The Hawk and Owl Trust set out to test the idea that a shortage of nest sites was at the heart of the decline in the kestrel population across the UK. Over three years volunteers erected kestrel nestboxes along the line of major traffic routes, but sited a safe distance from the actual traffic. Read more about the Kestrel Highways project here.
"It is not our intention to place kestrel boxes adjacent to or alongside major roads. This would be lethal for the emerging young kestrels that would soon become traffic casualties," explains the Kestrel Highways coordinator, Maj Nigel Lewis MBE.
This page details the sort of nestbox, how to build one and how to install one safely and for greatest conservation effect. The information is an edited extract from Boxes, Baskets and Platforms: Artificial nest sites for owls and other birds of prey published by The Hawk and Owl Trust price £5. This, and a selection of ready-made nestboxes, are for sale from the Trust's online shop: Boxes, Baskets and Platforms or Ready-made nestboxes
Download this guide and diagram here.
Installing a kestrel nestbox
Choosing a site
Nestboxes for kestrels only need to be sited between 3 to 5m (10–16 feet) from the ground if on private land, higher if vulnerable to public access.
Nestboxes should not be close to major roads, as emerging young would soon become traffic casualties. Boxes should face onto open land and not be hidden by foliage or thick ivy; the more obvious they are the better. If sites are likely to become obscured by the growth of ivy or tall scrub, this should be removed when the box is installed.
When installing boxes during the winter it is important to remember that they may be less obvious to the birds when the tree is fully in leaf. The box entrance should face away from prevailing winds and direct rain. It should be tilted so that rain runs off the front. The box is designed to include a perch but should be placed where there is plenty of perching in front of the box to enable the young kestrels to branch properly
Artificial nest sites should be in place before the end of November to give the best chance of success the following year. It can take three years before a site is used for nesting, although there are often encouraging signs of roosting, such as a build-up of pellets or feathers, before then.
Installing the box
The Trust pioneered non-metallic fixings such as plastic cable ties and
nylon bolts, and uses them routinely when installing boxes in living trees.
These materials minimise damage to timber and , if felling takes place, they present no hazard to chainsaw operators and those carrying out mechanised harvesting. For this reason, the wooden mounting boards used to secure tree boxes are primarily designed for these specialised forms of attachment but also allow for more traditional methods, using nails or corrosion-resistant Timberlok screws with washers that can be adjusted or removed if required, if these are the only option. The mounting board is screwed or bolted to the box at installation.
To install nestboxes with nylon bolts it is best to select an upright tree trunk with a flat face, free of knobbles and projections. The tree is drilled with a 14mm wood-boring auger bit to a depth of about 38mm (11/2 in). A 15mm diameter 100mm-long nylon hexagon-head bolt is screwed into the hole with a wrench and socket. The box is then hung on the bolt through the pre- cut keyhole at the top of the mounting board. The head of the bolt is then cut off with a hacksaw. A further hole is drilled into the tree through the bottom hole in the mounting board, and a second bolt inserted, tightened and the head removed. Two nylon washer-faced nuts are then tightened on to the stubs of the protruding bolts. They can be slackened each year as the tree grows. If boxes are fixed too rigidly they distort quickly and eventually break , particularly on fast-growing trees such as poplar, willow and sycamore, which should be avoided.
A 50mm (2 in) layer of nesting material must be placed in the box for the kestrel eggs. Shredded bark mixed with finely shredded paper can be used. Once used, the kestrels’ own debris, pellets etc form the basis of future nests.
If birds have made no attempt to use a box after three to four years it may be useful to consider moving it to another location.
Position nestboxes at a sensible height to minimise injury if the ladder falls — 3 to 5m (10 to 16 feet). Wear a hard hat when climbing. Most of the smaller birds of prey will not attack you at the nest.
Monitoring
Inspection is essential in any conservation or research scheme. Boxes should be individually numbered and locations and contents accurately recorded every year.
Remember to ask for permission from landowners to install or inspect artificial nest sites, and inform them of your successes. Boxes need only to be checked once a year and this is best done when the young are small.
Most kestrels are tolerant to disturbance at this time, but can be less so when egg-laying and incubating. As a rough guide, they should be inspected in early to mid-June. However, timing can depend on many factors such as spring weather and annual fluctuations in the food supply.
Maintenance
Sites should be checked each winter and any unwanted material cleared. If the box has been used by a bird of prey, pellets and lining materials should be left and only removed when they have built up above 100mm
(4 in) or so.
Edited extract from Boxes, Baskets and Platforms: Artificial nest sites for owls and other birds of prey published by The Hawk and Owl Trust price £5.
