, and the key is to be gentle and quick. Bird poop is acidic and can set into the weave, so don’t let it dry if you can help it.
First, put on gloves. Remove solids with a plastic scraper, dull knife, or damp paper towel. Lift it away; don’t rub it into the fabric. Rinse the area with cool water—not hot—to dilute the mess. Hot water can set stains and sometimes affect dyes.
Mix a little mild dish soap or gentle laundry detergent with cool water. Use about a teaspoon per quart. Test on a hidden spot first, especially on dark or bright fabric. Apply the suds with a soft sponge or microfiber cloth. Let it sit 5–10 minutes. Then use a soft-bristled brush in light circles. Don’t use a stiff brush or pressure washer; both can abrade the fabric and make fading worse.
For leftover discoloration, try a fabric-safe enzyme cleaner made for outdoor cushions, or a color-safe oxygen bleach only if the care tag allows it. Avoid chlorine bleach, ammonia, and harsh solvents unless the manufacturer specifically says they’re safe. Rinse thoroughly with cool water until no soap remains. Soap residue can attract dirt and break down fabric treatments.
Blot with a clean towel, then air dry in the shade. Direct sun while wet can sometimes bake in residue and contribute to fading over time. If the cushion has a removable cover, follow its care tag: usually cold gentle wash, mild detergent, no chlorine bleach, and air dry. Don’t put foam inserts in the wash. Once everything is dry, reapply a fabric protector if the manufacturer recommends it. If the stain is old, repeat the gentle process rather than using stronger chemicals.