Nest Boxes for Small Garden Birds
A Wildlife Tip Sheet from Jacobi Jayne & Company
by ornithologist Chris Mead
All gardens can offer nest boxes for small birds. Even the tiniest gardens should have a box or two and the larger your garden the more you can provide and the greater the variety of birds you will house.
There are two main types of boxes to consider. The first and most straightforward is the tit box which has a hole into an enclosed box. The second and more problematic is the open-fronted box for Robins, Spotted Flycatchers and the like. The problems they pose are very different. Any sort of cavity with a hole of the right size is likely to be occupied by sparrows or tits - whether it is good for the birds or not - whereas even the best possible open-fronted box may be ignored for years by all possible occupants!
Make or Buy?Millions of broods of birds have been reared in Britain in home-made nest boxes knocked together from spare wood. Designs are legion and many are published each year for National Nest Box Week in February. For tits, the thickness of the wood and the size of the base of the box are important. Contact National Nest Box Week for more information (see below).
However, before making your own boxes, it is wise to first consider the considerable advantages of Schwegler 'woodcrete' boxes. The birds are more likely to choose them and more likely to nest successfully in them.
A key advantage of 'woodcrete' boxes is their excellent thermal properties. They keep the birds cool in hot weather and warm in the cold and prevent condensation inside. Materials without these properties - especially plastics, ceramics, thin wood and ply - make poor, even dangerous, nest boxes. Another advantage of 'woodcrete' boxes is that they are rot-proof, predator-proof and extremely long-lasting. Although they can cost up to twice as much as ready-made wooden boxes, they can potentially last ten times as long.
Choosing the right Schwegler BoxesThere are over 50 designs of Schwegler boxes and each one mirrors an ideal nesting hole in shape and size. Since the range offers so many choices, here are my tips to help you.
General tit box. The best general tit box is the free-hanging 2M which is supplied with a stainless steel loop to fix around tree branches. The birds seek it out and use it successfully. It is possible that they realise ground predators will have difficulty reaching it since it has no direct connection to the ground. When they were introduced to the Great Tit study at Wytham the productivity increased by 50% over the existing wooden boxes!
Mounting on walls and tree trunks. In the absence of predators like squirrels and Pine Martens, choose the 1B. This comes with an aluminium nail which can be used in tree trunks without causing any harm, even after many years. If predators are present choose the 2GR with the jutting front and three holes to let in extra light and encourage the birds to nest at the back of the box - it really works, even on a reserve in Scotland where Pine Martens wiped out all the tits nesting in conventional wooden boxes.
What size hole? This is an easy question to answer. Any bird in a nest box is good news so a 32mm hole is the right choice for most boxes, being a perfectly acceptable size for all the tits, Nuthatches and Tree Sparrows. If you specifically want to encourage House Sparrows or are lucky enough to have Redstarts around try the 29 x 55mm oval hole.
Where to put them up? Most birds are not too fussy. Fixing on trees, walls and fences at 5'6" is fine. If you are putting up several boxes you can vary the height upwards if you wish. Free-hanging boxes should be fixed above 6'6" if they might otherwise prove to be a hazard to your head. In an open location it is generally best if the hole faces south-east to avoid the worst of the weather. It should not be in direct sunlight but this is not so important with Schwegler boxes since they are so well insulated. Having adjacent boxes facing in opposite directions may reduce unfriendly interactions between the birds. Never put them close to birdfeeders and birdtables because the feeding birds will be seen as a threat by the nesting birds.
How many? In a medium-sized garden in which natural holes are in short supply, it is worth putting up 4 or 5 boxes. If you find all your boxes are occupied, put up more to ensure there are always spare homes available.
Open-fronted boxes. These are well worth trying but don't expect quick results. Too little is known about exactly what the birds are seeking to always get it right. And of course there are many different aspects to open-fronted boxes whereas the overwhelming attraction for tits is simply the hole! The 2H is a good bet. Fix it on a wall at 6' for Robins and higher for Spotted Flycatchers. Partially conceal it behind a climbing plant if possible. Where predators might be a danger the 2HW is a better choice; it is long and deep so that the birds build their nests at the rear.
Special BoxesThe many other types of Schwegler boxes are worth using depending upon your local circumstances. House Martin nests (9A and 9B) and Swallow nests (10) are a very good idea if the species are around. Fix the former under eaves and use more than one if possible since the birds are colonial; install the latter inside a garage, shed, barn or porch. You will find that these birds are often attracted to the nest boxes but build their own nests nearby.
If you are in woodland I urge you to try the fantastic 'two chimney' Treecreeper box 2B which has worked so well for me. Try the Swift box (17) high up on the wall of your house if you are lucky enough to have these fantastic birds in the area.
Finally the wagtail box (19A) is an excellent idea if you live in a mill or have fast running water in your garden. Such places attract Grey Wagtails like autumn wasps to sticky jam. The same box is used by Pied Wagtails who do not need to be beside water, and the larger version (19) is for Dippers - not a lowland bird!
- To register for annual information on National Nest Box Week send your name and address to NNBW, Freepost 1155, Herne Bay, Kent, CT6 7BR or telephone 0800-072-0130.