The attack of birds is far more subtle than that portrayed in Hitchcock’s film ‘The Birds’ in 1963. Incredibly acidic seabird guano spread liberally over boats’ sails, dodgers, biminis, rails and decks. That mix of fish fat and calcium from fish bones is worse than any glue – even if you are able to wash most of it from fibreglass, once it is dried, the residue can only be sanded back.
Once the sun and salt has completed the chemical process it seems to harden into a resin that only the most energetic actions or those involving chemicals can remove. After even just 2 or 3 weeks the boat becomes a stinking mess and a full days work to clean up. Sometimes it appears your boat will be singled out for carpet bombing over a shorter period of time as flocks of gulls choose it as their preferred meeting place or for target practice.
As someone who has worked in a boatyard cleaning bird mess from boats, I can certainly vouch to the severity of this problem. Bird guano is extremely acidic and very hard to remove once it has repeatedly dried in sunlight and wetted in seasalt. It is even harder to remove from covers than it is from wood or fibreglass as it discolours all types of covering fabric. A high-pressure hose is essential for a first clean and it is a bit more effective if you leave the bird mess to soak in warm water and cleaning solutions for a while first. If you have a steam cleaner this helps but be careful not to crack bits of the boat with heat.
After that it is a hard scrub with a soapy scrubbing brush and some proprietary boat cleaning products (unless you use ‘Chine Shine’ GRP cleaner, available from, you guessed it – OSM Boats). You may need a pack of plastic pan scourers too. If these don’t cut through the mess you might need to sand, chemically strip or wire-wool back to the surface.
Once you have got your boat clean, invest in a Gullsweep® Bird scarer to prevent the mess and keep the critters off your boat. Here is a picture of it in operation. It is called Gullsweep® and it is available by mail order from Outboard Services Ltd.
