Monday 8 September 2014

Experiences with small Swift boxes

Since 2006, in my local church belfry in Landbeach, we have had 4 cabinets, each containing 4 large boxes, and the swifts have ignored them, though 3 swarms of bees have not. As soon as we added small boxes in 2013, behind the top louvres, we had success.

[UPDATE JULY 2017: We think we have 6 occupied boxes this year, 3 raised chicks]
[UPDATE JUNE 2018: On 8th June we found 8 boxes with eggs or adults and 1 well-feathered nest]

by Dick

All Saints, Landbeach
We have been getting a gratifyingly high success rate with small Swift boxes. e.g. not only 4 out of 8 small boxes in Landbeach church, but also 7 out of 12 air brick liners occupied in St Neots, and 6 out of 18 small boxes in Worlington church. These boxes have a floor area of 175mm-200mm x 200mm and at least 100mm internal headroom. 

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 NeotsAll 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.

Two of these cabinets will have each box further divided into 4 smaller boxes - each one half the height and half the floor area. There will be 2 entrances within each louvre gap (see cabinet on the right below). In the other two cabinets, each original box is divided into 2 with half the floor area, but staggered in such a way that there is at least 1 entrance in each louvre gap. So, to make this work, there are some boxes at the top and bottom of these 2 cabinets with smaller headroom (see cabinet on the left below)

Part of the incentive for doing this is to make the boxes less attractive to bees, a problem peculiar to this belfry. Bees should not survive a winter in a box this small. But the main incentive is in the nature of an experiment (somebody has to try it), which ultimately may mean modifying one of these 2 configurations to the other in the future, depending on the results.

If small boxes are at least as effective as large boxes, then they should be preferred - they are less obtrusive and easier to install.

Front arrangement of entrances

Hinged inspection doors

(Dead) Swift on concave in box with headroom ~130mm

Swift in box with low headroom of ~85mm

No comments:

Post a Comment