September 21st - Building bat boxes, Crawfordsburn.

Leader; Adrian Woodley

After last summer’s very interesting bat talk and walk when we saw and listened to pipistrelles (Pipistrellus pipistrellus) feeding on the wing. We decided to return to Crawfordsburn Country Park to make bat boxes.

Adrian Woodley, who answers to Woody, is a member of the NI Bat Group and an entertaining speaker. He gave a short talk to the six Club members present. There are currently eight species of bats in Northern Ireland. There are several varieties of Pipistrelles in Crawfordsburn Country Park, four different species were identified there during the 2012 Bioblitz, Nathusius's
Pipistrelle (Pipistrellus nathusii), Pipistrellus pipistrellus 45kHz, Pipistrellus pipistrellus 55kHz, Pipistrellus pygmaeus Soprano Pipistrelle. The pipistrelles are Britain's smallest bats, are generally brown in colour, and have fast 'jerky' flight. An individual can eat up to 3000 insects a night. He also gave us details of suitable heights and positions for the boxes in trees and under the eaves of houses.

Under his watchful eye the group started, on packs of pre-cut wood, to construct ten bat boxes. Woody was on hand at each stage along the way to provide the extra muscle needed at times.

The group made bat boxes for themselves and other members or friends.

Two of the bat boxes were given to the National Trust to be put up on trees in the National Trust Reserve at Minnowburn.

We look forward to hearing news from the various sites of the bat boxes in the years to come.

Pamela Thomlinson

Bat roost boxes placed on trees or buildings can attract bats, especially if placed in areas lacking roosts and close to feeding areas. These boxes simulate tree holes and can be used by large numbers of bats of most species. A box with each internal dimension about 10 centimetres can hold 50 bats or more.

Box shape and size are not critical, but front or back depth should not exceed 10 cm because bats like narrow spaces. Very rough sawn timber at least 2.5 cm thick should be used. Wood can be roughened by making many shallow horizontal cuts inside and out. Bats often alight on the outside and crawl about before entering. Entrances should be 15 to 20 mm wide and at least 50 mm long - or the full width of the box.

It is best to have a means of inspection: a lifting lid is easiest to construct. If birds nest in boxes, their nests may be cleared out in autumn, but bats will sometimes roost in boxes with nesting birds.

A specialist booklet on this subject is available from the Fauna & Flora Preservation Society or from DOE.

You can find a Guide to Bat Boxes on the Bat Conservation website as well as how to build your own.

More information can be found on the NI Bat Group website.

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One version of a bat box

Common Pipistrelle (Pipistrellus pipistrellus)

Photo by permission of Austin Hopkirk