In rccent winters, a large number of dead tawny owls have been found firmly jammed into stove piping in summer cottages in Sweden. The shortage of accommodation has forced them to seek shelter in such places, where they have suffered a painful death. Other owls are equally desperate for somewhere to live.
Setting up nest boxes will help owls. The occasions when you are most likely to hear an owl hooting will be on starlit evenings or nights in February March. If you go out with a map you can mark out the places where you hear any hooting, then you can ask the landowner for permission to set up nest boxes near these areas. Be willing to point out the actual tree on which you intend to place the nest box, in order to prevent any misunderstanding. Use aluminium or copper nails which will present no hazards in any future felling and sawing operations. Normal nails creatcrisks of splinters and injury to operators and damage to machinery should the tree require felling at some time in the future.
The best nest boxes are those made from solid blocks, but you may also make a larger nest box from wooden boxes . Four to five holes should be drilled in the bottom of the box in a straight line. From the inside of the box hammer some large 8 to 10 cm long nails through these holes and into a board which is longer than the box. A hole should be drilled into each end of this board so that it can be nailed easily onto the tree, or alternatively a large hole can be drilled into the board whereby the nest box can be hung up on a sawn-off branch. In the Swedish Hunting Association's game management school at Ostermalma. an excellent device for hanging up heavy nest boxes has been invented which is well worth a mention. The box is hung from a sawn off branch by, for example, a pair of slabs of timber cut from the outside of spr uce logs or some equally durable timber (these offcuts arc available from sawmills very cheaply) being nailed onto the back of the nest box and connected with a cross piecc. A front side, made from boards or wood fibre tiles, is then nailed onto the box, and a square entrance hole is sawn or a round hole is then drilled into it. It is important to use rough sawn and not planed timber for this or else to provide some form of 'step ladder' lilted to the inside of the nest box, below the entrance hole. Young owls leave the nest box before they arc completely ready to fly, while wild duck and goosander young do so only two days after hatching. Without a rough surface to grip with their claws these young find it difficult to get out. A year or so ago, tragedy occurred in a large number of goldencye nest boxes newly crccted in Bergslagen. Some of these boxes were loo deep (for goldencye the entrance should be no more than 25 30cm above the base of the box) and some had no steps, so that when the nest boxes were cleaned in the autumn, they were found to be full of dead young which had been unable to get out.
Sawdust, wood-wool, wood shavings, or last year's grass should always be placed in the bottom of the box, since neither owls, wild ducks, nor goosanders build their own nests. Crushed decayed straw stubble is the best material for goldencye nest boxes; this is very much like the material found in birds' natural nests and so is more likely to stimulate the breeding instinct. Wild ducks and mergansers will line the nest cups using down plucked from their own bodies.
The area below the entrance hole should be strengthened with a board bceausc ducks and mergansers will fly into the hole at full speed and use this part of the structure for braking, thus imposing a lot of strain on it.
The nest box must also be held in place very firmly. The roof should be of hardwood covered with roofing felt and should project slightly over the front to prevent rain coming through the entrance hole (box measurements for the various spccies arc on pages 208 9).
If a nest box is set up near a water course, or better still on a promontory where the icc will break up early in spring, there is a good chance that wild ducks will come to breed in it. In Northern Europe these may include goldeneye, goosanders, red-breasted mergansers and mallard. In Britain you may only be lucky enough to attract goldeneye in the north of Scotland, but goosanders may occupy riverside nest boxes as far south as the River Tyne. Further south, in areas where thev have becomc naturalised, another tree nesting duck the mandarin may use boxes of this type.
The female duck or merganser will sit below the nest box and eagerly call to her young, which throw themselves fearlessly out of the nest, trying to break the fall with their tiny wing stumps. The ground below the nest box should therefore be even and free from sharp stones.
Those who do not have the time, inclination, or ability to make a nest box can buy one in a shop. They can be found in department stores, garden centres and seed merchants. But one should be careful because there are many poor quality nest boxes on the market, and one should check up on all the relevant materials and measurements before buying one.
Below you will find several nest box types which 1 have field tested over some years and can recommend. But there are many many different kinds and if some do not appear here it does not necessarily mean that they are unsuitable. However, it should be kept in mind that wood and wood-cement board arc the best materials, and that one of a nest box's most important characteristics is its insulating ability, since although birds may be breeding for only one month in the year, some species such as tits and wrens may spend six months sheltering overnight in such boxes in the autumn and winter. People who talk about nest boxes and recommend different products often pay far too little attention to this point.
It is also an untrue generalization to say that plastic nest boxes arc unsuitable, but they are susceptible to problems which do not occiy; with wooden boxes. In direct sunlight they quickly heat up inside and great carc should be taken to position plastic boxes so that they are always in the shade.
The box should be designed to allow for easy cleaning after the breeding season and this is often a feature which is forgotten by the manufacturers of plastic boxes. Failure to clean boxes after nesting can lead to a build up of harmful parasites, which may affect the next brood to be reared in the box. Finally plastic may become brittle in sunlight and holding a nest box in the wrong way (eg by an edge) may result in it cracking; the area under the entrance hole is particularly susceptible.
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