Animal homes | Bird boxes

Introduction

Designed and sited nestboxes can be extremely valuable in allowing many species to nest and rear young. Bird boxes are sometimes more favourable than natural sites, due to the strength, durability and protection from predators which boxes offer. As old or rotting trees are felled or blown over in gales, there are fewer holes for birds to use, boxes help.

Method

Wooden boxes should be around 2.5cm thick, allowing sufficient insulation from extreme temperatures. Also allowing for ventilation and drainage.
The picture below shows the cutting pattern from a metre of wood. This design is suitable for small birds such as tits or nuthatches. The hole on the front of the box should be about 3cm wide, the diameter can determine what species you may get nesting in the box. Other species, such as nuthatches may make the hole smaller by using mud. For an open fronted box cut the front panel in half, good for robins and sparrows.
Nail together with panel pins, and cover the hinge with rubber or carpet to prevent rain leaking inside the box.

Wooden nest box for small birds, cutting pattern

Wooden nest box for small birds, cutting pattern

Siting nest boxes

Nest boxes should be sited away from direct mid-day sun, and from westerly winds. A south-east orientation is usually best. Shelter from rain is important, so keep boxes away from the wet side of a tree trunk where the rain water flows down in a torrent (look for the presence of algae indicating the run off points). To give additional shelter to the entrance of small boxes, angle them forwards slightly.
Open nest boxes should be mounted tilted upwards so the nest rests in the back of the box. Prickly or thorny bushes make good sites, especially good protection from ground predators. Chicken wire is a good idea to make a cage around the entrance of the box.
The hole entrance must be clear enough from the trunk and branches to allow a convenient flight path in.
The density of the boxes depends on the species and habitat involved. A good plan is to begin with a few boxes more or less uniformly spaced, and keep adding until it is clear that lack of nest sites is no longer limiting the population. About ten assorted boxes to a hectare is a typical density.
Place nestboxes at different heights, on a variety of trees so there is a selection of sites for birds. Free hanging boxes from branches are favoured by some birds, whereas other birds like 2-3 metres above the ground.
Aluminium nails can be used to fix birdboxes to trees, these will not rust or damage tree. Twine or straps can also be used, but must be checked to make sure the the tree is not being strangled.

Large bird boxes

Larger birds that can be encouraged into the garden or green space are the kestrel, owls, swifts, house martins, and doves. The box should be open fronted, to the dimensions shown below.

Kestrels which are common in urban areas like to nest up high, so the box should be sited over 7m from ground. Again south-east facing with a good flight path. Grey squirrels may take over this type of box. Prevent access by choosing isolated trees or poles, with a collar around the trunk or pole.The box can be attached directly to the side, or in a large fork of a tree.

Diagram of a Kestrel box, Suitable for Owls, kestrels, doves, house martins and swifts

Diagram of kestrel box

dimensions (in cms):

2 side panels: 53 x 30 x 2
1 roof panel: 70 x 36 x 1
1 floor panel: 57 x 36 x 1
1 rear panel: 30 x 36 x 2
1 front panel: 12 x 36 x 2

 

tip: Have a perch on one side of the box, you can make this from an old branch.

Barn owls like living in tea chests! With dimensions of 60cm length x 46cm width x 46cm height, with an entrance 23cm square. The box must have a lipped tray at the front to let young owls walk out of the nest. The best place is a quiet undisturbed building away from busy roads, fixed to a beam in a dark corner of the building. Barn owls are specially protected by law, even the box once placed should not be visited without a licence.

Maintenance of bird boxes

All boxes should be cleaned annually, Owl, Swift and tit nests are generally heavily infested with various parasites and must be cleaned by the autumn. Check all boxes are draining properly, lay down some woodchips inside, make any necessary repairs in late winter or early spring before the breeding season.

Baby Birds

If you find young birds in your garden that seemed abandoned - leave them alone! In most cases the parent birds are not too far away, probably searching for food, and they will return once you have gone. Only intervene if you are sure the young bird has been orphaned - raising a baby bird is a huge commitment.

Ivy

Ivy has been persecuted, like some birds! However, it is a valuable addition to your wildlife garden. Dunnocks, chaffinches and blackbirds can nest safely hidden among the twining stems. The evergreen leaves provide shelter from the rain and cold, and insect food for small mammals and birds. The berries are a valuable source of food in winter when other supplies are running out. Butterflies also use ivy to overwinter in.
Ivy has been thought to strangle trees, this is not so - it is not parasitic. The wildlife value of its presence as a benefit to wildlife is obviously greater than it being absent in the garden.

related links

British Trust for Ornithology For more bird information, why not do a bird survey?