Duchy of Cornwall Bird Box Survey Returns for 2026 Season

After more than ten years of waiting, swifts have finally moved into nest boxes built into Duchy of Cornwall homes, and residents are being asked to help track what happens next.

The annual Big Duchy Bird Box Survey returns on 10th May, monitoring built-in nest boxes across Duchy developments at Nansledan and Tregunnel Hill in Newquay, Trevethow Riel in Truro, and Poundbury in Dorset. It runs through to August.

A landmark year for swifts

The 2025 survey recorded six swift nests across Tregunnel Hill and Poundbury, the first time the species has been confirmed using boxes built into Duchy homes. The Duchy has worked with the RSPB for over a decade fitting so-called swift bricks into new builds. These look like ordinary bricks or blocks from the outside but are hollow inside, giving cavity-nesting birds somewhere to raise their young.

Dr Thaís Martins, the biodiversity expert who leads the survey, said the result was worth the wait. “Seeing swifts begin to nest in the Duchy’s boxes for the first time is incredibly exciting. These birds are famously slow to adopt new nesting sites, so this was always something we expected would take time.”

She added: “What this shows is that by putting the right infrastructure in place and being patient, we can create real opportunities for species that are in long-term decline. We’re hopeful this is just the beginning and that we will see many more swifts using these boxes in the years ahead.”

📷House Martins using the built-in nesting boxes at Tregurra Park. Photographed for The Duchy of Cornwall by Hugh Hastings

The numbers behind the survey

The latest results show 1,497 nest boxes installed across Duchy developments, up by almost 200 on the year before. Of those, 684 (close to 46%) showed signs of use during the 2025 breeding season.

House sparrows were the most common species recorded with 159 confirmed nests, followed by house martins on 93 and starlings on 71.

The project, which marked its 10th anniversary last year, aims to install an average of one nest box per new home built and forms part of the Duchy’s wider work on habitat creation and green spaces.

Pressure mounting for mandatory swift bricks

The findings come as pressure builds on Westminster to make swift bricks compulsory in new developments. The UK Government recently consulted on the idea, and the Scottish Parliament passed a law requiring them in January.

Conservationist, author and campaigner Hannah Bourne-Taylor, who is leading the campaign for mandatory swift bricks in building regulations, has thrown her weight behind the Duchy project.

Hannah said: “Swift bricks are paramount to the prevention of swifts becoming extinct in Britain. The housing sector must take responsibility for the only category of birds reliant on buildings to survive and follow the Duchy’s leadership when it comes to swift brick installation to secure the only permanent nesting habitat for these iconic birds.”

She continued: “The Big Duchy Bird Box Survey is such an important survey because it shows that swift bricks really do work: if you build it they will come. The more people take part in the survey, the better because the more evidence collected, the stronger the case for installation which is urgently necessary if we are to save these birds.”

📷Starling - Hugh Hastings

How residents can take part

Dr David Cope, Executive Director for Purpose at the Duchy of Cornwall, said the project was about more than just birds. “The nest box initiative is an example of how we are embedding nature into the fabric of our communities from the outset. It not only supports wildlife but helps residents connect more closely with the natural environment around them. We’re keen to recruit even more spotters for this year’s survey and look forward to seeing the results.”

The survey goes live on 10th May, with residents asked to record activity in their nest boxes via a dedicated Facebook page.

Residents in Nansledan can also hear more from Thaís at a talk on 12th May at 6pm at the Nansledan Community Centre.

She added: “The survey is a fantastic way for residents and families to get involved in a real citizen science project. Every observation helps us build a clearer picture of how these species are responding and how we can continue to support them, so we hope as many people as possible take part this year.”

📷Sparrows using the built-in nesting boxes at Nansledan. Photographed for The Duchy of Cornwall by Hugh Hastings