Thursday 3 May 2012

Emergency Mitigation Swift Bricks

Contributed by Dick
We were alerted to a situation last week where an asbestos roof was ripped off an old Victorian building in St Neots, a week before 6 pairs of breeding swifts are due to return to their nest-sites under the asbestos. The old Brook Street factory site, recently occupied by the ATS tyre company has held a thriving colony of Swifts for many years.

Air brick liner about to be cut with angle grinder
Some fast foot work by Alison Pearson and, particularly, by Bill Murrells who managed to get approval from the owner-developer to incorporate swift bricks into the top layers of brickwork, partly hidden behind a 220mm barge board. Commercial swift bricks were out of the question, given the short notice. Bill came up with the idea to use terracotta air brick liners to fashion rather nice looking nest-boxes. The deadline for delivery of the Swift bricks to the brick layers is Friday morning 4th May.

Completed nest-box with roofing felt extension
Bill scoured every builder's merchant around Cambridge and succeeded in buying 12 air brick liners at about £6 each. A morning with an angle grinder, roofing felt and glue resulted in 12 completed nest-bricks with internal dimensions 270 x 175 x 100mm high.

The developers were unable to allow more than 1 air brick-liner per nest-box. Ideally we would have liked to have used 1.5 or even 2 liners per nest-box. However, although the length of the liners is 208mm, we have managed to increase the internal length to 270mm by using the space normally occupied by mortar.

We will have more on this story as it unfolds.
10 completed swift bricks

Update 09/05/2012:
As one can see from this post the bricklayers thought that they could not allow the use of roofing felt within the wall. So we ended up with nesting spaces about 210mm x 175mm, which we hope the Swifts will like - it is certainly a nicer space than what they had before. In conversation with the bricklayers, they agreed that, with the benefit of hindsight, longer nest-boxes made of 1.5 air brick liners would have been acceptable.

Computer model of swift brick in situ, behind barge board


  1. Hallo Dick and team.

    I like the cost effectiveness of this approach. What stops nesting birds from encountering other nesting pairs (if that's at all a problem), what forms the side wall? Why is the terracotta box lined with roof felt if it's not being exposed to rain, doesn't that make the box sweaty for the birds. I'd have thought roof felt on the base to give the birds grip would be the preffered approach.
    I'd have some reservations about using this box at any location where sparrows might be able to fill it up with nesting material so wouldn't be promoting it for sites such as Fulbourn (I always try to use a box type that has the capacity to be cleaned out).
    Please don't take this a criticism, I love hearing about solutions to ecology problems where different disciplins come together.
    Rob M

  2. All good comments Rob, Swifts competing for nest-boxes is a common occurrence, whatever nest site they are after, that's what 'bangers' are all about. As you can see from the next post, the brick layers did not use the roofing felt extensions, which was there to try to extend the length of the boxes; a former for the mortar if you like. We think the ratio of entrance size to box volume should provide adequate ventilation. Although we think they prefer something rough, Swifts will nest on hard smooth surfaces, Once the scaffolding has gone, it is unlikely that the boxes will ever be accessed for maintenance; a common technique is to remove sparrow nests with a bent coat hanger, outside the breeding season. This would be relatively straight forward in this case, as the inside is accessible from the entrance. A number of commercial Swift bricks would have the same issue. Anyway, sparrows need help too! Dick