Monday 5 October 2015

New houses for people - and for Swifts

A new social housing development by T J Evers, on behalf of Sanctuary Group, of twenty affordable houses in Northumbria Close, at the northern end of the village of Haddenham in Cambridgeshire is now complete. As it is a greenfield site, with much of natural history interest in the surrounding area, the developers agreed to incorporate biodiversity enhancements in their plans.

An environmental impact assessment of the site produced a record of Great Crested Newt. However, in consultation with Haddenham Conservation Society, a provision was written into the recommendations written by the eco-consultants, MLM, and subsequently into the planning approval requesting the installation of nestbox accommodation for bird species known to nest in buildings. In the event, this meant primarily Swifts.

Jake Allsop and Dick Newell of Action for Swifts, visited the site and had constructive talks with the building contractors, T J Evers. We offered them a simple solution: to incorporate nestboxes made from clay airbrick liners inside the brickwork of the buildings, concealed behind slip bricks (a ~1 inch slice of brick) with an entrance cut in it, in most cases on the gable end. This is a low cost solution, and easy for the bricklayers to implement. [We have used clay airbrick liners on other projects here and here]

Example of a finished entrance
In this project, the exterior slip brick with its entrance slot is  mounted on the external face of the nest cavity. In this way, the provision of nesting accommodation is achieved without compromising either the fabric or the appearance of the building. 

Fourteen nestboxes were installed. Even in August and during the ongoing building work, workmen reported seeing birds entering some of the boxes. We know that one was a Great Tit, and the others were House Sparrows, but earlier, there was one report of a Swift seen in the vicinity of a box. We will need to monitor the situation closely next season, and if we can persuade one or two house owners to play attraction calls, there is a good chance of enticing Swifts.

Unfinished nest-box, showing the exposed
airbrick liner before covering with slip bricks

We learned something on this project: The size of the access hole to the nest cavity is critical. The recommended dimensions are Length 65-70mm, Height 30mm, but we know that at 30mm, Starlings can squeeze in, so we recommended a height of 28mm (tolerance 27mm-29mm). (Swifts will get into a hole as low as 25mm, but as they wriggle to get in, they may be vulnerable to predators).

In the event, there was some variation in the size of access holes, which is understandable. It suggests that in future, the boxes and their entrances should be pre-fabricated.

The building contractors were entirely enthusiastic and supportive, and it is to be hoped that they will take the message with them to future housing developments that they work on. We also hope that the message from Northumbria Close Haddenham will be heard by other developers across the land. It's the only way we can be sure that there will be Swifts in our skies in years to come.

The nest box entrance is barely visible in this gable end