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Cavity nesting birds: their decline, and the campaign to help safeguard them from national extinction

Author Hannah Bourne-Taylor outlines the campaign to make swift bricks compulsory in new housing across Britain to help safeguard cavity species from becoming nationally extinct

February 2023

Four species of cavity nesting birds (Common swift, House martin, Common starling, House sparrow) are on the red list of highest conservation concern, a term defined by the need for ‘urgent action’. Together with leading scientists and sustainable building assessors I created a national conservation campaign with a petition at its core, asking the Government to make swift bricks compulsory in new housing across Britain to help safeguard these species from becoming nationally extinct. Make swift bricks compulsory in new housing to help red-listed birds - Petitions (

Loss of nest sites

Since 2002 when House sparrows and Common starlings were added to the red list, scientists have raised loss of nest sites as a possible factor for their decline (BTO Research report No 290 2002) with awareness that modern buildings contain fewer nest sites for birds, and that those in old buildings may be being destroyed (Moss 2001).

This year’s government ECO+ scheme extends the initial scheme that has already made 2.4 million homes more energy efficient by insulation measures including roof and wall insulation such as soffits. This will further negatively impact cavity nesting birds.

Loss of nest sites of swifts are a particular concern because swifts are site loyal, adults returning to the exact nesting site year on year for their 20-year lifetimes. With one of the shortest breeding seasons of any bird, the individual pairs returning to find their nests blocked off, risk being unable to find a new cavity to nest and breed in, thus contributing to the population decline of over 50% in the past 20 years (BTO). Many individuals fatally break their wings trying to get back into their nesting sites, after 9 months on the wing.

Current policy

In the Netherlands, nest sites of swifts are legally protected year round. Loss of nest sites by renovation are compensated for with the installation of either nest boxes or Swift bricks.

In the UK, no such protection exists. However, the Government recommends Local Planning Authorities make Swift bricks compulsory in new housing developments.

Swifts bricks, also known as ‘Universal bricks’ due to providing nest sites for a diversity of species, are house bricks with a special cavity that sit flush to the wall. S Brick ( They are recommended in the Design Codes Guidance for local authorities, ready for the implementation of the Levelling-up and Regeneration Bill. There is national best-practice guidance on the usage of swift bricks in the form of BS 42021:2022, in addition to CIEEM. BS 42021:2022 recommends one nest brick per dwelling on average for new-build housing developments. The value of Swift bricks to wildlife is highlighted by National Planning Policy Guidance (Natural Environment 2019 paragraph 023).

Swift bricks have been installed across the Duchy of Cornwall estate, monitored by the RSPB. Surveys are positive. Duchy of Cornwall’s bird box survey results revealed - Nansledan

Many LPAs mention Swift bricks in their guidelines for Local Plans but only some including Brighton&Hove, Cambridge, Edinburgh, Hackney, Sutton, Basildon and South Hadden, have made swift bricks a compulsory condition for new housing. With the new Biodiversity Net Gains, developers are unlikely to include swift bricks since they are not part of BNG so there is no incentive for this crucial biodiversity measure for cavity nesting birds. Despite clear recommendations, the installation of Swift bricks is not common practice.


I am also perusing the need to follow the Netherlands’ policy to ensure there is mitigation for loss of nest sites and raise awareness of the destruction of cavity nest sites as a direct result of the ECO+ scheme.

Extensive case studies collected by the Swift Local Network, comprised of local swift conservation groups, record nesting sites and swift numbers. This collection gives localised examples of nest sites being destroyed, breeding pairs of swifts being displaced, but also Swift brick installation being a success, often increasing the original local population size. On a larger scale, Wakefield & District Housing has collaborated with the local swift group while undergoing the installation of soffits, by making 440 holes and nest cups that have been placed in the space above each soffit. In contrast, the wall insulation (EWI) programme in Dundee targeting 740 properties – and inadvertently the destruction of a colony of swift’s nesting sites, has no such plan despite requests from local swift conservation groups to mitigate the loss of nesting sites.


A nationwide policy for either Swift bricks in new developments and/or mitigation of destroyed nesting sites linked to the ECO+ scheme would make the effort to help these 4 red listed cavity nesting birds efficient.

The Levelling Up Bill would be the optimal route to achieve the changes in legislation, not the Building Regulations as referenced by the government as this would be much slower for birds with plummeting populations.

Please sign the petition and if you can help this campaign achieve its goals, please get in touch with me on the campaign email:

Time is of the essence and my biggest concern is that these birds are not being considered despite being our closest wild neighbours, almost entirely dependent on having access to our walls to breed in (swifts used to nest in tall trees in forests – some colonies still remain in the primal forests of Europe but we cut the trees down here, and remarkably these birds, from one of the most ancient orders of birds dating back 70 million years, adapted to our walls.)

Hannah Bourne-Taylor is an author and photographer. Her nature memoir Fledgling is out now

Follow: @WriterHannahBT

The opinions expressed in this blog are the authors' and not necessarily those of the Link membership.