|All Saints, Landbeach|
In the two churches we played attraction calls using the Cheng Sheng player-amplifier. In St Neots, no calls were played, but the boxes were installed as mitigation for lost nest sites.
In all three cases, the entrances are set back from the 'outside world': behind louvres in the churches and behind a thick barge board in St Neots. All occupations were achieved within a year or 2 of installation.
Further evidence of the acceptability of small boxes is at St Mary's Ely: the success rate of the smallest boxes with floor area 100mm x 300mm marginally exceeds the larger boxes. Also the successful Losser box in Holland has a floor area of only 160mm x 165mm. The Ibstock swift brick, with an internal width of 100mm is accepted by Swifts.
So, it is established that boxes with a small floor area are accepted by Swifts. Could they even be preferred? We are now trying to establish where the limits are with headroom, before occupancy rates drop off to an unacceptable level. There are many examples of Swifts nesting successfully with low headroom under tiles, and we know of one occupied box in Cambridge with internal headroom 75mm, floor area ~120mm x 375mm. These birds raised 2 chicks.
We are now in the process of reengineering the Landbeach church cabinets. The louvres are close together (80-90mm), so, originally, to give what we thought was adequate headroom, the entrances were behind every other louvre gap. The original four cabinets had 4 boxes each with floor area 200mm x ~400mm and internal height ~180mm.
If small boxes are at least as effective as large boxes, then they should be preferred - they are less obtrusive and easier to install.