Cleaning Bird Poop From Your Car: The Acidic Nightmare

bird poop on car

It looks harmless enough, if not rather disgusting, driving along when a big splat of bird poop splatters all over the hood of your car. It looks terrible but you just drive through it not knowing how aggressive that powerful organic acid is when reacting chemically with your automotive paint. If you did, you would rush to the first available carwash!

What’s Involved with Bird Dung?

Birds (and reptiles) excrete ammonia and urine from the bloodstream in the form of uric acid crystals that look like white paste. Like a hungry beast, this caustic ammonium hydroxide, when exposed to alkali metal, immediately begins to eat away at the paint, a chemical process that quickens with exposure to high temperatures and when exposed to moisture like dew, rain, or humidity. The damage is slower acting in temperatures under 40°F, but if your vehicle sits out in the hot summer sun, the damage is exacerbated.

Nearly 100 percent insoluble in water, anyone who has ever washed a car with bird droppings on the surface has noticed how difficult it is to wash off. Heated by the sun, your urethane clear coat softens and expands to solidify the bird excrement on the paint surface, penetrating the paint matrix. The longer the droppings remain, the harder it becomes to remove them. The result is scars, or indentations, in the clear coat that we call etchings.

Etching is the most common flaw caused by this degradation, but paint discoloration, bubbling, and swelling around the affected area is also possible. Waxes and sealants are not acid proof so they provide only short-term protection, but they do act like a sacrificial layer between the uric acid and your paint. You should still wash off bird droppings as soon as possible, and continue to reapply waxes and/or sealants.

Keep These Things in Mind:

  • Avoid using a quick detailer (QD) spray to remove bird excrement since they contain polymers or wax that seal the acid in, rather than removing it.

  • Do not use plain water. Uric acid is nearly 100% water insoluble.

  • Do not get in a hurry. Take your time to do it correctly.

  • Remove bird droppings as soon as possible. The longer you leave it, moisture and heat reactivates the chemical process.

Identify the Problem

Etching is not the only problems caused by environmental contaminants like bird droppings. Oxidation, which is a buildup of contaminants that causes cloudiness on your surface, is the result of digested insects, seeds, and berries, which are very acidic, especially when excreted onto your vehicle.

Identify whether the damage is etching, or oxidation caused by the urethane clear coat expanding under a hot sun, thereby encapsulating contaminants. You can verify the surface condition by looking through a 30X magnifier.

Correcting the Problem

Remember that moisture and heat re-activate the acid, so use non-abrasive products first, to dissolve or remove the acidic contaminants. Never scrub dried bird doo. Birds use abrasives to digest their food consisting of bones from their prey, sand, grit, and even small gravel that when excreted causes scratches. The following recommendations will soften dry excrement:

  1. Use an Insect Remover that is made to combat acidic messes
  2. If the droppings have softened enough, a microfiber towel is sufficient. However, if it’s a little stubborn then a bug sponge would likely be very effective.
  3. If those don’t work, then use a paint cleaner for a more aggressive approach.

To dissolve the surface etching:

  1. Clay the surface and polish
  2. Likelihood is you’ll need to correct the whole panel so that you don’t get a noticeable shiny spot.

Paint Protection

This brings us to the importance of paint protection not just from the most common dangers of the sun and against dents and dings, but also from environmental contaminants like bird poop. Most automotive clear coats are hydrophobic, that is, they repel water, dirt, and other contaminants, but unless you polish your vehicle on a regular basis to remove oxidation, bird droppings and other contaminants will still bond to the paint surface.

Waxes and polymer sealants are little protection against bird droppings, but they keep the surface hydrophobic, which prevents them from bonding to the paint and making it easier to remove them.

Bird droppings may seem innocuous, but if given a choice between you and the roof of a car, bird poop will ravish your paint first!


Photo by Bob Cotter (Flickr)