The use of nestboxes by Little Owls seems to vary from country to country and county to county. In Wiltshire and in Lincolnshire nestboxes appear to be readily occupied by the birds but in Cheshire they have been slower to use artificial sites. In Saarland and Bavaria in Germany the population has seen an increase attributed to nestbox schemes. It may simply be that in some areas there are sufficient natural sites for the birds and in others a shortage of sites inhibits the population so the provision of owl boxes creates an opportunity for expansion.
A wide variety of nestbox designs have been used by Little Owls. The essential design requirements are; a very small entrance hole (70mm), a narrow tunnel or baffle arrangement, and a dark nesting chamber. The nest box design featured here has been particularly successful in Lincolnshire with boxes installed in open-sided farm buildings (both traditional and modern types) and “crew yards”. The Barn Owl Trust is grateful to Bob Sheppard for providing the details. Bob’s design is simple to build, the access door makes cleaning out very easy, and the depth of the box helps to prevent the young from falling out of the box prematurely.
The box is made of 12mm tanalised softwood ply and held together with 40mm rust-proof screws. Please avoid using hardwood ply unless it is stamped ‘FSC Approved’. Consider the proposed location of the box when deciding on the position of the access hole and internal baffles. Wherever possible the box should be positioned in such a way as to allow the owls to walk out onto a branch or wall top. Construct the sides first and then cut the floor to fit within the sides as this helps to keep the interior dry. The removable panel that allows access to the main chamber should always be incorporated. Use brass hinges to prevent rusting and remember when you fit the panel, that wood swells when damp.
If located outdoors, use thick roofing felt on top of the box, drill a 10mm (½”) drainage hole in each corner of the floor, treat with creosote substitute and allow to dry thoroughly for 2 or 3 days before erection. All joints should be sealed with good quality sealant such as ‘Ever Build – Weather Mate’.
If located in a very sheltered position (ideally in a building), a small ‘exercise platform’ can be added immediately below the entrance hole and above the inspection hatch. However, in an exposed position the addition of a platform could cause rain to splash into the entrance hole (this could wet the nest contents and should be avoided). Providing a perch just in front of the box could be beneficial. Or buy a Little Owl box with Hanging kit included that’s built to last.
The owl box should be erected horizontally, a minimum of 3 metres (10′) above the ground on a wall top, beam or tree branch so that owlets can walk in and out prior to fledging. Little Owls seem to prefer nestboxes placed in open-sided or open fronted buildings rather than enclosed types.
A ‘Nestbox Hanging Kit’ is included with all Barn Owl Trust Little Owl nestboxes or can be purchased separately if you have made your own box.
For monitoring the occupation of boxes it is useful to paint a ring of Tippex around the entrance hole and watch for its discolouration.
A thin layer of untreated wood shavings or bark can be provided as a floor covering.
You are responsible for your own safety – please assess the risks and be careful.
Clearing out nestboxes
After 2 or 3 years of occupation the box should be cleared out during autumn or winter.
As with Barn Owls, Little Owl nestboxes should be cleared out periodically to reduce the risk of young owls getting out prematurely. Any depth of debris more than about 1” (25mm) should be removed. Little Owl nestboxes are usually small enough to deter use by species such as Stock Dove and Jackdaw, but any evidence of these species (sticks, bits of straw, etc.) should also be removed.
If outside, check that the box is still well-fixed, in good condition and dry inside. If there is any doubt that the box will still be up by the next time you check, strengthen its attachment or take it down and re-hang it. In the case of tree-mounted nestboxes, be aware that trees expand as they grow and nestboxes can literally be pushed off as the exposed parts of screws and nails gradually disappear into the tree. Similarly, anything wrapped around a trunk or branch may need to be slackened off.
Pairs may become territorial from late winter onwards so any works are best carried out in late autumn once young have fledged and dispersed.