BARN OWL NESTING BOXES
The preferred “natural” nest sites of Barn Owls include hollows in high trees, tall rural buildings (old and new), rock crevices & holes in cliffs and though Barn Owls like their privacy, successful boxes can be sited near to quite busy locations such as farmyards. ln all cases, however, the predominant requirement is shelter from rain, due largely to the Barn Owl’s lightly oiled plumage, which makes them more prone to soaking than other species.
So even when contemplating an indoor box - best when there is little risk of immediate disturbance and a permanent & visible means of access (Barn Owls look for holes, not boxes) - the idea is to create a cavity space that is enclosed on at least three sides and has at least one internal baffle to allow the inhabitants to hide away from view.
An important design element of Barn Owl nestboxes is the provision of a front shelf or tray, which will allow fledglings to exercise their wings before first flight - Barn Owl chicks take a long time to fledge (about 8 weeks on average) and, once fledged, remain dependent on their parents for a further three to five weeks.
The ideal size of the Barn Owl box is large - a minimum of 15” x 13” x 25” is recommended, with 6” ledge and 8” x 6” entrance (36 x 32 x 60cms with 15cms ledge & 19 x 15cms entrance). A removable lid or panel should be included for qualified inspection and occasional clearing out between occupants. A converted tea-chest also makes an ideal indoor nesting box for a Barn Owl.
An indoor box should be securely nailed to beams, ensuring that no nails, screws or other sharp edges or points are left to protrude into the box or any part on which the birds might perch. It should be positioned as high as possible - at least 10 feet (3m) above ground level, but in the case of unventilated modern farm buildings, below the apex of the roof, where it can get very hot in summertime. It is best to have the front opening of the box directly facing the owl’s point of access to the building. Alternatively Barn Owl boxes can be fixed under the eaves of remote buildings and are likely to be as equally as successful if they provide privacy, shelter from the rain, direct access and are spacious enough.
Exterior Barn Owl boxes are best positioned in trees well out of reach of the casually curious, (but not so high that any stray owlet might be killed in the fall to earth) either at the edge of woodland overlooking open land, or in large isolated trees or on purpose-built poles located on open meadow or grassland at a location at least half-a-mile (1km) from the nearest busy road. The box needs to be sited in or close to habitat that has an abundance of suitable prey - small mammals, etc. Visibility from the nest and a clear flight path to it are essential. Equally important, the box needs to face away from the prevailing wind & rain direction, usually towards the south east.
Tree-sited nestboxes are more likely to be used by other species than those in buildings. The box should be firmly and securely fixed to its support. Fixing a box to a tree with nylon cable ties or bolts is certainly the most conservationally correct. If possible, the box should be angled so that the floor slopes slightly away from the entrance, so that eggs remain dry & protected.