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Plastic Barn Owl Nest Boxes Versus Wooden: A Clear Choice

The molded plastic heat resistant Barn Owl Box is now being used by thousands of farms and properties.

In 2009, I was a field researcher and animal trainer for the Pittsburgh Zoo. In conjunction with Moraine Preservation Fund, we had erected over 200 wooden nest boxes in PA; however an inspection a few years later revealed many of them were rotting. The immense amount of work seemed wasted and no one had the money to build and erect replacements.

At that time I also spoke to the sustainable director for a large farming concern in Florida that had used barn owl boxes. He informed me they had given up using them since the weather quickly destroyed their plywood boxes. Similar stories came out of California. Few farms were employing large numbers of boxes, though many had a few. It seemed short-lived wooden boxes were deterring barn owl box programs.

So, over a two year period, I designed the plastic box. The product took off rapidly and we began to see large orders from vineyards and orchards. We also receive repeat orders from wildlife departments of various states. My guess had proven true: when farmers and property owners were offered a nest box that would last, they were more inclined to buy and erect them.

My goal of both conserving the barn owl and reducing the use of poisons seemed realized. To date, we have increased the number of nest boxes in the country by many thousands and this has had a positive impact on barn owl populations. Illinois alone has reported a five fold

Plastic nest boxes fledge large numbers of young

increase in their population. The Florida farms that had discontinued using wooden boxes have now installed over 1000 plastic boxes to controthe large numbers of cotton rats in their fields; they report 100% occupancy.

Our own study in Elk Grove California in 2012 attracted 18 breeding pairs that fledged 66 young on a scant 100 acre vineyard in a single season.

Occupation rate was 75%. The density of barn owls on that parcel of land was one of the highest ever reported. (Browning, et al. 2016 published by 27^th Vertebrate Pest Conference, University of CA Davis.)

Wooden boxes are increasingly being taken over by honey bees

Increasingly we have been receiving evidence of another benefit to plastic barn owl boxes. People with both wooden and plastic nest boxes have been noticing that only their wooden boxes have been invaded by honey bees. (And many such hives are Africanized strains of the bee that are highly aggressive and dangerous to humans.)

Our best guess is that the smooth, impregnable plastic surface does not allow the bees to glue their nest to the walls or ceilings. Honey bees will attack the nest, kill the young, and soon make the nest box uninhabitable except for themselves. And Africanized bees are moving northward. In California they have expanded their range since the 1990’s as far north as Napa County. We still urge caution when inspecting our nest boxes, but so far we have no reports of bee occupation.

Today, the choice remains between wood and plastic, and there is some debate over which may have advantages over the other. As someone who has used many of each in the field, I first want to say that both wooden and plastic boxes attract barn owls in high numbers where barn owl populations are good. That said, here are the pros and cons of each:

Pros and Cons between Wooden and Plastic Barn Owl Boxes

The Wooden Box

Advantages:

Can be built at home by do-it-yourselfers
Initial outlay is lower
Just as likely to attract barn owls as plastic

Disadvantages

Deteriorate in as little as two years
Need repainted periodically
If not repainted frequently, the wood surface makes the barn owl box too hot for fledglings
Harbor greater loads of parasites
Are heavy to install, requiring two people minimum.
Need replaced periodically, erasing the initial savings in costs.
To save on expense, many wooden boxes are built too small
Wooden boxes are frequently occupied by honey bees and these are often Africanized bees which present a danger to humans

The Plastic Barn Owl Nest Box

Advantages

Far outlasts wooden boxes
More economical overall
Never needs repainted
With heat reflective pigments, double box system, and efficient venting, remains cool in full sun
Larger size than most wooden boxes (26 x 17 x 17).
Achieves high rates of occupancy and fledgling success
Can be quickly installed by a single person
Evidence indicates that honey bees (including Africanized strains) do not build nests in plastic boxes due to not being able to glue their nests to the smooth plastic

Conclusion

There is nothing wrong with providing wooden boxes for barn owls. They may be particularly useful for do-it-yourselfers and beginners. But for farms and property owners who want to create reliably long-lasting nest box programs that require very little maintenance, plastic next boxes provide a clear choice.

Please go to www.barnowlbox.com for more info.

How and Why to Add Bedding to Barn Owl Nest Boxes

It seems that almost every aspect of maintaining barn owl nest boxes generates differing opinions; and how and why to add substrate to nest boxes is no exception.

One source of confusion comes from the fact that barn owls, unlike most birds, do not carry any bedding to their nests. On the surface, this would indicate that they do not need humans to add substrate to their nest boxes. Adding to the confusion is that barn owls do cough up pellets of fur and bone that accumulate on the floor of a nest. This also leads people to believe that these pellets negate the need for any additional nesting material. But there are some very good reasons to not rely on pellets for substrate.

Eggs are best protected by thick substrate.

For millennia, barn owls have nested in tree cavities. Such cavities had floors of soft, uneven wood and generally provided a fairly stable surface for the eggs to remain in place. But wooden and plastic nest boxes such as ours have hard, smooth floors and eggs roll readily around on such surfaces. Also, as the hen moves around, she can damage the eggs accidentally. Installing a nest box and not providing substrate means that when the hen begins laying, most of the floor will be bare and therefore dangerous to the eggs. Relying on pellet production is also not a good idea since the hen will produce only one or two pellets in the nest box per day. That is not enough to provide ample bedding to protect the eggs by the time the hen begins laying.

So, the answer is that three to four inches of bedding should be strewn across the entire floor of the nest box. Fine material such as laboratory bedding, sawdust, ground corn cob, or shredded wood should be avoided. The reason for this is that when the hen tears apart prey to feed to the youngest chicks, pieces of fine bedding can stick to the prey and then be ingested by the chick. Therefore, large pieced mulch such as garden mulch is perfect. This can be hardwood, pine, fir, or many other types of wood. Cedar is best avoided because it emits irritating fumes.

One year, my team of researchers in California could not re-bed our 25 nest boxes on our study vineyard in time for the beginning of breeding season. When we finally did get the opportunity, we found that most of the nest boxes that had eggs in them already also were ones that still contained a good amount of bedding. And nest boxes that had mostly bare floors did not–indicating that hens had rejected these nest boxes in favor of those that had a good amount of substrate. So, the barn owls themselves proved the point.