The natural nesting site for a Tawny Owl is a deep and dark cavity in a tree, such as the hollow in a broken branch, or sometimes they may use the old nest of a Magpie or a Grey Squirrel.
This nestbox is meant to represent a deep cavity and it should be sited high up on the edge of a stand of trees, and fixed at 45 degrees to the horizontal, either on the trunk or a major branch, and facing east. The support batten should be firmly fixed to the box and nailed into position, using 4 inch or more galvanized nails (fixing method 1 on the diagram); or it may be possible to fit a longer batten across the top of the box and wedge this into a fork between two branches (fixing method 2 on the diagram). It may also be possible to attach the box using wire only (fixing method 3 on the diagram), but ensure that heavy gauge plastic-covered wire is used and is stapled to the nestbox. About a dozen drainage holes (0.25 inch diameter) should be drilled in the base, and a covering of wood shavings put aside.
An ideal size for a Tawny Owl box is 9 x 9 x 31.25 inches internal dimensions, which requires the following pieces of timber of 0.75 inch thickness:
- 2 side pieces 9 x 31.25 inches
- 2 side pieces 10.5 x 32 inches
- 1 floor piece 9 x 10.5
Glue and screw together, using waterproof glue and about 2 inch screws. The fixing batten should be 1 inch thick, and approximately 28 x 4 inches for fixing method 1, or 36 x 4 inches for method 2. Thicker timber can be used, but adjust the measurements to give the same internal dimensions.
This will be a heavy nestbox and will need at least two people to erect it, using ropes and a ladder.
A word of warning! If a Tawny Owl box is occupied, it should NOT be visited in the breeding season! Apart from the obvious risk that disturbance may cause the parents to desert, there is a real danger of injury, as a Tawny Owl will attack any intruder and can inflict very serious injuries, especially to the face.