Sunday, 13 June 2021

Cottenham Village Hall

Triangular colony boxes in the apex of a gable have become quite popular. We were presented with an opportunity in a gable which had projecting beams, which could have limited the size of the triangle. However, the shape contained by the beams lead us to a new and attractive shape. which might look good in any gable.

This idea is appropriate. for shallower roof slopes, in this case, 30°.  Normally, a triangle has 1, 2 then 3 ..  chambers on each level. With a shallow roof, it may be better with 2, 4 then  6 ....

However, in this case, we chopped off the corners of the triangle and went for 2, 3, 3 giving 8 nest chambers.

The resulting colony box would make an attractive feature in any gable with a shallow sloping roof, and easy for architects to include as a module in their designs

Computer model

Internal structure

Installation complete with tweeter

Village Hall Pavilion with swift boxes


Sunday, 28 March 2021

PVC nest boxes

Some years ago, I visited a friend,  Maurice Wilkinson, who had an array of nestboxes for Swifts and House Martins on his house, with a high occupancy rate. Some of the Swift boxes were made of PVC, the same material that is used for soffits. This inspired the idea for the Model 30, with its PVC roof resulting in John Stimpson upping his production to over 26,000 nestboxes by March 2021

Maurice's PVC swift boxes have now had swifts in them for 5 years, and there is no sign of degradation. One might have expected some damage caused by Swift claws on the entrance hole, but they remain unscathed.

Here is a short video of nestling Swifts in one of Maurice's PVC boxes:


PVC as a material is nice to work with, it screws together to make a robust construction, it has good thermal properties, it is lighter than wood, it will never rot, so what not to like? With a suitable primer, it can be painted. It is more expensive than plywood, but not prohibitively so.

We have recently looked at making nest boxes out of 9mm PVC for the complete structure. As a result, we have built 3 prototypes: A Model 30, a Model 31 and a nest box suitable for embedding in external wall insulation (EWI). 

Our conclusion is that PVC is a promising material.

PVC Model 30

As the Model 30 is intended for exposed situations, built in PVC, it will be even more resilient, especially from water that may run down the back. This prototype was made by Simon Evans. The body is painted with Sandtex 'Mid Stone'.

PVC Model 30 painted with Sandtex 'Mid Stone'


PVC Model 31

The Model 31 is designed to go under broad horizontal eaves. It is intended for well-sheltered locations, so the main advantage of PVC here is its light weight. Here we made a double box:

Computer model

PVC Model 31. The small corner pieces attached to the front enable precise relocation of the front after installation

PVC EWI box

We were asked for a solution to embed in External Wall Insulation. When EWI is applied, it is between 90mm and 110mm thick with an additional thickness of render on top, but there is not enough depth for a Swift box. There are 2 choices, either penetrate the wall or have the box projecting outside the insulation. We described the former approach here, using a rendered S Brick. As embedding plywood in EWI is probably not a good idea, we developed a solution that does not penetrate the wall, made of PVC:

Section drawing

Appearance after installation

 
The PVC used here is coated in 'Anthracite Grey'


Monday, 25 January 2021

Duchy Big Bird Box survey 2020

There seems to be a gathering momentum for provisioning nest places for cavity-nesting birds in new development, particularly in the south west, where the Duchy has an ambitious policy of providing an average of one nest place per dwelling. What is often lacking is adequate monitoring of these projects, but this report by Dr Thais Martins is very welcome, providing valuable data to support what we advocate.

Although it is early days, the results reported so far are most encouraging with significant numbers of House Sparrows, Starlings, House Martins and the first prospecting Swifts. This is a good example of community engagement in a citizen science project. See The Big Duchy Bird Box Survey

Photo: Hugh Hastings and the Duchy of Cornwall
Swifts often take longer to find new nesting places, but it bodes well for a future with vibrant Swift colonies in all the developments surveyed.

There is much detail in the paper highlighting occupancy rates by different species in different box types  and on different aspects.

As the data builds up over the years, this should provide some guidance as to what works best.

There is now a common understanding that a Swift brick can be considered as a 'Universal' bird box, and that sparrow terraces are not cost effective. The numbers of birds found occupying Swift bricks in Duchy developments confirm the universal nature of Swift bricks.

In this study, of 515  swift bricks, 192 were used by House Sparrows, Starlings and House Martins, but of 12 sparrow nest chambers in 4 sparrow terraces, only 2 were used. Although not significant at the 5% level it does point towards House Sparrows preferring Swift bricks

Download the  PDF