Bird houses should be attractive to wild birds and homeowners alike. Excessive or improper painting of bird houses can severely reduce their appeal to potential inhabitants and endanger their health. Bird houses made from pine, cedar and cypress are well suited to sit in the elements without protection. Make sure they are not made from pressure-treated wood that contains harmful chemicals such as creosote, partial chromosome paint (PCP) and arsenic. When searching for the right paint or surface protectant for bird houses, never use anything that has lead as an ingredient.
Exterior Latex Paint
Latex paint is a water-soluble material containing acrylic resins and is one of the safest options for painting bird houses. Exterior latex paint should be applied in one or two coats, depending on the desired outcome. Paints can only be applied to the outside surface of bird houses. Birds peck at the inside of their homes, and paint chips -- even from relatively non-toxic latex -- should never be available inside bird houses.
Exterior Oil Paint
Oil paints have been used extensively for painting wood exposed to the elements because of their deeply penetrating and sealing properties. However, oil paints continuously dry, eventually becoming dry and brittle. This makes them generally unsafe for bird houses. Some oil-based exterior paints have an animal-safety rating, and asking your paint distributor about an individual paint's properties can help to inform your decision.
Water-based polyurethanes supply a clear plastic coating to the outside of bird houses. This maintains the original look of the wood while protecting it against the elements and water damage. Water-based polyurethane is safer to use than oil-based polyurethane due to oil's volatility. Polyurethane is available in matt, semigloss and high-gloss finishes.
Varnishes and shellacs produce a finish similar to polyurethane. Marine-grade oil-based varnishes are a highly effective sealant for wooden bird houses. Marine-grade varnishes are meant for high-traffic boat walkways and wooden structures and will provide years of protection. Tinted varnishes can be used to give the bird house's wood a different colour. Oil-based varnishes can be applied with a brush and require white spirit or turpentine to clean.
Next to natural and non-pressure treated wood, natural oils and waxes are the safest options for painting bird houses. Linseed oil provides a protective barrier against the elements and can be reapplied easily. Use a rag or sponge to rub the oil directly into the raw or sanded wood. Beeswax is also an effective sealant. It can be rubbed into the unfinished wood in multiple coats and then buffed with a clean, tight-weave rag to give it a glossy, waterproof surface.