Birds keep pooping on my patio. What’s the best way to clean it?

Q: I recently had a flagstone patio installed in my backyard. I love the patio, but I also love having my bird feeder, so the flagstones are covered with bird poop. I routinely take down the feeder at dusk and then hose the pavers, but that doesn’t always remove the stains. Any recommendations, other than taking down the bird feeder?

A: Birds don’t have separate systems for eliminating solid and liquid waste, like we do. With a few exceptions - hummingbirds being one - it all comes out in one sticky, acidic substance that dries hard. The droppings make a real mess on a patio near a feeder or on a deck overhung by trees where birds perch. If the birds have been feeding on berries, the droppings can be red or purple, and if they land on awnings or outdoor furniture cushions, they can stain just like fresh berry juice. When the poop lands on a car, droppings can etch the clear coat on paint and leave the surface looking dull.

It was long thought that uric acid was what made bird poop white and so difficult to remove, because uric acid crystals are white and don’t easily dissolve in water. Many websites still blame uric acid for the issues with bird poop, but research published in the Journal of Ornithology in 2020 found that while birds do produce uric acid as a water-thrifty way to eliminate nitrogen waste, bacteria in their guts apparently convert it before the birds excrete it. The study found bird droppings contain only breakdown products: ammonium urate, struvite and two unknown compounds. Ammonium urate, found in fertilizer and explosives, is a white crystal, and struvite, which is found in some kidney stones, can also be white.

Whatever the precise chemical composition, bird poop can be a pain to clean up, especially if you don’t get to it right away. Some solutions work most of the time, but not always, probably because all bird poop isn’t the same. It varies by the kind of birds, their diet and whether the droppings are fresh or dried. But in all cases, the deposits are easier to remove when they are still gooey. Also true: If you’re dealing with a delicate surface, rinsing off the crud is safer than rubbing it off because bird poop often contains sand. In lieu of teeth, birds use grit in their gizzards to grind up food.

When bird droppings build up into a caked-on mess inches deep, a proper cleanup can look like a hazardous-waste scene, complete with workers in protective clothing and full-face respirators. Large quantities of bird poop are indeed classified as hazardous or infectious waste in many areas because birds can carry dozens of diseases, and their dried deposits can contain spores of fungal diseases that infect humans. Large cleanup jobs are probably best left to pros, or at least to homeowners who follow all the precautions and don’t suffer from respiratory problems. Wetting down the deposits before scraping them off is key, as is protecting yourself from inhaling any dust and disposing of the waste as local hazardous-waste rules require.

But a typical cleanup around a home doesn’t involve shoveling off waste, just washing it off. That isn’t especially dangerous as long as you follow basic safety precautions, such as wearing rubber gloves if you need to touch the deposits or rinse water and eye protection in case of splashes. On patios, decks and many other surfaces, simply hosing off the surface with water squirted through a spray nozzle is often enough. If everything doesn’t come off, pick up a broom and use it as a no-stooping-required scrub brush, then rinse again. Or add a little hand dishwashing detergent to a bucket of hot water and dip the broom into that before you scrub.

Water, soap and elbow grease provide all the cleaning power needed at the Sylvan Heights Bird Park, which cares for 5,000 birds in Scotland Neck, North Carolina, said Ali Lubbock, one of the founders. “We just wash everything down,” she said. For especially tenacious droppings - she singled out pigeon poop - they first scrape off any dry clumps, then wet everything down. “Put on rubber gloves and scrub,” she said. When you finish and take off the gloves, wash your hands, using soap and water.

Another common tip is to add white vinegar to the wash water, at concentrations as high as half vinegar and half water. Vinegar, though, should be used with caution, especially if you rely on it frequently. It can etch some composite decking, concrete patios, and some stone pavers and flagstones, especially if they are sandstone or limestone. But vinegar is fine to use on wood decks or fences. And a little vinegar in soapy water is a good way to get bird deposits out of acrylic fabrics, which are often found in awnings and outdoor cushions. Sunbrella, which makes these fabrics, recommends mixing a teaspoon of dishwashing liquid and a teaspoon of white vinegar with a cup of water. Or, for a larger batch, you could mix a gallon of water and one-third cup each of the soap and vinegar.

Where bird droppings are especially frequent and don’t rinse off easily, investing in specialty cleaners may make sense. Poop-Off Bird Poop Remover contains enzymes and detergent and is designed to quickly soften deposits on surfaces like cages and fabrics so they wash off easily. The manufacturer also makes Poop-Off Outdoor Multi-Use Cleaner. That comes with a cap that connects to a hose and automatically sprays the right proportion of cleaner and water on patios, decks, boats and many other outdoor surfaces. Cory Gellerstedt, president of Nixalite, which sells a range of pest bird and wildlife control products, said it works better than anything he’s found to soften dried droppings so they hose off completely. “I use it all the time,” he said.

If the droppings are on a car, especially one with a clear coat or shiny paint, a cleaner such as Meguiar’s Ultimate Quik Detailer can help remove deposits without the risk of creating a dull spot. Washing the car is the best way to remove bird droppings, a customer-care representative for the company said, but when a vehicle is basically clean except for bird droppings, using the detailer is a quick and easy way to remove the droppings before they damage the finish. The product contains silicone polymers to enhance shine, so while it can be used on surfaces other than cars, including plastic parts, it’s not a good option for a matte surface, where a shiny patch might stand out even more than the remnants of a stubborn bird deposit.