Architects should get behind the campaign to support endangered birds by installing swift bricks in all new UK homes, writes Hannah Bourne-Taylor.

Swifts are small black birds with a sickle-shaped silhouette, the weight of a KitKat. They fly almost 70 miles per hour in level flight, inspiring fighter-jet design.

They spend more time airborne than any other bird on earth, with adults spending nine months of the year on the wing flying to the rainforests in the Congo basin, and young swifts spending three years in maiden flight. Doesn’t that just blow your mind?

Our contemporary building habits are proving a disaster for swifts

When they come home, they come home to us in the UK, nesting in the nooks and crannies of our walls and roofs, often under the eaves. One of the most ancient orders of birds, dating back between 45 and 50 million years, they adapted to nest in our buildings in the 17th century once we’d felled the primal forests they lived in.

A whole category of birds – cavity-nesting urban birds – are either semi or exclusively reliant on cavities within our buildings to breed. For swifts, this reliance is 100 per cent, and the hole that an adult breeding pair of swifts uses as a nest is their home for life, because they’re site-loyal. Every August swifts leave the villages and towns of Britain, and the following May they return to the exact same nesting site, and can do so for 20 years.

But our contemporary building habits are proving a disaster for swifts and other cavity nesters. After their perilous journey home, many swifts find their homes blocked, and fatally break their necks and wings trying to get in, or can’t find another to use.

Soffits and fascias obstruct nest holes and stop house martins’ mud nests sticking to the surface. Reroofing is another blow, often destroying whole colonies of birds – one of the commonest places for swifts to breed is under open eaves, with the nest on top of the wall plate. Many nests are blocked and destroyed by scaffolding and renovation during the breeding season, despite this being a wildlife crime.

According to the British Trust for Ornithology, the swift breeding population declined by 60 per cent between 1995 and 2020, leaving an estimated population of 59,000 pairs. By 2024, the population was fewer than 45,000 pairs. Now, the decline trends suggest the population is sub-40,000 pairs. As a comparison, there are over five million blackbirds in the UK and an estimated 500,000 hedgehogs.

If they can’t breed, they can’t stabilise their populations. With only one brood per year yielding an average of 2.5 chicks, swifts are not a species that can “bounce back”.

There is a huge potential here for architects to help

Four species are red listed, threatened with national extinction, united in their rapid decline thanks to loss of cavity-nesting habitat: house sparrows, starlings, house martins and swifts. But as a category of birds, cavity nesters have no legal protection of their nesting sites outside of breeding season.

Modern buildings are sterile of cavity-nesting bird habitat and always will be, without swift bricks. These are simply hollow bricks that cost £34 and can be laid without expertise, though are not widely known about. As well as providing critical habitats, they are zero maintenance and sustainable.

This is why I launched the ongoing swift-brick campaign in 2022, asking the government to mandate swift bricks. I am calling on architects to support the campaign.

The UK government recently announced that the £13.2bn insulation budget will be spent in full, in the same week ministers refused to mandate swift bricks. The consequences of these decisions are siloed in politicians’ minds but intertwined in real life. Sixty-one per cent of the budget for The Great British Insulation Scheme is spent on wall insulation – one of the decline factors of cavity nesting birds.

There is a huge potential here for architects to help: what if architects incorporated swift boxes and bricks into all their designs? What if architects designed external wall cladding with swift boxes within them so that soffits and fascia had a series of holes, meaning that as our existing houses are insulated, cavity nesting habitats are created or directly mitigated?

Swift bricks can accommodate a wide range of aesthetic requirements, and when brick isn’t being used, external wooden nest boxes offer an alternative. Eight species use swift bricks and boxes: swifts, starlings, house sparrows, house martins, blue tits, nuthatches, great tits and wrens.

We can easily help our epic neighbours if we incorporate their homes into building design

The more architects recognise they’re custodians for national treasures, the more chance we have of saving this category of birds as a whole. Even if swift bricks were mandated, existing natural nesting sites desperately need preserving, and the imaginations of architects could make all the difference.

We can easily help our epic neighbours if we incorporate their homes into building design, because their home is our home. But without securing cavity-nesting habitats, these birds have no future in this country. Everyone’s most accessible nature, they are irreplaceable.

We’re talking about an iconic, beloved, 50-million-year-old species on the brink that just needs a brick with a hole in it.

Hannah Bourne-Taylor is an author and bird conservationist. She is the author of Fledgling (2022) and Nature Needs You: The Fight to Save our Swifts (2025), and the founder of The Feather Speech, a conservation campaign aimed at helping endangered birds that nest in buildings. Her petition calling for swift bricks to be mandated in all new houses in the UK has received more than 140,000 signatures.

The photo is by Action for Swifts.

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