Start by dealing with it sooner rather than later. Bird poop is acidic and full of uric acid, and once it bakes into outdoor fabric—especially in a hot city courtyard or on a sunny balcony—it can leave a ghost mark or weaken the fibers. Put on disposable gloves, grab a paper towel and a plastic bag, and keep kids and pets away. Use a paper towel or a dull plastic scraper to lift off the solids; don’t press them into the weave. Throw the waste in the bag.
Before any cleaner touches the stain, check the care label and spot-test a hidden area. Outdoor furniture fabric varies a lot: solution-dyed acrylic, olefin, polyester, canvas, and coated fabrics all behave differently. Mix a little mild dish soap with lukewarm water—not hot—and test for color change or water rings. If the cushion has foam inside, keep water to a minimum; you don’t want a soggy cushion that mildews. For removable covers, follow the label; if you’re unsure, hand-wash rather than machine wash.
Apply the soapy water with a soft cloth or sponge. Blot and lift the stain, and don’t scrub aggressively. Work from the outside of the stain inward so you don’t spread it. Let the cleaner sit for a minute or two, then rinse by blotting with a clean damp cloth. Repeat with clean water until no soap remains, because residue can attract dirt. For stubborn dried bits, re-wet them with a damp cloth for about 10 minutes, then gently lift them away. An enzyme cleaner labeled safe for outdoor fabric can help with organic residue, but test it first. Diluted white vinegar can help with odor, but test it too, since acids can affect some finishes. Skip bleach, harsh solvents, melamine sponges, wire brushes, and pressure washers.
Dry the furniture upright in a shaded, well-ventilated spot, and use a fan if needed. Avoid direct high heat or a dryer unless the care label says otherwise. Once the fabric is fully dry, brush it gently with a soft brush if the nap feels flattened. If you normally use a manufacturer-approved fabric protector, reapply it after the fabric is completely dry. If the stain remains or the fabric is delicate or coated, contact the furniture maker or a professional cleaner rather than trying another strong product.