Encyclopaedia of Birdcare

Nest Boxes

Artificial nest sites for birds and other animals, not always, strictly speaking, boxes as such, as some are in the shape of tubes or cups. As well as the sheer pleasure of watching their occupants, nest boxes have two more serious uses:

• they facilitate scientific study of the breeding behaviour and success of the birds, providing opportunities for observation, recording, filming and ringing

• they increase the availability of nesting places, which may be very significant in areas where there is a dearth of natural nest sites, perhaps because of loss of old trees

In these ways putting up nest boxes can aid both monitoring and conservation of birds and other forms of wildlife.

History

The first nest boxes seem to have consisted of clay flasks and were used in medieval times in the Netherlands to house Starlings and House Sparrows, whose young were then eaten. The first ones provided simply to encourage birds for pleasure or observation were perhaps those put up by Charles Waterton in Yorkshire during the early 19th century, by which time most were constructed of wood. Scientific researchers began to make use of nest boxes early in the 20th century, for example in a study of the House Wren in the USA. As the exact needs of the birds became better known, the modern types of boxes evolved, and materials other than wood began to be used, such as cement, hardboard, plastic and more recently woodcrete, developed by the German firm Schwegler GmbH. Another trend during the last few decades has been the extension in the range of birds catered for, from the original nesters in holes and cavities such as tits and Robins to species like House Martins, kestrels and Tawny Owls, and also to animals other than birds, for example bats, hedgehogs and even insects. Nest boxes are now seen in many gardens and nature reserves, the grounds of schools and other institutions, and increasingly on industrial and commercial premises. Since 1997 the profile of nest boxing has been raised by the annual national nest box week.

Basic types

The most common kinds of nest boxes seen in gardens and similar situations are as follows:

• Hole-type. Normally at least about l5Omm (6in) square at the base, some 2OOmm (8in) high at the back, with a roof sloping down towards the front. A circular hole is made not far from the top at the front or side, its diameter varying according to the species of occupant envisaged, for example 25mm (1in) for Blue Tit and 32mm (l.25in) for Great Tit. Part of the box, usually the top, can be removed for access to the interior. This type is intended for hole-nesting birds such as tits, sparrows and, in a larger version, starlings.

• Open type. Similar to the hole-type, but with the upper half of the front left open, for use by cavity nesters such as Robins, pied Wag-tails and Spotted Flycatchers.

Special types

Among the nest boxes designed for birds with particular requirements, the following are relevant to at least some gardens:

• Kestrels. Boxes for these falcons typically have roughly square fronts open for the top two-thirds, and are about twice as deep as they are wide and high. They are placed in trees or buildings about 5m (l6ft) above the ground.

• Owls. For Barn Owls, a box like that for Kestrels is suitable, but for Tawny Owls a tubular shape is needed, made of plywood on a timber frame and with a square cross-section. It is strapped under a branch at an angle of about 30 degrees, and is intended to imitate a hole caused by a dead branch breaking off.

• House Martins and Swallows. Nest cups for House Martins are secured at the top of an outer wall under the overhang of the eaves, and a double version is available. Use of such artificial nests may encourage martins to build natural ones nearby. Similar devices for Swallows need fixing inside buildings on beams or on walls just below the ceiling, making sure that permanent access from outside is available.

In addition, boxes are now sold for the benefit of animals other than birds, for example the following:

• Bats. These flying mammals have declined greatly in numbers during recent decades, as a result of disappearance of old trees, difficulties of access to roofs of modern buildings, and smaller populations of flying insects. Putting up bat boxes can provide them with sites for breeding and roosting where they might not otherwise exist. Such boxes look rather like those intended for hole-nesting birds, but their entrances are placed lower down and are shaped like broad slots.

• Hedgehogs. Tidy modern gardens have few places where hedgehogs can breed. The best type of artificial site is made in the shape of a dome about 440mm (17.25in) across and about 280mm (11in) high, to be placed on the ground in a dry sheltered spot.

• Insects. The value of insects as food for birds and bats and as pollinators of flowers is now appreciated, and a number of boxes are now available to encourage harmless types. These include a nesting box for bumble bees to be placed on the ground, a hanging block with holes for a variety of insects, and the new insect house made of woodcrete by Schwegler GmbH. The latter contains transparent tubes accessible through holes in its wooden door, so that when the door is opened the lives of its occupants can be observed.

Buying

Nest boxes can be home-made, and most types can be purchased from specialised suppliers of birdcare equipment. Basic boxes may be obtainable from local outlets such as garden centres and pet shops, but these are often badly designed and poorly made. It is best to obtain boxes from firms which stock a good range, including those made of new materials such as woodcrete.

Siting

Nest boxes should be firmly attached to a support such as a tree or wall facing away from the heat of the sun and avoiding the direction of the prevailing wind or rain, i.e., not facing between south and north-west in Britain. They should be fixed at least 1.5m (56in) above the ground, in a position which is as inaccessible as possible to cats and other predators, bearing in mind such routes as the tops of fences and walls as well as parts of trees. It is possible to prevent such animals climbing tree trunks by placing bundles of thorny twigs on the ground below, or by using the wire belt obtainable from Jacobi Jayne & Company for fitting round a trunk.

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