Tuesday 19 February 2019

Guidance for including bird boxes in residential development

We have recently started walking around new housing developments in South Cambridgeshire to see what is being done in the way of Biodiversity Net Gain. In particular we have been looking to see what Swift bricks have been installed.

by John Willis & Dick Newell

Our starting point was the planning portal on the council website from which we derived maps showing exactly where every Swift brick and sparrow terrace was to be installed. Councils should carry out this kind of audit themselves, but they have no resources to do it. Thus the volunteer sector (SLN members) could have an important role to play.

As we do not wish to embarrass anyone, we will not say where we went, but we have the following observations:

1. The number of Swift bricks conditioned by the planners is low, between 10% and 20% of dwellings. There was a high percentage of empty gables. It is becoming generally accepted that It should be nearer 1 per dwelling on average, see page 101 of RIBA Publishing's Building for Biodiversity 2nd edition 2016.
2. About equal numbers of sparrow terraces and swift bricks are conditioned. Integral sparrow terraces contain three nest chambers but are seldom if ever used by more than one pair, swift boxes a metre+ apart will be used by swifts and sparrows.. There would be better outcomes for both sparrows and Swifts if there were more Swift boxes and fewer sparrow terraces.
3. Many of the conditioned Swift bricks were not installed, and, at the time of writing, we do not know what will be done to correct these omissions. None of the specified nest boxes are suitable for retrofitting.
4. Many Swift bricks were not placed high up in the gable, but in sub-optimal places at a lower elevation. Some swift bricks were even specified in garage gables, barely 4 metres high.
5. There was never more than 1 swift brick in any one gable. As Swifts and House Sparrows like to nest in groups, why not 2 or more in suitable gables?
6. Some swift bricks were placed in facing gables about 8 metres apart - this is not the clear flyway that is the ideal.
7. Some of the European sourced swift bricks are not compatible with UK brick sizes, requiring the bricklayer to cut up to 8 bricks to get them in.

Our conclusion from these observations is that there is work to be done to get both planners and ecologists up to speed in specifying bird boxes in residential development.
We have drafted some guidelines that you can read here

Figure 1: Recommended positions of internal nest boxes for Swifts and House Sparrows.
Other possibilities include holes in soffits and fascias.

No comments:

Post a Comment