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Getting the best Barn Owl nestbox for your site
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Let's say you have a piece of land in mind and you are thinking of providing a nestbox for Barn Owls. What type of box would be best? Should you go for a box in a building, in a tree, or on a pole? The success of your nestbox will depend to a large extent on making the right choice so here's a brief guide...
If there's a large building that a Barn Owl can enter at 3+ metres (10') above the ground then this is almost certainly the best place to put the new nestbox. Boxes in buildings are easier to erect*, cheaper to obtain (cheaper and quicker to make), they last a lot longer, and the extra shelter afforded by the building will benefit the owls. If there's a building with no access, can a small owl hole be made? Mounting a box on the outside of a building is an option but it has many disadvantages and cutting holes in timber, asbestos* sheet, metal sheet, or even knocking a hole through a brick or block-built wall is not as hard as you may think*. Buildings that are in human or agricultural use are usually very suitable as Barn Owls can get used to almost any kind of activity as long as they can stay out of sight.
If there's no building at least 3 metres high or none accessible by Barn Owls then a tree box is generally the next-best option. Tree boxes are more expensive to obtain and more difficult to erect* than indoor boxes, they don't last as long, and the owls won't have much shelter. There's also a greater chance of occupation by some other species. However, (provided that you have a suitable tree in a suitable position) they are a much more practical option than a pole box.
Pole boxes are the least preferred option. They are by far the most expensive (because they are larger and more time-consuming to build), they are the hardest to erect*, they don't last anything like as long as boxes in buildings, and the owls are completely exposed to the elements. Many pole boxes are also very unsafe for emerging young owls. After its first flight (or fall), any fledgling owl that is unable to fly back up to the box stands little chance of survival. The only major advantage of the pole box is that it can be provided almost anywhere (you are not dependant on there being a suitable building or tree on-site). The poles need to be very substantial and generally need to be erected by machine - the costs are considerable. Pole boxes are only cost effective where there is good foraging habitat but no suitable buildings or trees for boxes to be placed in. The Barn Owl Trusts new Pole-box design maximises nest safety for the emerging young.
* Before creating an entrance hole or erecting a box, please ensure that you have properly assessed the risks involved, particlarly with regard to cutting asbestos and working at height.
Nestboxes that have the nest place and entrance hole on the same level allow owlets to fall out easily and owlets that are not in the nest generally starve to death or are taken by foxes. Some types of tree box have a low entrance hole and these are only useful if erected WITHIN THE BRANCHES of a suitable tree. In this way owlets are less likely to fall to the ground and any that do stand a good chance of being able to climb back in. Nestboxes with a drop of less then 25cm (10") from the bottom of the hole to the bottom of the box are not much better than all-on-one-level boxes. In 2008 we decided to stop using (and stop providing information on) Barn Owl nestboxes with low entrance holes. They are just not safe enough.
It was way back in 1997 that the Barn Owl Trust produced its first "deep nestbox design" for use in buildings (see "Nestboxes for use in barns..." >). This has a drop of 46cm (18") from the bottom of the hole to the nest level. Out of 238 recorded cases of owlets falling from nestboxes 75% were from the old-style all-on-one-level boxes and only 4% were from deep boxes. In 2006 the Barn Owl Trust, in association with The Nestbox Company, designed a deep tree box suitable for mounting on the side of a tree trunk. The design allows owlets to easily climb from the box into the tree and back into the box again - a great improvement over the "A-frame" type tree boxes that some people use. Since 2006 we've made further improvements to our tree nestbox design. (See "Nestboxes for use on trees" >).
In 2008 the Trust produced an all-new deep Pole Box design with an exercise platform for the emerging owlets that goes all the way around the box! Early trials suggest that this is far better than earlier versions or low-entrance-hole types.
We have also designed a small stone building as a refuge for Barn Owls and other species (as featured on the Channel 4 programme Wild Thing I Love You). We hope to produce detailed plans of this innovative 'wildlife refuge'. In the meantime it's illustrated within its own webpage. Follow the link >
If you're thinking of building-in a space for Barn Owls within the apex of a roof (such as a barn conversion) rather than erecting a pre-made box, check out other pages on the website >
P.S. Don't forget that the owl's food supply has a MASSIVE influence on occupation, survival and breeding success. Check out our pages on the creation and management of optimum habitat - rough tussocky grassland with a permanent litter-layer...
There is a lot more information on this topic in the Barn Owl Conservation Handbook